Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This invention is concerned with radiant heater
stoves, particularly wood-burning stoves. The invention is
more especially concerned with a viewing door for a wood-
burning stove, with an improved stove door and with an
improved stove construction.
Conventional wood-burning stoves include a front
opening through which wood logs for burning can be intro-
duced into the stove. The front opening is closed by means
of ~ metal door, usually of cast iron which has a relatively
air-tight fit in the front opening~
Air must enter the stove to provide efficient
burning of the wood; the air suitably enters the stove
through an opening in the metal door, the opening being
controlled by a valve whereby the flow of air into the ~ -
stove can be regulated, as desired.
It is also conventional to employ a mesh screen
which is disposed in front of the ~tove opening, when the
metal door is opened, so that the burning wood can be
viewed, as in a conventional open fireplace.
~his may be particularly desirable when the wood
stove is used in a family room or den of the home or cottage.
The stove thus has two operating modes, a first
in which the stove door is closed, hnd a second in which
the door is open and a viewing screen is disposed in front
of the stove opening.
The operation of the stove and its requirements
are, however, quite different for the two modes. In parti-
cular the flue and chimney requirements are quite different
for the two modes.
In the second mode a large amount of air enters the
stove, without control, through the front opening and burning
of the wood proceeds far more rapidly, operation in this
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second mode requires a large diameter chimney for removal of
large amounts of smoXe and gases generated by the rapidly
burning wood.
In the first mode the wood burns more slowly,
and efficient operation is favoured by a small diameter
chimney. A small diameter chimney ensures that smo~e and
gases of combustion, conveying combustion products pass
from the stove and through the chimney at a higher velocity
than would be the case for a large diameter chimney; this
ensures that products of combustion such as creosote are
conveyed through the chimney, with the gases, before they
condensate within the flue and chimney.
In the first mode of operation the slow efficient
burning, or lower rate of burning, produces a smaller
amount of smoke and combustion gases which, as generated,
do not have a sufficiently high velocity to efficiently
transport combustion products such as creosote, a small
diameter chimney generates a high velocity in the com-
bustion gases.
Thus the chimney requirements ~or the two modes
of operation are opposite to each other. In practice the
stove design is dictated by the second mode of operation,
and a large diameter chimney is provided to ensure that
smo~e and combustion gases do not exit the stove through
the ~ront opening into the room where the stove is installed,
or create such high flue velocities that the temperature
in the chimney becomes excessive. This oversized chimney
condition in the first mode adds to the installation cost
and the combustion products such as creosote are not
efficiently conveyed from the stove and collect in the
chimney, thereby deleteriously affecting the safety and
necessitating regular cleaning of the chimney to avoid
chimney fires.
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In response to this problem wood-burning stoves
have been developed which include a glass screen or window,
which fits air-tightly into the front opening to cut down
excess air drawn into the stove, and through which the
burning wood can be viewed in the second mode of operation.
In addition to its aesthetic value the glass
screen has the advantages that it provides visual feedback
when regulating the inflow of air into the stove and the
damper controls, and e~ables the user to monitor the
supply of wood in the stove without having to continually
open and close the stove door.
On the other hand such glass screens represent
a hazard unless special high temperature performance ~lass,
which can withstand mechanical impact and elevated
kemperatures for prolonged periods, is employed.
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One special high temperature performance glass
which has been used for glass screen~ or windows in wood-
burning stoves is a 96% silica glass available from Corning
Glass Works, Corning, New York, U.S.A., under the trade
mark "Vycor"~ This glass has good thermal durability
and at 0.25 ins. thickness can be used safely at
temperatures as high as 1652F. and has a maximum
temperature of thermal shock of 1800F.
The Vycor glass is, however, expensive, it is
available from a single supplier and is only available in
certain cut sizes, which means t~at the stove design,
particularly the dimensions of the front opening are
dictated and limited by the available sizes of the glass.
A further disadvantage of Vycor is that it is
a rolled glass and is not completely clear, but provides
a hazy viewing window and has a lower impact mechanicl
resistance than tempered glass.
