Note: Descriptions are shown in the official language in which they were submitted.
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Back~round of the Inventlon
Known fireplace forms include an enclosure or housing on
the outside ofand spaced from the sides, back, and top of a firebox
so as to define a chamber between the firebox and the enclosure
in which fresh air is heated. Typically, the enclosure has air
inlets for the intake of air at its bottom and air outlets at its
top for discharging the heated air. The outlets are often connected
to appropriate air ducts for distribution of the heated air into
a room. In many instances, natural convection within the chamber
was sufficient to effect the circulation of air therewithin. In
other instances, blowers have been utilized to aid in circulating
the air. Reference may be made to U.S. patent 2,642,859 for
disclosure of such a fireplace form. Other fireplace forms, such
as are disclosed in U.S. patent 252,064 were intended for use
in down-draft fireplaces. Down-draft fireplaces, however, are not
widely used as residential fireplaces.
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In other known fireplace forms, attempts
have been made to increase the heating efficiency of
the fireplace by circulating air through so-called
"heat flues". Reference may be made to such U.S.
patents as 2,165,661, 2,331,17~ and 2,549,365 for
examples oE such fireplace forms with increased heat
transfer abilities. Generally, these prior art fire-
place forms did increase the thermal efficiency of the
fireplace, but still a significant part of, if not the
majority of, heat from the fire was wasted.
Summary of the Invention
Among the several objects of this invention
may be noted the provision of a fireplace form which
has increased thermal efficiency. Other objects and
features of this invention will be in part apparent
and in part pointed out hereinafter.
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In a first aspect, a fireplace form of this
invention comprises a firebox adapted to contain a
fire of burning logs or other fuel having an open front,
a back wall, and a pair of side walls at opposite sides
of the back wall and extending toward the open front.
This firebox has main flue outlet means generally at
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its top for communication with a chimney flue. The
firebox has at least one aperture in its back wall
intermediate the bottom of the firebox and the main
flue outlet means. The fireplace form further in-
cludes duct ~eans on the back side of the fireboxin communication with the aperture and with the chim-
ney flue, this aperture and duct means constituting
auxiliary flue means for at least partially ducting
away smoke and other products of combustion from the
firebox. Other means are provided for circulating
fr~sh air over the sides and back of the firebox and
over the duct means so as to be heated and for ex-
hausting this heated air into a room. The fresh air
cixculating means comprises an outer housing spaced
from the outside of the firebox defining a chamber
between the firebox and the outer housing. This
chamber has inlet means for the intake of fresh air
and outlet means for the discharge of heated air and
further comprises a fresh air conduit disposed ver-
tically within the duct means having an inlet at itslower end for the intake or fresh air and an outlet
at its upper end for the discharge of heated air
into the room via the outlet means.
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In a second aspect, a fireplace form of this
invention comprises a firebox adapted to contain a fire
of burning logs or other fuel, having an open front. A
housing is spaced from and surrounds the firebox thereby
to define a chamber between the firebox and the housing.
The fireplace form further has intake means in the sides
of the housing for the intake of air into the chamber for
being heated and outlet means for the discharge of heated
air. Air conduit means in the firebox adjacent the upper
front portion thereof extends generally from side to side
of the firebox for heating a portion of the air in the `~
'~ chamber. Means for channeling at least a portion of the
air entering the chamber via the air intake means to the
conduit means is also provided.
Brief Description of the Drawings - -
Fig. l is a front perspective view of a fire-
place form of this invention with parts broken away to
show the circulation of smoke to the chimney and the ~`
circulation of air to be heated;
Fig. 2 is a back perspective view of a fire-
place form of this invention with other parts broken
away to show the flow of air as it is heated;
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Fig. 3 is a vertical section taken on iine
3--3 of Fig. 2;
Fig. 4 is a vertical section taken on line
4 -4 of Fig. 3;
Fig. 5 is a vertical section taken on line
5--5 of Fig. 3;
Fig. 6 i~ a horizontal section taken on:line
6--6 of Fig. 5, and
Fig. 7 is an,enlarged cross-sectional view of
a smoke duct taken on line'7--7 of Fig. 2.
