Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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~ is invention relates to stoves particularly to
wood-burning stoves.
BACKGROUND OF THE INVENTION
Before modern technology and improved standards of
living brought oil, gas and electrical heating into normal
domestic use, heating was principally by means of burning
coal or wood. More recently, increased demand for fossil
fuels due to still further increases in standards of living
and increase in population has led to an alarming depletion
of reserves. This, in turn, has led to a search for new
technology for power production and to strenuous efforts to
improve the efficiency of previously known power production
methods.
Wood and coal have traditionally been burnt in open
fireplaces to produce heat. In the past, this has been very
wasteful of material because a very large amount of heat was
lost up the chimney. Rather better but by no means efficient
were free-standing furnaces for burning coal or wood often
having a metal casing as a chimney, a large part of which
could also radiate heat into the surrounding building. Also
in use were enclosed stoves projecting into a room from an
existing fireplace leading to a masonry chimney.
Only very recently has much research been carried
out on what are the considerations in efficient burning of
wood or coal in domestic stoves. Among these considerations
are the speed of combustion, the heat of combustion, the
amount and direction of a draft of combustion air or oxygen,
the temperature gradient up the chimney, the recovery of heat
from the chimney, the recovery of heat from the region of the
fire box, and the like.
With some of these considerations in mind,
combustion units have been designed which when fuel is
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burning therein, automaticalLy set up a flow of circulating
air around the combustion zone. Thus, cool air i5 drawn in
from the room, warmed and returned thereto in addition to
normal radiation from the fire. Such units are often open
grates.
Wood-burning stoves have particular problems due to
deposition of creosote. Creosote deposition is related to
combustion temperature.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a stove
having improved means to cause circulation of room air
therearound with resultant warming of the room air.
It is another object of the invention to provide
passage means for the flow of combustion air to the
combustion zone in a direction and with such control as to
lead to greater heat being produced in combustion than has
hitherto been normal.
It is another object of the invention to provide a
closed stove with transparent door panels for visual
appreciation of the fire with improved characteristics with
regard to maintaining transparency against dirt, particularly
creosote.
It is another object of the invention to provide a
fire box with improved insulation characteristics over
previously known fire boxes whereby the heat of combustion ~
can be conveniently maintained therein.
It is another object of the invention to provide a
stove having an efficient heat exchanger to remove heat from
venting flue gases and transfer such heat into the room to be
heated.
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It is yet another object of the invention to
provide a framing assembly which allows positioning of the ~'
stove into an existing fireplace opening to make use of an i,
existing chimney without structural disturbance. It is a ~,
further object that the framing assembly allows positioning
of the stove within said fireplace opening with a versatile
degree of projection therefrom. Thus, although greater heat
radiation may be achieved by projecting the stove into the
room, if desired the front of it may be flush with the
chimney breast if the opening is deep enough.
Accordingly, the invention provides a stove for
location into a fireplace opening leading into a chimney,
said stove comprising:
a housing having a top, bottom, front, back and two
sides, said front comprising a fuel access aperture and
intake means for recirculating air comprising a foraminous
lower front marginal portion and outlet means for
recirculating air comprising at least a foraminous upper
front marginal portion;
a combustion unit within said housing comprising
two sides, a back, top, imperforate bottom and front, each
spaced from the housing sides, back, top, bottom and front
respectively, the spacing defining passage means for
recirculating air, the unit front comprising a fuel access
aperture and a front lip upstanding from said unit bottom and
extending between said unit sides; said front lip, said unit
bottom together with lower portions of said unit back and
sides defining a combustion trough;
support means for supporting the unit spaced on the
housing bottom;
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refractory lining means on said unit bottom;
exhaust means for exhausting flue gases from said
unit through said housing top;
passage means for flow of combustion air through a
lower portion of said housing front over said unit front lip
into said trough.