The most widely available glass is soda lime glass
which comprises 9~/O of all glass manufactured. This glass
is available from a wide variety of suppliers and can be cut
and dlmensioned as desired by the purchaser. Soda lime glass
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is formed by floating the molten glass over a lake of
molten tin and has a mirror quality smooth surface, and is
completely clear. Soda lime glass can be tempered to four
times its normal annealed strength and is the logical choice
in applications with operating temperatures less than 400F.
At temperatures above 400F., tempered glass
loses its temper with time and may shatter. Consequently,
the use of tempered glass in wood-burning stoves, when
operating temperatures are higher than 400F. is not
appropriate.
It is also conventional in stove design to employ
a stove door which is cast`from iron. Cast iron doors are
employed because they do not warp or buckle at the high
temperatures developed in wood-burning stoves. Manufacture
of cast iron doors, however, requires particular equip-
ment and skills and necessitates that many stove manufacturers
have stove doors manufactured on their behalf by companies
skllled in casting.
It would be simpler and less costly for stove
manufacturers not having f~cilities for the casting, to
f~bricate a steel door employing metal forming and welding
techniques, unfortunately steel doors are subject to warp-
ing and buckling at the elevated temperatures developed in
wood-burning stoves.
The present invention provides solutions to these
difficulties in wood-burning stoves.
In one aspect of the invention there is provided a
viewing door for a radiant heating stove comprising a door
frama, an inner gLass panel and an outer glass panel, mounted
in opposed, spaced apart relationship in said frame, a passage
for flow of air currents, clefined between said panels, door
mounting means on said door to mount the door in an opening
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of a stove, such that said outer panel is spaced apart
from said opening, said glass panels being of tempered
glass which loses its temper, with time, on exposure to
operating temperatures in excess of 400F.
The glass panels are suitably of air tempered
soda lime glass having a maximum temperature of
thermal shock of 400F., and are float-formed, that is they
are formed by floating the molten glass on a molten metal
whereby a clear, non-hazy glass having a smooth surface
is formed.
Air tempered glass is glass that has been rapidly
cooled or chilled from near its softening point under
rigorous control to increase its mechanical strength and
maximum resistance to thermal shock.
During the rapid cooling the inner portion of the
glass continues to contract as it cools, after the outer
surface of the glass has been locked in place by the rapid
chill, The result is that the outer s~lrface is put into
compression while the inner portion is tensioned. When
a glass plate is deformed, most of the load is carried
on the outer surface and bending causes the outer surface
to tension. It is the additional compressive force in
the outer layer that must be overcome that gives tempered
glass more strength than normal annealed glass, it is also
this stored up energy that may cause tempsred glass to
fragment or fly apart when broken. If a tempered glass is
heated beyond its recommended operating temperature, it
will begin to give up its temper.
In another aspect of the invention there is pro~ided
a stove door compxising an integrally formed ~uter metal box
panel ana an integrally formed inner metal box panel, said
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inner box panel being mounted within said outer box panel,
said outer box panel having an inside wall spaced apart
from an inside wall of said inner box panel to define an
air cavity between said box panels, an air-inlet in said
outer box panel, for flow of air into said cavity, an air-
outlet in said inner box panel for flow of air out of said
cavity, said air-outlet being remote from said air-inlet
such that air-flowing through said cavity flows across
said inside walls.
The integrally formed box panels are suitably
formed as steel casings welded together along a seam
defined between the contacting portions of the casings to
define the air cavity therebetween; the air flowing across
the facing inside walls of the casings cools them and
prevents warping or buckling of the steel casings which
would otherwise occur on exposure to temperatures
developed iII the stove. At the same time the flowing air,
which cools the walls of the casings,is itself heated and
this heated air can be directed into the stove, whereby
the burning efficiently is enhanced.
There is also provided in another aspect of the
invention a wood-burning stove having mounted therein one
or both of a viewing door and a stove door of the invention.
