Note: Descriptions are shown in the official language in which they were submitted.
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Bauder/4-CDA,USA.W
BACKGROUND OF THE INVENTION
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Field of the Invention
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The invention relates to an andiron for supporting
; 10 logs on a domestic fireplace hearth.
Prior Art
It is well known that open domestic fireplaces
using common basket type grates to support fuel are rela-
tivel~ ineffective for heating a room. Common grates suspend
the fuel a short distance above the hearth to increase air
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flow through the fuel, but such grates remove heat by con-
duction and set up convection currents which pass heat up
the chimney. Sides of the grate also restrict radiation of
heat into the room from high temperature portions of the
` fire.
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Some mechanical devices are available to improve
heat transfer to the room, one example being a double walled
fireplace that circulates air into the room from spaces
between the double walls to improve heat transfer, but this
type of device is expensive to construct and cannot be
easily incorporated into an existing fireplace. Tubular -
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grates to support fuel and to heat air passing through the
tubes into the room can be fitted into an existing fireplace,
but detract from the appearance of the fireplace and also
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cool the fire to the detriment of combustion. I-t is
considered that a major factor contributing to the in-
efficiency of common fireplaces is that most of the heat
that is transfered to the room is transfered by radiation,
but typically the portion transfered by radiation is only a
small portion of the total heat from the fire. The remaining
heat is removed from the fire by conduction and convection,
most of which tends to escape up the chimney. Furthermore
a portion of heat radiated from the fire is radiated to
walls of the fireplace, which is then lost because convection
currents cool the heated walls and pass up the chimney.
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It has already been recognized that if the pro-
portion of radiant heat transfer is increased, the heat
radiated to the room will increase, thus increasing effec-
tiveness of the fire. Andirons or grates have been designed
to hold fuel so that a greater portion of heat is trans-
fered tc the room by radiation from the burning surfaces
-thereof, but when using some of -these devices it has been
found that sometimes it is difficult to maintain satis-
factory combustion and effective radiation over extendedperiods of time
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SUMMARY OF THE INVE~TION
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The present invention provides an andiron with im-
proved control of combustion of the fuel, which reduces heat
3 loss up the chimney by convection currents, and improves
radiation of heat of combustion directly into the room to be
heated. Furthermore a relatively large fire is not required
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to produce a large radiant heat source, and commonly the
fire is easy to light and requires little attention after
initial lighting
An andiron according to the invention supports on
a hearth first and second primary fuel banks in an inverted
V-position, and has a baffle member, posîtioning members and
frame means. The baffle member is spaced at a ba~fle height
above the hearth and has spaced, generally horizontally dis-
posed first and second edges which define a baffle width of
between about 25 percent and 50 percent of the baffle height.
First and second positioning members are positioned below the
baffle member and are spaced laterally relative to each other `
and the baffle member. The frame means connect the ba~fle
member to the positioning members so as to form a self-
suppor~ing framework having at least one open end~ and in ~`-
which the baffle member and first positioningmember on one ~ f.
8ide of the frame are positioned so that the first fuel
bank extends between the first edge of the baffle member
and the positioning member, and is inclined to the vertical
at an an~le of incllnation of between 15 and 30 degree~q
The second positioning member on the opposite side o~ the `~
fr~ne is positioned relative to the second edge of the
baffle member so as to support the second fuel bank on the
opposite side of the frame at a similar angle. When correctly
supported on the andiron, the fuel banks form a generally
inverted V.
In operation, secondary fuel is placed on the hearth
between the inclined primary fuel banks so as to leave air
passages between the primary and secondary fuel and the
baffle member. The air passages and the space above the ;
baffle member between the inclined fuel banks form a trian-
gular-sectioned combu~tion ~one. Combustion is established on
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opposite faces of the primary and secondary fuel and heat
is radiated between the burning faces to maintain combustion
and radiate heat to room. Most of burning takes place on
inner faces of primary fuel with negligible burning on
the outer faces, thus reducing convection lossesup the
chimney.
A detailed disclosure following, related to draw-
ings, describes a preferred embodiment of the invention i~
which is capable of expression in structure other thanthat particularl~ described and illustrated.