. Corresponding reference characters indicate
corresponding parts throughout $he several views of the
drawings.
Description of a Preferred Embodiment
- . ' Referring now to.~he drawings, a f~replace
form of this invention, indicated in its entirety at 1,
is shown ,to include a firehox 3 for containing a fire
of burning logs (not shown) or other fuel ~eOg., natural
gas logs or the like). The firebox has an open front 5,
a back wall 7, lef~ and right side walls 9~ and 9R, and , ,~
a top wall 11. The side and back walls at least partially
converge in upward direction to form a series (e.g.,
three) of main flue outlets 13 in ~op wall 11 for com-
munication with a chimney flue 15. The flue outlets are
' connected to the chimney flue via flue ducts 17 and a chim-
ney plenum box 18. It will be understood, however, that
in place of the three main flue outlets 13, the firebox
wall~ could converge to form a single throat (not shown~
generally above the fire in the firebox with the throat
leading directly to the chimney flue lS.
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In accordance with this inven-tion, firebox 3
has at least one auxiliary smoke aperture 19 (three
of~such apertures are shown) in back wall 7 intermediate
the bottom o~ the firebox and main ~lue outlets 13. A
respective auxiliary smoke duct 21 is sealingly secured
(e.g., welded) to the outside of back wall 11 surrounding
each aperture 1~, thes~e smoke ducts leading to plenum box
18 so as to duct smoke and other products of combustion
from the interior of the firebox to chimney flue 15 and
so thus constitute auxiliary flue means for at least par~
tially ducting some of the smoke from the firebox. A
housing, generally indicated at 22, of sheet metal or
other suitable material is spaced from the outside of
the firebox and de~ines a cham~er 23 between the housing ~ 7
and the fire~ox. 'llhis housing has air inlets or intakes
25L and 25R at its lower front portions for the intake -
of fresh air from a room which is to be heated and air
outlets 27L, 27R at the upper rear portion thereof for
discharge of heated air. Preferabiy, the area of the ;~
outlets is somewhat larger than the inlets. It will be
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understood that outlets 27L, 27R may be in communication
with air ducts (not shown) for the proper distribution
of heated air into a room or rooms. As air enters chamber
23, it is heated and rises within the chamber because of
25 natural convection and is discharged via outlets 27L and ~-
27R. The exterior of housing 22 may be covered with
insulation panels (not shown) to prevent the loss of heat
from the housing. The use of smoke ducts 21 appreciably
increases the heated surface area of firebox 3 and thus
aids in heating the air in chamber 23.
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More particularly, firebox 3 may be made of
heavy-gauge sheet metal or other suitable material~ or
may be ~ade of cast aluminum or cast iron. When made
of cast aluminum, heat transfer from the firebox to the
air in chamber 23 is, of course, enhanced.
Side~alls 9L, 9R are shown to angle inwardly
from tneir front edges to their rear edges so that the
interior of firebox 3 is narrower at its rear than at
its front. Back wall 7 has a lower, generally vertical
portion 29 extending up from the floor of the firebox, a
generally horizontal ledge 31 extending forward from the
top of the vertical portion 29, and an inclined upper
portion 33 angling upwardly and forw~rdly from ledge 31
to intersect top wall 11. Apertures 19 are formed in
vertical wall portion 29 and in ledge 31 at the level of
the ledge so as to be positioned at about the preferred
level of a fire within the firebox. Auxiliary smoke ducts
21 are sealingly secured te.g., welded) to the vertical
wall portion 29 and to ledge 31 so as to surround and seal
apertures 1~. Preferably~ a portion of the lower end of
each duct 21 is removed so that the duct rests directly
- on ledge 33 and so that the duct surrounds both the por-
tion of aperture 19 in wall 29 and in ledge 31.
As bést shown in Figs. 2 and 7, smoke ducts 21 are secured
to housing 22 in heat transfer relation. Preferably, the
ducts are welded to the back wall of the housing as indi-
cated at 35 tsee Fig. 2). Thus, the housing serves as a
heat transfer surface for conducting heat from the ducts and
for aiding in heating air in chamber 23.