In yet another aspect of tha invention there is ,
provided in a wood-burning stove, comprising: a stove housing
containing a fire-box,a front opening in said housing for
introducing wood into the fire-box, and a chimney for exit
of smoke and products of com~ustion from the stove; the
improvement comprising an air passage d~fined between the
fire-box and a bottom wall of the housing and between the
fire-~ox and a rear wall of the housing, said air passage
being continuous from end to end, and including an air-blower
adapted to blow hot air in said air passage over said bottom
wall away from said rear wall. Air convexion up with blower
turned off - residual cooling.
In this way hot air is delivered forwardly of
the stove to a lower part of a room in which the stove is
located, whereby the heated air is efficiently employed
in the heating of the room.
When the air blower is turned off, the heated
air in the air passage passes upwardly over the rear wall
so that cooling of the room is achieved more rapidly.
The air passage also functions to form a
radiation shield, the rear wall of the housing being
maintained at a lower temperature than the rear wall of
the fire box. As a result the stove can be located with
only a relatively small clearance between the stove rear
wall and the interior wall of the building adjacent which
the stove is to be located.
The invention is illustrated in particular and
` preferred embodiments by xeference to the accompanying
drawings in which:
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FIGURE 1 is a perspective view of a stove with
the stove doors open and a viewing
door of the invention mounted in
position,
FIGURE 2 is a side view in cross-section of the
stove of Figure l;
FIGURE 3 is a perspective view of the stove of
of Figure 1 with the stove doors and
viewing door removed;
FIGURE 4 is a perspective vi~ew of the viewing
door mounted on the stove in Figure l;
FIGURE 5 is a plan view of t'he viewing door
of Eiguxe 4
FIGURE 6 is a schematic side view of a viewing
door on a stove;
FIGURE 7 is atop plan, paxtially cut away of the
viewing door of Figure 4,
FIGURE 8 is a perspective view of an upper
mounting element for the outer frame
of the viewing door of Figure 4;
FIGURE 9 is a perspective view of ~ lower
mountiny element for the outer frame of
~ viewing doox of Figure 4;
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FIGURE 10 is a view of a portion of a viewing
door in a dif-Eerent embodiment, in
w~li.ch the air orifices are adjust-
able,
FIGURE 11 is a front perspective view of a stove
door of the invention,
FIGURE 12 is a rear view of the stove door of
Figure 11,
FIGURE 13 is a plan view o~ the stove door of
Figure 11,
FIGUR~ 14 is an exploded view of the stove door
of Figure 11;
FIGURE 15 illustrates graphically the loss
of temper, with time, of a tempered
qoda lime glass exposed to an :
elevated temperatur~, and
FIGURE 16 illustrates graphically the lowering
of the maximum temperature of thermal
shock of tempered soda lime glass, ~ ~
with time, on exposure to an elevated ~ ~:
temperature.
With furth~r reference to Figures 1, 2 and 3, a
stove 10 comprisas a stove housing 12, on legs 25, and
including a stove top 14, a stove bottom 16, side walls 18
and 20, a rear wall 22 and a front wall 24.
A pair of stove doors 26, are shown in the open
position, in Figure 1, the stove doors 26 are hingedly
mounted on front wall 24 at hinges 27, which include hinge
elements 29 on front wall 24.
An ash apron extends forwardly of front wall 24 and
a flue collar 30 for mounting a chimney extends from stove to
14.
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A front opening 32 is defined in front wall 24,
wit~ a door rim 23 in the opening 32. A viewing door 34 is
mounted in door rim 23.
The stove housing 12 contains a :Eire box 90
including a fire box rear wall 91 and a fire box bottom
wall 92~
A continuous air passage 94 is defined between
walls 91 and 92 of fire box 90 and rear wall 22 and stove
bottom 16 of the stove housing 12.
Air passage 94 includes a horizontal passage
96 having an outlet 97 and a vertical passage 98 having
an outlet 99. An air blower 100 is mounted at the base
of vertical passage 98.
With :Eurther reference to Figures 4 to 9, viewing
door 34 comprises a door frame 36 incl.uding an inner ~rame
member 38 and an outer frame member 40, an inner glass
panel 42 is mounted in frame member 3~ and an outer glass
panel 44 is mounted in frame meniber 40. A flame resistant
gauze 46 is mounted in frame member 38, inwardly of glass
panel 42.