The invention also provides draft deflection means
to deflect any draft through points where doors adjoin each
other on the housing. The draft deflection means may
comprise a flange attached to one of a pair of adjoining
hinged doors at the top and bottom of said one door and
spaced from said one door over the height thereof, said
flange being provided over its length with portions angled
towards the closed position of said doors.
The invention also provides, as exhaust means, a
heat exchanger having a flue gas passage means from said
combustion unit top, through said housing top into said
chimney and recirculating gas passage means for at least part
of recirculating gas, and means for directing the flue gas
around the recirculating gas passage means.
The invention also provides a surrounding frame for
a stove to locate said stove in a fireplace opening and to
close any residual gap in said fireplace opening, said frame
comprising:
structural frame bars having means to fix them
together to fit tightly around the housing in a vertical
plane;
surrounding frame members fittable together to
surround the sides and top of said housing in a vertical
plane;
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tightening tneans to attach said surrounding members
to said structural frame members and to tighten the fitting
together of said surround members.
DESCRIPTION OF THE DRAWINGS
The drawings illustrate a stove having all the
improved features of the invention. It is, however, to be
understood that the heat exchanger, draft deflection, or
framing means independently provide improvements to any
suitable stove if fitted thereto.
IN THE DRAWINGS
Figure 1 is a perspective view, partly cut away, of
a stove according to the invention;
Figure 2 is a schematic section of combustion
trough of the stove of Figure 1 showing a combustion draft
passageway closed:
Figure 3 is a schematic section similar to Figure 2
but showing the combustion draft passageway open and
including the top parts of the housing and combustion unit;
Figure 4 is a schematic section similar to Figure 2
showing increased insulation of formed ash and charcoal;
Figure 5 is a perspective view, partly cut away, of
the exhaust means of the stove of Figure l;
Figure 6 is a diagram of draft deflection means
showing flow of draft behind a pair of stove doors,
Figure 7 is a schematic illustration of a framing
assembly for framing a stove for location into a fireplace
opening;
Figure 8 is a view from the rear of the assembled
frame of Figure 7;
Figures 9 and 10 are side views of a stove and
frame located in a fireplace opening.
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A stove according t~l the invention comprises a
housing 10 inside which and spaced therefrom is a combustion
unit 12. The housing 10 comprises a back 14, two sides 16, a
bottom 20, a top 22 and a front 24. The front 24 has
expanded metal marginal panels 26, 27 leading into clearance
space between housing 10 and combustion unit 12. Front 24 is
provided with doors 28 hinged to the housing at outer
vertical edges 30 and having handles 34. The inner edges 32
meet when the doors 28 are closed. Doors 28 are held in
their closed position by any conventional latching mechanism
operated through latching control knob 36. An edging baffle
43 runs round the clearance space and is directed rearwardly
into the combustion unit 12 at 45 to the housing top 22.
The baffle 43 helps to avoid smoke eddying forwardly against
the doors.
The combustion unit 12 comprises an imperforate
bottom 38, a back 40, a top 42, two sides 46 and a front
comprising a front lip 48. Exhaust means 49 are located
between the housing top 22 and combustion unit top 42 to
allow flue gases to vent from the combustion unit 12. The
front lip 48 and the lower parts of sides 46 and back 40 and
bottom 38 define a combustion trough in which fuel such as
wood is burnt. The bottom 38 is lined with refractory
material 50 such as fire brick. The back 40, sides 46 and
front lip 48 may be lined with heavy 12 gauge liners 44. The
combustion trough is a feature of the invention The
combustion unit bottom 38 is spaced from the housing bottom
20 and the combustion unit is supported on the housing bottom
20 by legs 45 formed by downward extensions of combustion
unit sides 46. No additional grate is used. Very high
combustion temperatures can be achieved using the described
combustion trough. During the combustion process, gases are
driven out of the wood at temperatures ranging between 200 F
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and 550 F. The gases ignite and visual burning occurs at
temperatures above said 550 F. In the combustion trough
described this latter range of temperatures is achieved
rapidly due to the fact that the trough is well insulated
with refractory material 50 on which the fuel burns directly.