DESCRIPTION OF THE DRAWINGS
Fig. 1 is a fragmented perspective of an andiron
according to the invention supporting four logs in a hearth
to serve as primary fuel banks~
; Fig. 2 is a perspecti~Te of the andiron of Fig. 1, the logs being removed,
Fig. 3 is a fragmented elevation of -the andiron
of Fig. 1 showing logs supported thereon,
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Fig. 4 is a perspective of an alterna-tive andiron,
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Fig- 5 is a simplified top plan of an alternative
baffle member.
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DETAIL~D DISCLOSURE
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An andiron 10 according to the invention supports
first and second pairs of logs 11 and 12 on opposite sides
thereof. The andiron stands on a hearth 15 and is adjacent ','
a vertical fireplace rear w,all 16. Oppositely facing fire- '',
; 10 place side walls are not shown and these can be some dis~." .
tance from the andiron and logs. The andiron has a frame ~'
- means 19 which includes a pair of similar open frame members '
21 and 22, a baffle member 23 and first and second spaced ;~
positioning members 25 and 26. The frame member 21 is a
; 15 truncated, generally inverted V-shaped bar 2~ having an ~',
upper portion 29, and similar leg portions 31 and 32 with "'
lower ends 33 and 3~ respectively. The frame member 22 is
similar and thus the two members 21 and 22 together form a
frame means having a pair of similar open frame members
which each include generally downwardly curved bars which ' -~
extend to the lower ends thereof. The lower ends of the
two frame members are disposed within a horizontal plane and '~ '
are adapted to contact the hearth 15 for supporti~lg the an- ,
, diron thereon. ,'
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The baffle member 23 a generally horizontally
disposed, rectangular plate which extends between upper por-
tions of the frame members and has spaced first and second
horizontal edges 37 and 3~ which support the log pairs ''
thereon~ The first and second positioning members 25 and -
` 26 extend between leg portions of the f'rame members and are
`,3 positioned below the baffle member. The members 25 and 26
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are spaced laterally relative to each other and the ba~fle
member so that the first posi-tioning member on one side of
the frame is positioned so that the log pair 11 extends
between and is supported on the first edge 37 of the baffle
member and the positioning member and is inclined to the
vertical at an angle of inclination 41, Fig. 3 only, which
is between 15 and 30 degrees. The second positioning member
26 on the opposite side of the andiron is positioned rela-
tive to the second edge 3~ of the baffle member so as to
support the second log pair on the opposite side of the frame
at a similar angle 42. Thus when the logs are correctly
supported on the andiron the logs form a generally inverted
V which, together with the hearth 15, defines a triangular
shaped combustion zone 44 therebetween.
The positioning member 25 has upwardly and out-
wardly turned end port.ions 47 and 4~ secured to the frame
members so that the positioning memberextendsdownwardly
and inwardly from the frame member. This forms a cradle
in which the pair of logs 11 is supported and the end por-
tions restrict lateral movement of the logs supported there-
on. As best seen in Fig. 3, when supported on the respec-
tive edge of the baffle member and the respective positioning
member, the log pairs are inclined so as to be parallel to
the adjacent leg por-tions which similarly res-trict lateral
movement of the logs. The positioning member 26 has
` similar end portions and thus it can be seen that the end
portions of the positioning members serve as means adjacent
ends of the positioning members to restrict lateral move-
ment of the logs supported on the positioning members.
Referring to Figs. 1 and 3, two pairs of logs 11
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and 12 in an inverted V-position serve as first and second
primary fuel banks. ~ig. 1, shows two log pairs of the same
size and shape, such as common round, uniform artificial
logs made from compressed wood waste. Other fuel can be
substituted, for example several small logs of different
sizes may be used to fill the spaces on each side of -the i
andiron to form two primary fuel banks that touch or nearly
touch at the apex and are inclined at the desired angle.
