Improvements in Down Draft Furnaces.
Year: 1892

page_text: Date of Application, 15th Nov., 1892-Accepted, 11th Mar., 1893
COMPLETE SPECIFICATION.,
Improvements in Down Draft Furnaces.
We, ORLAND DORE ORVIS and OREL DIGHTON ORVIS, both of Room 51
Commercial Bank Building, Chicago, Illinois, United States of America,
Gentlemen, 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 relates to improvements in down draft. furnaces, in which a steam
boiler as illustrated,, extends directly over the fire chamber. More specifically
stated, to that class of down draft steam boiler furnaces in which said boiler,.by an
arch or diaphragm, is isolated from the direct exposure to the burning fuel on the
grate bars and the cold air necessarily admitted through the furnace doors or other
opening in the fire chamber above the burning fuel to produce a downward draft
of the products of combustion through grate bars.
In these arch and diaphragm structures, as heretofore arranged, there is formed;
between the arch and the boiler, an air chamber, the only opening to which, like
the entire chamber, is rearward of the line of draft of the furnace, that is to say,
rearward of the line of draft of the products of combustion, as they ascend from the
grate bars and move onward to the rear of the furnace, and the result is that said
chamber is practically a dead air chamber.
In other words, such a chamber isolates all that portion of the boiler surface
immediately over the fire chamber from the draft heat to such a degree that such
surface is quite cool as compared with all other portions beyond the chamber, and
certainly the steam boiler is not heated throughout with that uniformity necessary
for the best results, nor are the products of combustion utilized to anything like the
extent they may be capable of in raising the temperature of the contents of the
boiler.
The seriousness of the objection to this isolation of heat is all the more obvious,
when it is borne in mind that, as usually and ordinarily constructed, the boiler
surface of a flueless boiler directly over the fire chamber and then isolated from
the draft heat thereof, represents about one fourth of its entire directly heatable
surface, and that although in flue boilers such as is shown, the proportions of surface
is somewhat lessened, it still remains a fact that a substantial proportion of the
otherwise directly heatable boiler surface will be practically entirely isolated from
draft heat.
The prime object of our invention is to isolate the entire surface of a steam boiler
within a furnace, and particularly that and whatever portion may be directly over
the fire chamber, from all cold air admitted and admittable to the furnace, both from
above the grate bars to produce a down draft, or from below the grate bars to
supply oxygen to promote combustion, or air for reducing the furnace heat during
combustion, and at the same time subject that entire boiler surface to all of the
draft-heat.
In other words, to subject all that portion of a steam boiler surface ordinarily
over the fire chamber of a down draft furnace, to all of the heat escaping from the
grate bars to the combustion chamber, and to do this without subjecting any portion
of said boiler surface to any cold air admitted to the furnace during its operation.
A further object in addition to securing these desirable results, is to at the same
time prevent the formation of smoke during the operation of firing or raking down
the furnace.
Another object is to ensure as nearly as may be a uniform distribution of the
heat to the boiler to be heated, as it escapes from the grate bars thereto.