Frame member 38 includes an upper wall 48, a
lower wall 50 and end walls 52 and 54.
Outer frame merriber 40 is mounted on inner frame
men~er 38 ~y upper mounting elements 56a and 56b and lower .
mounting elements 64a and 64b.
An air passage 72 is defined between inner glass
panel 42 and outer glass panel 44.
A row of spaced apart air orifices 74 extend
through upper:wall 48, and a similar row of air orifices 76
extend through lower wall 50. The air orifices 74 and 76
are located inwardly of gauze 46.
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Flanges 78 extend outwardly from inner edges o~
frame member 38 including ~langes 78a and 78b extending
from upper wall 48 and lower wall 50 respectively, and
flanges 78c and 78d extending from end walls 52 and 54
respectively.
A pair of handles 80, include handle mounts 82
mounted on end walls 52 and 54 respectively, and handle
holds 84.
Door mounting brackets 86 and 88 are mounted on
10 end walls 52 and 54 respectively. .
Door bracket 86 includes a lateral portion 86a ~-
and a bent over :Lip 86b. Bracket 88 similarly includes
a lateral portion 88a and a bent over lip 88b.
Mounting element 56a, shown in detail in Figure 8,
includes an angular body 57 including a side wall 59a
secured to end wall 52 and a top wall 61a secured to
upper wall 48; an L-shaped front retaining wall 60a extends
from wall 59a and an L-shaped rear retaini.ng wall 63a extends
from wall 61a, defining a slot 58a therebetween.
M~unting ~lement 56b secured to end wall 54
and upper wall 48 is a mirror image of element 56a and has
like parts designated by the same number but with a letter
"b" instead of a letter "a"~ ; -
Mounting element 64a, shown in detail in Figure
9, includes an angular body 63, including a side wall 65a
secured to end wall 52 and a bottom wall 67a secured to
lower wall 50, an L-shaped rear retaining wall 68a extends
from wall 65a and an L-shaped front retaining wall 70a
extends from wall 67a, defining a slot 66a therebetween,
Mounting element 64b, secured to end wall 54 ~ :
and lower wall 50 is a mirror image of element 64a and has
like parts designated by the same number but with a letter ;,
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"b" instead of a letter "a".
Outer frame member 40 is contained between
upper slots 58a and 58b and lower slots 66a and 66b.
Inn~r frame member 38 includes upper
and lower lips 49 and 51
extending towards each other from the front edges of walls
48 and 50 respectively, and side lips 53 and 55 extending
towards each other from end walls 52 and 54 respectively.
Gauæe supports 73 and 75 mounted on the inside surface of
end walls 52 and 54 include lips 77 and 79 spaced apart
from and generally parallel to side lips 53 and 55
respectively to define slots 81 and 83 therebetween.
Glass panel 42 is resiliently retained in
slots 81 and 83 with resilient cushioning material 102.
Gauze 46 is mounted in frame member 38 with its
side edges clamped between gauze supports 73 and 75 and
the inside surface of end walls 52 and 54 respectively.
Outer frame member 40 includes a continuous
slot 85, glass panel 44 being resiliently retained in
slot 85 with resilient cushioning material 104.
The resilient cushioning material or gasket
material 102 and 104 is suitably a felt or paper of high
tem~erature, thermally resistant fibres, for example,
ceramic fibres, particularly silica-alumina fibres, and
serves to cushion the glass panels against mechanical
shock, while at the same time allowing for thermal expansion
of the glass and metal parts. By way of example suitable
felt or paper materials include those available under the
trade marks 'KAOWOQL" and "FIBERFRAX",
With further reference to Figure 10, there is
shown a portion of an inner frame memher 38 of a viewing
door 34, An elongated plate 140 is slidably mounted on the
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underside of upper wall 48. A row of air orifices 14~
corresponding to and adapted to register with orifices 74,
pass through plate 140. A narrow slot 144 is defined in :
upper wall 48 and a handle 146 is mounted on plate 140
through slot 144.