The material may also be newspapers rolled into "logs" of
up to five inches in diameter. Whatever material forms
the primary fuel banks, there should be no large gaps in
either side so that inner faces 49 and 50 of the first and $
second fuel banks present essentially unbroken surfaces
which when burning form radiant faces. Secondary fuel 51
is placed on the hearth 15 between the primary fuel so as
to form air spaces 53, 54 and 55 within a lower portion of
the combustion zone 44 below the baffle member. An air space ;
57 above the baffle member and between upper ends of the
primary fuel banks is adjacent an apex 56 of the fuel banks,
ie where upper inner corners of -the fuel banks touch or al- ~-
most touch each other. ~ ~
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The volume and shape of the secondary fuel is
chosen so that the air spaces 53 and 54 are left between
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the primary and secondary fuel and the air space 55 is
lef-t between the secondary fuel and the baffle memberO
These three spaces and the space 57 above the baffle plate
between the primary fuel banks form the triangular shaped
combustion zone 44. Varying the volume of secondary fuel
varies the characteristics of combustion and provides a means
of compensating for the type of fuel used, its moisture con- ;;~
tent and the fireplace draw. A little experimen-tation may
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be necessary to ascertain the best volume of secondary fuel
which, oncecorrectly selected, may require occasional re-
plenishment during the combustion of the primary fuel. Figs.
1 and 3 show secondary fuel of short blocks of the logs
made from compressed wood waste, but the secondary fuel
can be logs that are approximately the length of the baffle
plate - or even~lumps of coal.
OPERATION
In operation, when using logs made from compressed
wood waste the two primary fuel banks are established by
settin,g up preferrably two logs on each side of the
andiron so that the logs are supported on the hearth 15,
the first and second edges of the baffle member and the
first and second positioning members. Secondary fuel is '-
placed on the hearth under the baffle member and between
20 the primary fuel banks.- Kindling and paper are placed in ;~
the combustion zone and lit and~ usually after a few minutes,
combustion of the primary and secondary fuel commences and
the convection currents thus set up cause the combustion
air to flow up the inner faces of the primary fuel banks
2~ to escape adjacent the apex. Because the inclination of the
~uel produces more than adequate draft the baffle member
reduces the flow of air through the combustion zone and in-
creases turbulence in the flow. This controls air flow
and turbulence to an amount which causes almost all the
o~ygen to be completely removed from the combustion gases
and reduces the flow of gases up the chimney.
At the proper angle of inclination of the primary
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fuel, burning occurs only on the inner faces 49 and 50 of ;~
the primary fuel banks adjacent the andironj and the outer
faces of the primary fuel banks remain rela-tively cool so ;~
that radiation to the fireplace and convection currents
flowing over the outer faces of the fuel banks are relati~e-
ly insignificant. Much of the radiant heat generated on
one burning inner face of one primary fuel bank is radiated
to the opposite burning inner face of the primary fuel
bank, the secondary fuel, the baffle member or the rear ;~
wall of the fireplace so that a high temperature, relatively
stable and uniform fire is maintained throughout the combus~
- tion zone. Thus there is absorption of radiant heat from
an opposite burning face, which heat is re-radiated back
into the combustion zone so as to increase temperature
within the combustion zone. Since only a little heat es-
capes laterally through the primary fuel banks, the tem-
perature of the burning surfaces must rise and heat escapes
from the combustion zone only by radiation directly into
the room through the opening at the front. It is a well
known principle of physics that the radiant heat depends
on the fourth power of the temperature, and if heat cannot
otherwise escape, the temperature will rise until the heat
is transferred into the room by radiation. Thus in effect
the primary fuel banks serve also as thermal insulators to
reduce heat losses by conduction and convection which in-
evitably results in a higher transfer of heat by radiation. -
~hen operating properly, from the room the fire within the
combustion zone appears as a fairly uniform red triangular
area defined partially by unburnt outer surf~ es of the
primary fuel banks.
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Because the primary fuel burns from one side only9
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it tends to produce a long-lasting fire which burns uni-
formly with little attention. As the fuel burns, the inner
faces ~9 and 50 of the primary fuel banks are burned away
gradually and weight of the remaining portions of the
primary fuel tends to move the primary fuel banks in to-
wards the andiron to maintain shape of the air spaces
53,5~9 55 and 57 as aforesaid. Ash falls from the inclined
burning faces t~o expose fresh radiant heat sources, thus
reducing a tendency of the ash to choke the fire by restric-
ting air flow, similarly to what happened in time with someprior art gratesO It has been found that four logs made
from compressed wood waste have burned for more than four
hours without attention, and newspapers rolled into four ~ -
imitation logs of about 5 inches in diameter can burn for
about three hours~ and when burned are reduced to a fine
white ash.