Ashes and charcoal (generally indicated at 18) formed further
insulate the combustion zone thus minimizing conduction away
from the zone of heat necessary for efficient burning.
A draft of combustion air into such a trough is
provided by directional means to provide such a draft at that
point of the fire where it will be most efficient. This may
generally be taken as being the hottest point of the fire.
A controllable draft of combustion air is provided
by means of draft passage leading from its intake 54 on the
lower front of the housing upwardly and rearwardly to rise
above front lip 48 of combustion unit 12 and then downwardly
to open at outlet 56. By this means combustion draft is
directed downwardly into the combustion trough. A log
retainer 58 is located behind and mainly above front lip 48.
The draft passage comprises a lower passage 60 and an upper
passage 62 interconnected by a slot 64 between them. Passage
60 has a blind end 66 beyond the slot 64. Control of the
quantity of combustion draft is achieved by valve means
comprising wedge-shaped piston 74 carried on a movable rack
68. The rack 68 meshes with a pinion 70 which is operated by
a manual control knob 72. By sliding knob 72 in one
direction the piston 74 can be moved towards blind passage
end 66 (see Figure 2) where it does not obstruct the flow of
combustion draft. By moving the knob 72 in the other
direction the piston 74 can be moved in lower passage 60
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(see Figure 3) to partially or wholly obstruct slot 64 from
the combustion draft.
The housing front 24 includes a lower marginal
panel 26 of expanded metal located in front of bottom
clearance space between housing 10 and combustion unit 12.
Panel 26 defines an intake for recirculating air to be
heated. The housing fron-t 24 also includes another marginal
panel 27 which, in the illustrated embodiment, extends around
the front top and front side margins. Panel 27 defines an
outlet for heated recirculating air.
When a fire is lit in the combustion trough a draft
is created by the fire pulling combustion air in through
inlet 54, lower passage 60, slot 64, upper passage 64 and
outlet 62 under log retainer 58 provided that piston 66 does
not obstruct passage 60. This draft feeds the fire. Flue
gases vent through exhaust means 49. As the fire becomes hot
the refractory material 50 heats through and the whole of the
combustion unit heats up. Air present in the clearance space
is heated and rises between the housing back 14 and the
combustion unit back 40 thus drawing in cool air through
expanded metal panel 26. Warmed air vents into the
surrounding environment through expanded metal panel 27. The
main flow path for recirculating air is in through panel 26
under the combustion unit bottom 38, upward between unit back
40 and housing back 14.
There is also some inflow from panel 26 into the
space between each housing side 16 and the corresponding
combustion unit side 46. The flow path between the sides is
not so simple as around bottom 38, back 40 and top 42 but the
effect is to vent warmed air in varying degree over the
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height of the side front part of panel 27.
Where the recirculating warmed air passes between
the housing top 22 and the combustion unit top 42 it must
pass exhaust means 49 which vents flue gases from the unit
12. In order to provide as little impedance as possible to
the warmed air and to provide considerable extra heating
thereof exhaust means 49 is formed as a heat exchanger.
As can be seen in Figure 5 heat exchanging exhaust
is in the form of an open-ended shallow box having side walls
76, its ends opening through housing top 22 and unit top 42.
Flue gases can thus escape from unit 12 through the box whose
depth is substantially that of the space between the housing
top 22 and unit top 42. Pipes 78 are provided with their
length lying in the direction of flow of recirculating room
lS air. The ends 80 of the pipes project through opposing side
walls 76 of the exhaust means 49.
The ends 80 of the pipes are widened to seal joint
and encourage recirculating room air to flow therethrough.
The flue gases leaving the unit 12 flow round the pipes 78
and deliver up some of their heat thereto to further heat the
recirculating room air. To deflect the flue gases from a
straight,upward path to achieve greater contact with pipes
78, V-shaped baffles 82 are provided. Baffles 82 are located
parallel with pipes 78, each baffle lying between and above
adjacent pipes. At the box sides 76 parallel with pipes 78
and baffles 82 it is preferable that a baffle has adjacent a
side wall 76 rather than a pipe but this is not of great
importance. The entire box including side walls 76, pipes 78
and baffles 82 may be made from stainless steel.