With further reference to Figures 11 to 14, a
stove door 26 includes a door handle 106, an air adjuster
108 and door hinge elements 110.
Stove door 26 is composed of an outer box panel
112 welded to an inner box panel 114 along a continuous
seam defined by an outer edge 138 of box panel 114.
A continuous recess 116 is defined between the outer
edga of box panel 114 and the inner edge of box panel 112.
A fire-resistant gasket 118 is contained within recess 116.
Air adjuster 108 includes an air control
member 120 rotatably mounted on a spindle.122. An adjust-
able air gap 124 is defined between air control member 120
and front surface 126 of box panel 112.
Air-inflow apertures 128 are disposed in front
surface 126 behind air control member 1~0.
A plurality of air-outflow apertures 130 is defined
in imler box panel 114, and an a:ir cavity 132 is defined
between the substantially flat inner surface 134 of box
panel 112 and the substantially flat inner surface 136 of
box panel 114. Inner suraces 134 and 136 are disposed in
a substantially parallel spaced apart relationship.
The door hinge elements 110 are hingedly mounted
on hinge elements ~9 on front wall 24 of stove 10 and
together form hinges 27, Air adjuster 108 may suitably
be formed as a weldment rather than as a casting.
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In the first mode o operation of the stove the
stove doors 26 close the front opening 32 in stove 10, the
viewing door 34, shown in Figure 1, having been removed.
In this mode the front opening 3~ is substantially air-
tightly sealed by the doors 26.
A flow of air necessary for combustion of wood
which is burning in the fire box 90 of the stove 10, is
maintained by means o~ air adjuster 108.
Air control member 120 is rotatable on spindle
122 from a closed position in which there is no air gap
124 and the air-inflow apertures 128 are closed by air
control member 120, to open positions with varying air
gaps 124. When the air control member 120 is rotated to
an open position in which there is an air gap 124, air is
drawn throu~h air-inflow apertures 128 into the air cavity
132 and then through air-outflow apertures 130 and into
the fire box 90. The amount of air is regulatable by
adjustment of the air control member 120 to vary the air
gap 124.
The air cavity 132 extends over substantially the
whole of the facing surfaces 134 and 136 of the box panels
112 and 114. The aix-outflow apertures 130 are disposed
remotely from air-inflow apertures 128 such that the air
passing through air cavity 132 flows across a major part of
the surfaces 134 and 136 and cools them. In this way the
box panels 112 and 114 are air-cooled, and even though they
are exposed to the elevated temperatures generated in the
fire box 90, the temperatuxe of the doors 26 does not rise
too significantly to cause distortion. By maintaining the
doors 26 air-cooled in this manner, it is possible to fabri-
cate the door from steel which normally warps or buckles on
exposure to elevated temperatures.
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In particular the box panels 112 and 114 are
formed from steel and are welded together along a continuous
seam formed between outer edge 138 of box panel 114 and
the contacting portion of inner surface 134 of box panel
112, whereby costly casting techniques requiring particular
skills can be avoided.
The air passing through cavity 132 is itself
heated as it cools the door 26, so that preheated air is
delivered through apertures 130 to fire box 90. The use
o~ preheated air, in this way, improves the burning
efficiency in the stove 10.
The fire resistant gasket 118 serves to air-
tightly seal the doors 26 in the front opening 32, whereby
the delivery of air into fire box 90 can be accurately
controlled by adjustment of air control member 120. The
gasket is suitably of a rope of high temperature, thermally
resistant fibers, particularly ceramic fibers, for example,
the ceramic fiber rope available under the trade mark
"Fiberfrax".
In the second mode of operation the doors 26 are
opened, as shown in Figure 1, and can, i~ desired, be
removed. The viewing door 34 is temporarily mounted in
front opening 32 by means of brackets 86 and 88 which clip
over the hinges 27 of the stove doors 26. More parti-
cularly the lateral portions 86a and 88a of brackets 86
and 88, are supported on the upper side o~ the upper hinge
elements 29 on front wall 24, and the bent over lips 86b
and 88b extend vertically downwardly behind the hinge
elements 29 to hold the viewing door 34 securely in position.
