CA1125607A - Viewing door for radiant heater, and stove door - Google Patents
Viewing door for radiant heater, and stove doorInfo
- Publication number
- CA1125607A CA1125607A CA349,789A CA349789A CA1125607A CA 1125607 A CA1125607 A CA 1125607A CA 349789 A CA349789 A CA 349789A CA 1125607 A CA1125607 A CA 1125607A
- Authority
- CA
- Canada
- Prior art keywords
- stove
- door
- air
- glass
- wood
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F24—HEATING; RANGES; VENTILATING
- F24B—DOMESTIC STOVES OR RANGES FOR SOLID FUELS; IMPLEMENTS FOR USE IN CONNECTION WITH STOVES OR RANGES
- F24B13/00—Details solely applicable to stoves or ranges burning solid fuels
- F24B13/004—Doors specially adapted for stoves or ranges
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Combustion & Propulsion (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Special Wing (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
An improved viewing door for a radiant heating fire, particularly a wood-burning stove employs spaced apart panels of tempered glass, which loses its temper on exposure to operating temperatures in excess of 400°F. as normally experienced in a wood stove; an outer glass panel is spaced outwardly of the stove and is cooled by air currents drawn through the space, whereby the outer panel is maintained at a lower temperature and the temper is not lost; the tempered glass is a float-formed glass and is less costly, more widely available, can be obtained cut to order, and provides a clear non-hazy viewing window as compared with the more expensive, high temperature performance, rolled, silica glass which provides a hazy viewing window in the door and has a lower impact mechanical resistance than tempered glass.
There is also provided an improved stove door which is fabric-ated from a metal such as steel without casting; the problem of warpage on exposure to elevated stove temperatures is avoided by the provision of a cavity within inner and outer walls of the door, through which air flows; the flowing air cools the door and the thus heated air is directed into the stove and improves the efficiency. An improved stove is also provided which includes a continuous passage extending between the bottom and rear walls of the stove housing and the fire box, heated air in the passage is directed along the horizontal portion of the passage, forwardly of the stove and produces a radiation shield for the bottom and the rear of the stove to allow for reduced clearances to the back of the stove.
An improved viewing door for a radiant heating fire, particularly a wood-burning stove employs spaced apart panels of tempered glass, which loses its temper on exposure to operating temperatures in excess of 400°F. as normally experienced in a wood stove; an outer glass panel is spaced outwardly of the stove and is cooled by air currents drawn through the space, whereby the outer panel is maintained at a lower temperature and the temper is not lost; the tempered glass is a float-formed glass and is less costly, more widely available, can be obtained cut to order, and provides a clear non-hazy viewing window as compared with the more expensive, high temperature performance, rolled, silica glass which provides a hazy viewing window in the door and has a lower impact mechanical resistance than tempered glass.
There is also provided an improved stove door which is fabric-ated from a metal such as steel without casting; the problem of warpage on exposure to elevated stove temperatures is avoided by the provision of a cavity within inner and outer walls of the door, through which air flows; the flowing air cools the door and the thus heated air is directed into the stove and improves the efficiency. An improved stove is also provided which includes a continuous passage extending between the bottom and rear walls of the stove housing and the fire box, heated air in the passage is directed along the horizontal portion of the passage, forwardly of the stove and produces a radiation shield for the bottom and the rear of the stove to allow for reduced clearances to the back of the stove.
Description
ii~7 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.
~5~17 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 - -` ~2S~7 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 ~L~i~t7 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;
_ g _ i6~7 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.
-10_ 7' 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 ;, - 12 _ 5i6~7 "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 ~2~
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.
9~ lL2S6~97 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.
_ 16 _ 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, - 17 _ %~
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 , , 6~'7 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 _ 19 _ 2S6~
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
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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.
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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.
- ~
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 -
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 - :
~25i~
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.
~12~i6~
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.
~5~17 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 - -` ~2S~7 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 .:
~gL2~
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 ~L~i~t7 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:
~ 9L2~i66:1~
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;
_ g _ i6~7 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.
-10_ 7' 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.
. .
~2~ii6~7~
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 ;, - 12 _ 5i6~7 "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 ~2~
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.
~l~Z56i~,~
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.
9~ lL2S6~97 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.
_ 16 _ 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, - 17 _ %~
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 , , 6~'7 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 _ 19 _ 2S6~
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.
~5~
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 . ~ 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.
- ~
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 -
Claims (16)
1. A readily removable viewing door for a radiant heating stove comprising:
a door frame, 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, defined between said panels, door mounting means on said door to mount the door in an opening of a stove, such that said outer panel is spaced apart from said opening and said passage is open to the atmosphere, said glass panels being of tempered glass which loses its temper, with time, on exposure to operating temperatures in excess of 400°F.
a door frame, 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, defined between said panels, door mounting means on said door to mount the door in an opening of a stove, such that said outer panel is spaced apart from said opening and said passage is open to the atmosphere, said glass panels being of tempered glass which loses its temper, with time, on exposure to operating temperatures in excess of 400°F.
2. A viewing door according to claim 1, wherein said tempered glass is a float-formed, air tempered soda lime glass.
3. A viewing door according to claim 2, wherein said glass has a maximum temperature of thermal shock of about 400°F.
4. A viewing door according to claim 2, wherein said frame includes air inlet means therein to permit flow of air inwardly of the inner glass panel.
5. A viewing door accoxding to claim 4, including a fire resistant gauze mounted in said frame, inwardly of and in spaced relationship with said inner glass panel, said air inlet means being defined inwardly of said gauze.