page_text: A still further object is in the utilization of hollow grate bars for heating boiler
water and to prevent the accumulation of mud and the sediment therein, and at the
same time likewise free the boiler from similar accumulations, and increase the
heating surface for the water.
And finally, to secure other and minor objects by devices and combinations of
devices hereinafter described, claimed and shown in the accompanying drawing
forming a part hereof, and in which
"Fig. 1 represents a vertical transverse section of a double fire chamber furnace
embodying our invention, in connection with a boiler shown in end elevation;
C
Fig. 2, a central longitudinal section of said furnace, on the line 2-2 of Fig. 1;
Fig. 3; a detail plan view of the grate bar construction and of the mud drum of
the same;
Fig. 4, a vertical transverse section of a single fire chamber furnace embodying
our invention, with a steam boiler in end elevation; and
Fig. 5, a detail longitudinal section of the same with said boiler shown in side
elevation.
· Similar letters of reference indicate the same parts in the several figures of the
drawings.
A and A¹ indicate the side wall, and B the front end wall; C and C' the fire
chamber, and D, D' ash pit doorways, the positions of which are indicated by
dotted lines in Figures 1 and 4, and É a steam boiler all of which are of the usual
construction and arrangement.
At the rear end and rising to the top of the ash pit, is a solid wall F extending
from side wall to side wall of the furnace, upon which is supported a mud drum G
in turn supporting and in open communication with hollow grate bars H which may
be pipes in open communication at their forward ends with and attached to a
transverse header I forming a water chamber common to all of said grate bars, and
in turn supported by the walls of the furnace, as indicated in Figure 3, or in any
other suitable manner, adapted for the support of the grate bars. The grate bar
structure may be inclined and instead of having all of the bars in the same plane,
as shown, or adjacent bars may be in differing planes, the alternate bars in the same
plane.
"
At that point where there is the greatest concentration of heat upon the grate
bars in the passage of the products of combustion from the grate bar surface to the
combustion chamber, that is to say, over which all the furnace heat must pass in
escaping to the combustion chamber, said bars are preferably of larger size and
greater internal water capacity as shown at H¹, to increase the heating surface of
the boiler water.
The supply water to the grate bars is preferably taken from below the water line
in the boiler, as indicated, by the water supply pipe or pipes J, which open into the
header I, as indicated at J, shown in Figure 3, and indicated by dotted lines in
Figure 4.
:.
In its passage through the grate bars back to the boiler in the direction indicated
by the arrows in Figure 3, the water enters the mud drum G and depositing the
mud and other sediments therein, ascends through the pipe J³, directly from the
mud drum to the boiler at a point preferably above the water line, and certainly
above the plane of the grate bar supply pipes, in order to induce the necessary
circulation; it having been found in practice that the water heated by the grate
bars is of a very much higher temperature when entering the boiler from the mud
drum than when it enters the grate bars from the boiler.
The mud drum G, as shown in Figs. 1 to 4 inclusive, serves as a support for one
side or end of an arch or arches K, which arch or arches, as the case may be, in
connection with the mud drum, enclose the fire chamber or chambers, so as to
prevent the escape of any of the products of combustion therein, except downwardly
through the grate bars.
The arch or arches K may be of fire brick or other material commonly used for
such purposes and are so arranged with reference to the boiler immediately over

page_text: the fire chamber, as to provide a combustion chamber L between said arch or
arches and the boiler, to which chamber the down draft products of combustion are
conducted, as herein described.
In Fig. 1, my invention is illustrated in connection with a double fire chamber
furnace in which there is an open space between the grate bars centrally the length
of the furnace, and the arches K supported upon the grate bars H₁ at their lower
edges and joining the side walls of the furnace at their upper edges, by which
arrangement is provided at a point mid-way between the grate bars, a passage M
of the same length as the fire chambers upwardly, through which the down draft
products of combustion from the grate bars ascend into the combustion chamber
over the fire chambers and have a down draft therethrough in contact with the
boiler as they move onwardly toward the rear of the furnace.
By this construction and arrangement of the grate bars and the arches, we have
not only the advantage of subjecting the entire length of the combustion chamber
immediately over the fire chamber to the circulation of the products of combustion
by a down draft thereof, and at the same time the isolation of the boiler from cold
air admitted to the fire chambers, but the advantages due to the use of separated
fire chambers within the same general furnace structure.
These advantages will be understood when it is borne in mind that during the
firing of one chamber, the hot products of combustion passing from the other fire
chamber to the passage M, not only serve to maintain a uniformity of heat
throughout the combustion chamber and excludes cold air therefrom, but will ignite
in the passage M any waste products due to the use of fresh fuel and escaping
therefrom into the passage M, and hence before they can possibly escape into the
combustion chamber.
In the use of such double fire chambers, it may also be added that separated fire
chambers may be more thoroughly raked down and uniformly fired than could be
a single fire chamber embracing the area of both, and this, because there is less
fuel to handle at a time and more time to do the raking and firing without reducing
the temperature in the combustion chamber than is possible by the use of a single
fire chamber.
1
Single fire chambers, however, being frequently desirable, are provided for by
our invention as shown in Figures 4 and 5, in Figure 4 of which is shown, a
single fire chamber, access to which is provided for through furnace and ash
pit doors at the front end of the furnace, as indicated by the dotted lines therein.
In this construction, there is a space between the side grate bars H¹ and the
walls of the furnace, which bars support the arch K enclosing the fire chamber,
the products of combustion from which fire chamber after passing downwardly
through the grate bars, ascend to the combustion chamber L through the
passages M at each side thereof and for the entire length of the fire chamber.
In order to promote a uniform distribution of the productions to the combustion
chamber L when such distribution is found necessary, there may be provided below
the grate bars longitudinally thereof, and transversely of their centre a deflector N
converging at its upper end to an edge and consisting of brick or other suitable
material, which deflector may also be utilized as a supply to the products of com-
bustion of heated air, by means of one or more chambers P formed therein,
communicating with the outside air and provided with openings P¹ in the ash pit,
for discharging its contents, the heat in the ash pit serving to heat said deflector
and therefore its contents.
In this connection, it is proper to observe that instead of utilizing said
deflector for supplying heated outside air, it may be connected with the rear
of the furnace to draw off and return to the ash pit any unconsumed products of
combustion.
In Figure 5, we have provided means for drawing all the products of combustion
from the grate bars to the forward end of the combustion chamber immediately
over it, whereby all products of combustion are required to traverse the full length