When viewing door 34 is mounted in position the
flanges 78 sealingly engage the door rim 23 to provide a
suhstantially air-tight seal.
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Air for combustion of the burning wood in this
second mode, enters the fire bo~ through air orifices 74
and 76, the cross-sectional area of the ori~ices 74 and 76
being suitably determined by the cross-sectional area o~
the chimney (not shown) to be disposed in flue collar 30.
In the fire box 90 there is both primary and
secondary burning, primary burning involving the burning
of the wood and secondary burning involving the burning
of the gases produced. It is found that the orifices 74
in the upper wall 48 have a greater afect on the efficiency
of burning in the fire box, it is believed that the supply
of air from the upper orifices 74 more significantly affects
the secondary burniny in the fire box 90.
Therefore it is appropriate to have adequate air
entering the fire box 90 from the orifices 74. If orifices
74 are closed and the air enters only from the lower orifices
76, the efficiency of the burning diminishes and this i5
believed to be due to a diminishment of the air supply to
the gases above the burning wood, and thus a diminishment of
complete combustion in the secondary burning. On the other
hand closing orifices 76 does not produce such a decrease in
burning efficiency, pro~ided sufficient air is fed through
orifices 74 to meet the fire box requirements, It would seem
that most of the air ~ntering lower orifices 76 is utilized by
the burning wood, any excess air speeding up the wood~
burning primary process, whereas the air entering upper
orifices 74 is able to reach the upper regions of the fire
bo~ 90 and is utilized in both the primary and secondary
processes.
In accordance with the embodiment illustrated in
Figure 10, the open area of the orifices 74 can be diminished
by sliding plate 140 along the underside of upper wall 48,
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by moving handle 146 along slot 144. In this way the
orifices 142 move out of register with orifices 74, and
the plate 140 will block orifices 74 to an amount depending
on the extent of movement of plate 140.
During the second mode inner glass panel 42 is
protected from flames from the burning wood by the gauze
46, since a flame will not pass through gauze 46~
The gauze 46 is suitably of expanded metal mesh
having openings sufficient to enable viewing of the burning
wood through glass panels 42 and 44.
The metal gauze 46 also protects glass panel 42
from the development of hot spots, which would produce
localized, unbalanced internal stresses in the glass.
The rows of air orifices 74 and 76 are disposed
inwardly of gauze 46 rather than between gauze 46 and the
glass panel 42, to avoid the possibility of flame devalop-
ment at the air orifices, which flames would contact the
glass panel 42.
Glass panels 42 and 44 are of tempered glass
~hich loses its temper, with time, at temperatures above
400F. The rate of loss of temper with time depends on
the temperatures in excess of 400F. to which the glass is ~ -
exposed.
The flow,of air through passage 72 between the
glass panels 42 and 44, illustrated in Figure 6, provides
a cooling effect, to cool the glass panels 42 and 44, and
particularly the outer glass panel 44O In this way the outer ~
glass panel 44 can be maintained at temperatures significantl~ ~ -
below 400F. even though the temperature developed in the
fire box is significantly higher than 400F. The inner glass
panel 42 is also cooled, although the temperature is generally
higher than that of the outer glass panel 44. If the inner
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glass panel 42 eventually fails, after a prolonged period
of exposure to elevated temperatures, as a xesult of loss
of temper, and shatters, the outer glass panel ~4 acts as
a safety glass and prevents the fragments of glass from
the shattered panel 42 from flying from the stove. When
this arises a new inner glass panel 42 can be readily
installed for further operation.
By means of the present invention the chimney
cross-section can be selected for efficient burning during
hoth the first and second modes of operation of the stove,
the burning wood can be safely viewed employing the
temporary viewing door without loss of the burning
efficiency, and a tempered glass can be employed, which
permits a clearer view of the burning wood, without haziness,
while at the same time being more versatile in that the
tempered glass panels 42 and 44 can be readily obtained,
cut to any desired dimension.