DIMENSIONAL GONSIDERATIONS
To achieve the effect outlined previously, there
are limits to the angles of inclination of the primary
fuel banks, and limits to baffle member height and length ^
in proportion to fuel length. These limits determine many
of the dimensions of the andiron. The angle of inclination
of the primary fuel banks is preferably between about 20
and 25 degrees to the vertical, but some fuels burn satis-
factory when inclined to the vertical a-t angles of between
15 and 30 degrees. If the angle of inclination is in excess
of about 30 degrees, ie less s-teeply inclined, the combus-
tion gases tend to flow around edges of the primary fuel
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banks, or through gaps between logs in each fuel bank. This
undesirable gas flow would set up convection currents on the
outside of the primary fuel banks, radiating heat to the
fireplace, removing heat from the combustion zone and
decreasing the radiant heat output. If the angle of in-
clination of the primary fuel is much less than about 15
degrees to the ~ertical, ie more steeply inclined, the logs
may tip outwards, thus destroying the effectiveness of the
fire, and also the space for secondary fuel is reduced and
the secondary fuel may be consumed too quickly.
The baffle member is spaced above the hearth at a
height 46 of between 60% and 70~0 of the fuel length9 but in
some cases the andiron performs satisfactorily if the baffle
15 ~ member is positioned at a height of about 55% to 75~0 of the
fuel length. If the baffle member is positioned too high
above the hearth, draft restriction is reduced because
strong convection currents can be created in the combustion
zone below the baffle and excess air will flow into the com-
20 bustion zone. If the baffle member is positioned too close ;y
to the hearth~ the space for secondary fuel is reduced and
the relatively uniform combustion of the primary fuel banks
is not achieved.
The baffle member has a preferred length of be-
tween 75% and ~0~0 of the fuel length~ but -this can be varied
under conditions as particularized below. If the baffle
member is too short in relation to the fuel length, the
volume of the combustion zone is reduced in relation to the `
3 are.L of radiation and heat radiated to the room can be such
that the combustion zone is maintained below the desired :
combustion ternperature. If this were the case~ the fire
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would in effect cool itself by radiating excessively and
thus would never attain the required temperature for good
combustlon~ If the baffle member is too long in relation to
the length of the fuel, heat from the rear of the combustion
zone adjacent the fireplace wall cannot be radiated effec-
tively into the room. In some fireplaces that are open on
two opposite sides, eg, a fireplace positioned away from
walls of a room, it may be desirable to have radiation
from both ends of the andiron, and in this case -the length
of the baffle member could be increased to greater than the
fuel length and the desired interaction could be maintained~
Wllen the primary fuel length, angle of inclination of the
primary fuel and the baffle member height and length are
chosen, other dimensions of the andiron are determined. ~;
~5 The baffle member has a width 52 defined by the edges 37
and 38 and the positloning members are positioned so that ~-the desi~ed angle of inclination is achieved and the pri~
mary uel banks nearly touch at the apex of the triangle. i;~
For a fu~l length of 12 inches, typical dimensions could be: ~is
angle o~ inclination of
primary fuel banks to vertical - 23 degrees `
height of baffle member - ~ inches
width of baffle member - 2.75 inches
length of baffle member - 10 inches
horizontal spacing between
positioning members - 6 inches
An alternative approach is to determine the angle of the
primary fuel banks by referring to the baffle width 52 in
rela~ion to baffLe height 46. Assuming upper ends of the
logs on one side of the mber 23 touch or almost touch upper
ends of logs on the opposite side) for a mean angle of in-
clination 41, 42 of the logs of about 23 degrees, and a
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mean baffle member height 52 of about 65 percent of the
fuel length, the width 46 would be between abou~ 25
percent and 50 percent o~ the baf~le height 52. Thick-
ness of the baf~le member is determined primarily by
fire resistance requirements rather than strength re-
quirements and is usually less than 25 percent of the
width 52. ,
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ALTERNATIVES AND EQUIVALENTS
If the rear wall 16 of the fireplace is curved3 , '
or is unsatisfactory for other reasons as a radiating sur~
15 face to close the far end of the andiron, a rear,plabe ~'
59 extending between leg portions and upper portions of the `',
frame rnember 22 can be fitted. The plate 59 is shown in ; ;
broken outline in Fig. 2 and closes the far end of the
andiron and provides a surface to radiate heat into the room. ' ,~
In any event, at least one end of the frame means 19 should
be open to radiate heat into the room. ~'
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The andiron 10 as previously described is simple -
to make and uses only one pair of positioning members ~,1;~,"~, ,
extending between leg portions of the frame members. If
desired1 two or more pairs of positioning members can be ",~
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fitted but this has not been found necessary. Alternative ,~.