page_text: of said combustion chamber, and to this end, the grate bars extend transversely of
the furnace, which latter is provided with side doors for firing and for the ash pit,
as indicated by dotted lines, and terminating the grate bar surface at a point
forward of the front end or wall of the furnace structure, the arch in this-con-
struction extending from side-wall to side-wall of the furnace and downwardly to
and supporting it from the grate bar H', the rear end of the arch being supported
by the wall F, which instead of including the mud drum, is above the grate bar
surface to afford such a support.
As in the construction shown in Figure 5, it may be observed that the mud drum
may be omitted in the several other constructions shown in the drawings, or, on the
other hand, the mud drum may be used in the construction shown in Figure 5, 'as
shown in said other figures.
In conclusion, it may be stated that our invention is not limited to the details
shown, although they illustrate what we believe to be the best construction
embodying our invention, for, obviously, it would be no departure therefrom to
vary these details and arrangement, so long as in a down draft furnace cold air
admitted to the 'fire chamber is isolated from the combustion chamber and there is
immediately over the fire chamber a portion of that combustion chamber through
which there is a direct draft of the products of combustion from the grate bar
surface of such furnace.
Neither is our invention 'limited to its use in connection with a steam boiler, such
as is shown, for, obviously, it is adapted for and can be applied without invention,
to the fire chamber of a stationary or locomotive engine, or any engine wherein
'there is over the fire chamber or at the sides thereof, a water chamber in direct
communication with the contents of that boiler, or to any furnace over the fire
chamber and which has a heating oven of any character or a portion of such a
heating oven or hot'air chamber.
Having now particularly described and ascertained the nature of our said inven-
'tion and in what manner the same is to be performed, we declare that what we
claim, is:
1: In a down draft furnace, the combination of the fire chamber and combustion
chamber separated from but directly over the fire chamber, and a draft passage
through which the down draft products of combustion 'are conducted into said
combustion chamber at a point forward of its rear end during their'onward passage
towards the rear end of the 'furnace, substantially as described.
2: In a down draft furnace, the combination of a combustion chamber 'or
'chambers, separated from but directly over the fire chamber, and a direct draft
"passage at the side or sides of said fire chamber, through which the downdraft
products of combustion are conducted into said combustion chamber in their
onward passage towards the rear end of the furnace, substantially as described.
3: In a down draft furnace, the combination of two or more fire 'chambers, a
combustion chamber separated from, but directly over said fire chambers, and a
draft passage between said fire chambers conducting the down draft products of
combustion from the said fire chambers directly to the over head combustion
chamber, 'substantially as described.
4: In'a'down draft furnace, the combination with the fire chamber, a combustion
'chamber directly over said fire chamber, an arch or diaphragm separating said
chambers, and a direct draft passage or passages between said arch and the wall or
walls of the furnace, through which the down draft products of combustion from
the grate bars are conducted directly to said combustion chamber, whereby said
'combustion chamber throughout its length is subjected to direct draft heat in the
passage of the products of combustion from the fire chambers to the rear portion
of the furnace, substantially as described.
5: 'In a down draft furnace, the combination of 'the 'fire chamber, an archlike
structure enclosing the same, a combustion chamber directly over said grate bars,

page_text: and an updraft passage directly conducting the downdraft products of combustion
from the grate bars to the forward end of the combustion chamber immediately
over the fire chamber, substantially as described.
ORLAND DORE ORVIS.
OREL DIGHTON ORVIS.
Haseltine, Lake & Co.,
45, Southampton Buildings, London, Agents for the Applicant.