With further reference to Figure 2, in the
operation of stove 10, air in air passage 94 becomes heated.
Since hot air rises, the hot air tends to be drawn along
horizontal passage 96 towards vertical passage 98 and then
upwardly through vertical passage 98, whereby hot air is
delivered upwardly from the rear of the stove lO through
outlet 9g. In the stove 10 of the invention, blower 100
blows the hot air in passage 94 along horizontal passage 36
and through outlet 97 forwardly of the stove 10~ In this
way the hot air is directed fcrwardly of the stove into a
lower part of the room, and then rises upwardly to heat
the room, thereby providing a more efficient utilization
of the heat developed by the stove. When the hot air is
delivered through outlet 99 as in conventional stoves, the
heat delivered to an upper portion of the room, is inefficiently
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employed being lost to most of the room.
It will be evident that various modifications
of the stove 10 can be employed, within the invention. In
particular although the viewing door 34 is preferably
included as an accessory to be temporarily mounted in the
front opening 32 of stove 10, the viewing door 34 may be
permanently mounted in the front opening 32, with a
separate access to the stove interior, for introducing
wood being provided, for example, in the stove top 14.
The viewing door 34 might also be hingedly
mounted on one side of front opening 32, whereby front
opening 32 could be employed for access to the stove
interior, by opening viewing door 34 about its hinge
mounting. In this case only one handle 80 would be required.
The viewing door 34 illustrated in Figure 4
includes a single pair of door mounting brackets 86 and 88
adapted to be mounted on the upper door hinges 27. It will
be evident that door 34 could additionally include a
second pair of door mounting brackets, similar to 86 and
88, for mounting on the lower door hinges 27.
The embodiment in Figure 10 shows an air ori~ice
adjusting plate 140 on the underside of upper wall 48 of
frame member 38. It will be recognized that plate 140 could
also be located on the underside of lower wall 50, in the
same manner, or that plates 140 could be located under
upper wall 48 and lower wall 50.
The plate 140 may provide an infinite variation
in the orifice opening, or locking stopg can be provided
in slot 144 to temporarily lock plate 140 at predetermined
positions, in which, for example, the air orifices /4 or
76 are 10~/o~ 75%, 5~/O~ 25% and ~/O closed.
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The stove 10 may have a single stove door 26
hingedly mounted at one side of the front wall 24, and
extending over front opening 32, or it may have a pair
of stove doors 26, as shown in Figure 1. In the case in
which a single stove door 26 is employed, this may
suitably have two spaced apart air adjusters 108.
As shown in the drawings the passage 72 between
the glass panels 42 and 44 is open on four sides~ This
is not essential, however, and the passage need only be
open an amount sufficient to induce or allow adequate
convection of air between panels 42 and 44, to cool the
panels, particularly panel 44.
The handle holds 84 are suitably of a material
which does not retain heat, for example, wood, or as
illustrated in the drawing a coil of metal wire. In this
way the viewing door 34 can be readily removed after use
even though the ~rame 36 may be hot.
EXAMPLE
.
A viewing door as shown in Figures 4 to 9 was
assembled for a stove 10 as shown in Figure 1, having a
6 inch diameter flue~ Upper wall and lower walls 48iand
50 of frama member 38 each had a row of 12 spaced apart
air orifices 74 and 76, each air orifice having a dia-
meter o~ 0.25 inches.
The glass panels 42 and 44 were spaced about 1
inch apart, measured between their facing sur~aces. The
panels were of float-~ormed,tempered soda lime glass. The
tempered glass had the characteristics set for~h in Table
I below, which also shows the characteristics of the soda
glass before tempering and the characteristics of the ~ -
silica glass available under the trade mark VYCOR.
Oil r~
I~l-rl U~ O O O U~ ~
C O O O .~ C
~4 a) a) ~ 1 C 1~
~!)