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An optional inner air duct or conduit 37 may
be provided within each smoke duct 21. As best shown
in Fig. 2, each air duct 37 extends below its respective
smoke duct 21 and its bottom end thus constitutes a
fresh air intake in communication with chamber 23. The
air duct extends-vertically in the smoke duct and-exits
vertically through the smoke duct for exhausting air into
the upper part of chamber 23 for discharge from outlets
27L, 27R. I~ will be understood that the bottom of
s~oke duct 21 is sealed with respect to the air duct
- inlet and that smoke duct Zl is seal~d with respect to
the ~ir duct at the top of the air duct. As best shown
; in Fig. 7, air ducts 37 are of smaller cross~section
than their respective smoke ducts 21 and are preferably
welded to their smoke ducts as indicated at 39 to enhance
the transfer of heat into the air duct from the smoke
duct. As hot smoke and other products of combustion are
drawn through apertures 19 and through smoke ducts 21,
air ducts 37 are heated so as to heat the air therewithin.
As this air is heated it rises within the ducts 37 by
means of natural convection and hus causes air to con-
tinuously flow into the bottom of the air ducts to be
heated and to be exhausted from the top of the air ducts.
The use of the~e inner air ducts appreciably increases
thé heat transfer area of the smoke ducts and thus in-
creases the thermal efficiency of the ~ireplace of this
invention.
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To further increase the heat tran.sfer area
of the fireplace of this invention, a serie~ of generally
vertical fins 41 are secured in heat transfer relation
(e.g., welded or cast in place) to the outer face of wall
portion 33 of back wall i of the firebox. Baffles 43 are
secured to the upper ends of these fins and to smoke
ducts 21 so as to channel air upwardly over w~11 portion
33 and over fins 41 for being heated and for being dis-
charged toward outlets 27L, 27R. Preferably, baf~les 43
are spaced from the back wall of housing 22 so as to per-
mit air within chamber 23 to rise along smoke ducts 21
for being heated thereby. Smoke ducts 21 have fins 45
secured thereto so as to increase their heat transfer
area and to thereby aid in heating the air within cham-
ber 23.
As best shown in Figs. 1-6, a so-called air
trough or conduit 47 is provided at the upper front por-
tion of firebox 3 for heating a portion of the fresh air
drawn into chamber 23. The top of firebox 3 is, of
course, one of the hottest areas o~ ~he firebox. Trough
47 is shown to extend from side to side of the irebox and
to be open on its ends constituting inlets for the ~rough.
Top wall 11 overlies the trough, but does not completely
close it off. More particularly, a slot 49 extends from
side to side of the firebox above the trough and consti-
tutes an outlet for the trough. A respective baffle 51L,
51R is secured to the outside of respective walls 9L, 9R
to span be~ween firebox 3 and housing 22 so as to form a
duct or conduit leading from a respective air intake 25L,
25R to a respective open end or inlet of trough 47. As
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air within trough 47 is heated, it rises out of slot'49, . '
and draws more air to i~g inlets. In this manner a .least
a portion of the fresh air entering chamber 23 is drawn
upwardly and guided toward the inlets to trough 47 by
,baffles 51L, 51R for being heated in the trough.
It will be understood that the fireplace form ' .
1 of this invention may be a prefabricated unit adapted
to be installed in a residential house or the like merely
by setting in on a properly prepared base or hearth and
connecting its chimney flue outlet to a flue in the house. ':
Of course,the exact design and shape of the fireplace
form in this invention may be varied considerably depend- .ing on the particular installation. It will further be ~ .
understood that appropriate dampers may be incorporated
in chimney flue 15, in flue ducts 17, or in.;~moke ducts 21.
In view of the above, it will be seen that the
., several objects of the invention are achleved and other
advantageous results attained.
As various changes could be made in the above
constructions without departing from the scope of the in- -
vention, it is intended that all matter contained in the,
above description or shown in the accompanying drawings
~hall be interpreted as illustrative and not in a limit-
ing sense.
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