means of supporting logs at the desired angle and locating
the logs laterally are envisaged as in Figs. ~ and 5.
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An alternative andiron 60 is shown and this differs
from the andiron 10 of Fig. 1-3 by substituting alternatively
shaped frame means and positioning members. The andiron `
60 has a frame means 61 including a pair of similar frame
members 62 and 63~disposed within spaced parallel vertical
planes. The frame member 62 is a generally inverted u-shaped
bar 6~ having spaced leg portions 65 and 66, an upper
portion 67 and corner portions 6~ and 69. First and
second positioning members 71 and 72 are straight rods
and extend be1,ween the leg portions of the frame member$9
and a baffle member 7~ extends between the upper portions
of the frame members. The baffle member has generally ``
lS horizontally disposed first and second edges 75 and 76
which, in combination with the positioning members, support
the logs at similarly inclined angles as shown for the andiroh
` 10 in Fig. 1.
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The corner portion 69 and an opposite corner
portion 77 of the member 63 extend upwardly and outwardly
from a plane 7~, shown in broken outline7 which connects
the adjacent edge 76 of the baffle member and the adjacent
positioning member 72. Logs supported on the members 72
and 7~ lie generally parallel to the plane 7~ and thus are
positioned between the opposed corner portions 69 and 77
` which restrict lateral movement of the logs supported on
and extending between the particular edge of the baffle
member and positioning member. The corner portions on the
opposite side of -the andiron similarly cooperate with logs
positioned therebetween. Thus the corner portions are equi-
valent to the turned up ends of the positioning members 25 and
` 26 of Fig. 1 and serve as means adjacent ends of the position--
ing members to restrict lateral movement of the lgs
ported on the positioning members.
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Other frame means can be devised to cooperate
with the baffle member and positioning members to provi~e
the particular relative positions necessary to :.
. support the primary fuel banks at the required angle, and to
form a self-supporting framework, having at least one open end.
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The baffle members 23 and 74 of Figs~ l and 4
are shown as rectangular plates with straight parallel edges
and the frame support memberis restrict lateral movement .
of the logs. For most ~uels, spaces between the logs
and edges of the baffle members are sufficient to re-
strict air flow through the andirron and pas~ the
ba~1e member without completely eliminating this air
flow. I the fuel has flat faces resting against the
- straigh~ edges of the baffle member~ air flow restric- .
j tion past the baffle member would be increased and thus
additional clearance openings in the baffle member or `
along edges of the baffle member would likely be re-
quired. If the andiron were to be used only for the
burning of logs made from compressed wood waste or rolled
newspaper logs, where the nurnber, size and shape of the
logs is fairly closely controlled, it might be an advantage
to scallop or otherwise change the edges of the baffle
member to be generally complementary to the fuel to be
used. This could improve draft restriction and one example
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is to be described.
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- An alternative baffle member ~O is for use with
two similar spaced frame means and positioning members in accor-
dance with Figs. l or 4 or equi~alents thereof. The member ..
O has a pair of spaced similar scalloped edges ~2 and ~3 -.
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having cut-outs ~4 which are complementary to cylindrical
logs to be retained therein. This structure provides
lateral restriction of upper ends o~ the logs and improves
draft control~
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