O ~ C
~ ~ l . ~ ~ ru
~J ~ C ~ I~ I ~) h
O O I I O
oU h-~ ~1 o o Iq Q, a~
~1 ~1
C ~I rC C X ~1 (D ~
H (U E~ ~a X ~C
\ a) p~ ~ ~ u~
~ o u X . ~ ~ ~ ~n
H ~ ) O ~ d' U~ ll ) ~ ~rl O
~ ,C
a~
a~
U
.Y a
U '~
~ C ~D 0 ~ O R
X h ~D - ~, 0 ~ ia rC
a u ~ c
' O ~ ~
3 `
U ,C u~
O
~ O
X
O O O
s~ u o o
~ O co
4 ~ ~ ,-1
E~ u~ a~ (r
H ~ O n5
C -1
. ~ e a~ ~ ~ h
~ a~ (D U rl ~> O
~; 5-1 ~ rl 1~1 ~`1 O IQ ~1 .
E~ ~ ~ ~ D ~ ~ e ~
X s~ r~ ~ CO
Ji~ (U (~1 u a) n5
u~ X
~ ~ ~ r~
O
O ~
e u ~ a) 3 Q, ,a ~ .
~ ) o ~ 5-1 Ei U n5
O ~ IS) ~ t~ ~ r5 u~ rl
~ ~ t~l ,y ~ u~ ~ oq a
(I) r-l ~ 5 >
¦ ~1 u l a~ rC E~
o I ~I Q~ t:5) (U Q, Q)
Q 1~1~D rC
$ o a) -,1 ~ rl rC ~
rl ~ E-l rl
~> a) .
a~ u~
u~ a)
, e
~lU o x
.,, ~ ~
r~
rl q~ ~
U~ o o X
,X $~ a~ ~ g
u u~ ~ ~
~rl ~-1 a- e ~ e ~ -5 u~
n5 ~rl ~ ~ ~
E-l rl ~ n5 1~ r-l
_ h ~ (~ e ~ 5~ ~ ~
~5 ~ ~0 E~ ~g
,~ ~, u~ v~
El E~
The effec-t of elevated temperatures on the temper
and maximum temperature of thermal shock of the tempered
soda lime glass is shown in Figures 15 and 16.
With reference to Figure 15 it will be seen that
the temper decreases uniformly with time, on exposure to
an elevated temperature of 700F. Reference to Figure 16
shows that the maximum temperature of Thermal Shock also
decreases uniformly with time, on exposure to an elevated
temperature of 700F.
The viewing door was subject to tests designed
by the Underwriters Laboratory of Canada (ULC), as
standards for Solid Fuel Fixed Space Heaters. These tests
required that the outer ~lass panel 44 not exceed a
temperature of 400F. in the Brand Test, and not exceed
a temperature of 500F. in the Flash Fire Test. The viewing
door passed both tests; and the temperature of the outer
glas~ panel ~4 did not exceed 300F. The viewing door
also passed the Wet Cloth Test of ULC for thermal shock
resistance and the steel ball test for mechanical impact.
In general it is found that the outer glass
panel 44 typically had a temperature of at least 100 to
200F. lower than the temperature in the inner glass panel
42.
In the manufacture of the stove in accordance
with the invention the rim 23 in the front opening 32 of
stove 10 is suitably produced as a formed edge from front
wall 24, rather than being an added facing material.
The rim 23 could also be a facing material.
- 23 -
- ~
It should also be noted that the area of the
air orifices 74 and 76 in viewing door 34 is suitably
selected to maintain the flue temperature in a safe range,
having regard to the cross-sectional area of the chimney.
If the area of the orifices is too high with respect to
the cross-sectional area of the chimney the velocity of
exit of gases in the chimney, and the temperature in the
chimney may reach dangerously high levels.
It is to be understood that references to "air- -
tight'l sealing in this application are not intended to be
construed as identifying an absolute air-tight seal,
rather the component parts are designed to form a relatively
air-tight seal. For example, rim 23 in front opening 32
and the flanges 78 have substantially flat contacting
surfaces, whereby the flanges 78 èngage rim 23 to form a
substantially air-tight seal, of cours,e, there may be some
clearances for entry of air within the limits of the
mechanical tolerances used in fabricating the parts.
_ 24 -