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There is usually sonle clraft drawn into the housing
10 through the joins between the door edges 32, 30 and the
housing 10. Also, when a single door is used there may be
some leakage of draft into the housing around the edges.
Figure 6 illustrates two door panels of the invention each
comprising a pane of toughened glass 84 surrounded by heat
protective transparent screening 86. The door panels are
conveniently mounted in a door surround carrying the handles
34 as shown in Figure 1. However, Figure 6 illustrating
draft deflection means shows the door panels without such
surround. Inside the housing around the edges of the door or
doors particularly along vertical edges a flange 88 is
located. Flange 88 lies parallel to and behind the doors in
the closed position whereby any draft leaking into the
housing 10 through the join between door and housing 10 is
deflected across the rear surface of the door parallel
thereto.
Flange 88 may suitably be provided by means of an
L-section bar 90 having legs 92 and 88. Leg 92 is fixed to
20 the housing 10 to locate leg 88 parallel to closed door 28.
When there are two doors 25 joining at edges 32 further
deflection means comprise a flange 94 located behind the join
between doors 28 and generally parallel to the doors when
closed. Flange 94 has vertical margins 96 angled towards the
closed doors 28 but spaced therefrom. Flange 94 may be
carried by one of the doors 28 at the top and bottom. The
effect of flanges 88 and 94 is to direct any leakage draft
across the surface of the doors as shown by the arrows in
Figure 6. This has a cooling effect on the transparent door
panels and minimizes corrosion buildup thereon.
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~ccording to the invention is provided a framing
assembly for locating a stove into a fireplace opening
leading to an existing masonry chimney. One embodiment of
such a framing assembly shown in Figures 7 to 10 comprises a
U-shaped structural member 98 having a web 100 and legs 102.
A stove housing, such as housing 10 is located with its
bottom 20 resting on web 100 and the legs 102 extend up the
sides 16 of the housing. The actual position of the member
98 relative to the housing front 24 and housing back 14 is
partly a matter of choice. On one hand, the exhaust means 49
must be located behind the plane of member 98 so that flue
gases can vent therefrom up the chimney. On the other hand,
the greater the proportion of the housing 10 projecting
forward of the member 98 the greater the heat radiation into
the room. To some extent also the location of member 98 is
dependent on the depth of the fireplace opening into which
the housing 10 is to be set. Figure 9 shows a housing 10 in
a member 98 located in a shallow fireplace 104 and Figure 10
shows a similar housing 10 and member 98 set in a deeper
fireplace 106. In each case the member 98 is located
differently between the front and back of housing 10. It is
recommended that member 98 be set so that at least 1 to 2
inches of housing project from the fireplace opening. Having
chosen the position of member 98, a top structural member 108
which is fastened to top frame 114 and is bolted down thereon
with bolts 110 and nuts 112. The structural members are thus
fixed around the housing 10.
Thereafter side frame members 116 are located as
shown in Figure 8. Each member 114, 116 comprises a U-shaped
channel member mitred accurately to fit together with ,some
overlap at right angles to make a frame around the top and
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sides of housing 10. Trim, for example brass trim (not
shown) can be fitted around inner and/or outer edges of the
frame members 114, 116. When the frame members 114, 116 are
loosely assembled around the structural members 98, they may
be attached thereto by any suitable fixing means, for
example, bolts or screws (not shown).
The back of the frame members are then packed with
insulation material which may help to form a seal between the
fireplace and the frame members. The assembled housing 10
and frame is moved into its position in the fireplace opening
104 or 106. Levelling screws can be used under the housing
bottom. The frame members 114, 116 fit closely against the
front of the fireplace overlapping it by a varying amount
depending on the size of the fireplace opening.
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