6. A viewing door for a wood stove comprising:
a door frame including an inner frame member and an outer frame member, with a passage for flow of air currents between said frame members, said inner frame member including opposed upper and lower walls and opposed side walls, said upper and lower walls having orifices defined therein for passage of air into the stove, flange members extending from an inner end of each of said side walls and upper and lower walls, said flange members being adapted to sealingly engage the perimeter of a viewing opening in the wood stove, a first glass panel mounted in said inner frame between said walls, and outwardly of said orifices, a second glass panel mounted in said outer frame member, said first and second panels being in opposed, spaced apart relationship with said passage for flow of air currents extending between said panels, a flame resistant gauze mounted in said inner frame, inwardly of said first glass panel and outwardly of said orifices, said gauze extending between said walls and being effective to prevent travel of a flame there-through, said gauze comprising openings such that the interior of the stove can be viewed therethrough, door mounting means on said frame to temporarily mount the door on said viewing opening perimeter of the stove, at said flange members, said glass panels being of tempered clear glass having a maximum temperature of thermal shock of not more than 400°F., and characterized in that it loses its temper with time, on exposure to operating temperatures in excess of 400°F.
a door frame including an inner frame member and an outer frame member, with a passage for flow of air currents between said frame members, said inner frame member including opposed upper and lower walls and opposed side walls, said upper and lower walls having orifices defined therein for passage of air into the stove, flange members extending from an inner end of each of said side walls and upper and lower walls, said flange members being adapted to sealingly engage the perimeter of a viewing opening in the wood stove, a first glass panel mounted in said inner frame between said walls, and outwardly of said orifices, a second glass panel mounted in said outer frame member, said first and second panels being in opposed, spaced apart relationship with said passage for flow of air currents extending between said panels, a flame resistant gauze mounted in said inner frame, inwardly of said first glass panel and outwardly of said orifices, said gauze extending between said walls and being effective to prevent travel of a flame there-through, said gauze comprising openings such that the interior of the stove can be viewed therethrough, door mounting means on said frame to temporarily mount the door on said viewing opening perimeter of the stove, at said flange members, said glass panels being of tempered clear glass having a maximum temperature of thermal shock of not more than 400°F., and characterized in that it loses its temper with time, on exposure to operating temperatures in excess of 400°F.
7. A viewing door according to claim 6, wherein said tempered glass is a float-formed, air tempered soda lime glass.
8. A viewing door according to claim 7, wherein said glass panels are resiliently mounted in said inner and outer frames to avoid mechanical overstressing of the glass panels and accommodate thermal expansion.
9. A wood burning stove comprising a stove housing containing a fire box, an opening in the housing for introducing wood into the fire box, a chimney for exit of smoke and products of combustion from the stove, and at least one stove door adapted to air-tightly seal said opening and including a viewing door adapted to be temporarily mounted in said opening, when said at least one stove door is open, and being readily removable from said opening, said viewing door comprising a door frame, 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, defined between said panels, door mounting means on said door to mount the door in said opening of the stove, such that said outer panel is spaced apart from said opening and said passage is open to the atmosphere, said glass panels being of tempered glass which loses its temper, with time, on exposure to operating temperatures in excess of 400°F.
10. A wood-burning stove according to claim 9, wherein said opening is disposed in a front of the stove and said door frame is adapted to air-tightly seal said opening.
11. A wood-burning stove according to claim 10, wherein said tempered glass is a float-formed, air tempered soda lime glass.
12. A wood-burning stove according to claim 11, wherein said frame includes an air inlet means therein to permit flow of air into the fire box of the stove.
13. A wood-burning stove according to claim 12, further including a fire resistant gauze mounted in said frame, inwardly of and in spaced apart relationship with said inner glass panel, said air inlet means being defined inwardly of said gauze.
14. A wood-burning stove comprising a stove housing containing a fire box, an opening in the housing for intro-ducing wood into the fire box, a chimney for exit of smoke and products of combustion from the stove, and at least one stove door adapted to air-tightly seal said opening, and a viewing door, as defined in claim 6, adapted to be temporarily mounted in said opening, when said at least one stove door is open.
15. A wood-burning stove according to claim 14, wherein said opening is disposed in a front of the stove and said door frame is adapted to air-tightly seal said opening,
16. A wood-burning stove according to claim 14 or 15, wherein said tempered glass is a float-formed, air tempered soda lime glass.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA349,789A CA1125607A (en) | 1980-04-14 | 1980-04-14 | Viewing door for radiant heater, and stove door |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA349,789A CA1125607A (en) | 1980-04-14 | 1980-04-14 | Viewing door for radiant heater, and stove door |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1125607A true CA1125607A (en) | 1982-06-15 |
Family
ID=4116701
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA349,789A Expired CA1125607A (en) | 1980-04-14 | 1980-04-14 | Viewing door for radiant heater, and stove door |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1125607A (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2564183A1 (en) * | 1984-05-11 | 1985-11-15 | Labattu Michel | Closure system intended to be fitted to the front of a closed oven |
| US4638788A (en) * | 1983-01-17 | 1987-01-27 | Eurofours | Device for mounting a glass pane on an oven door |
| US6848441B2 (en) * | 2002-07-19 | 2005-02-01 | Hon Technology Inc. | Apparatus and method for cooling a surface of a fireplace |
| US7422011B2 (en) | 2005-02-22 | 2008-09-09 | Hni Technologies, Inc. | Fireplace front panel assembly for reducing temperature |
-
1980
- 1980-04-14 CA CA349,789A patent/CA1125607A/en not_active Expired
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4638788A (en) * | 1983-01-17 | 1987-01-27 | Eurofours | Device for mounting a glass pane on an oven door |
| FR2564183A1 (en) * | 1984-05-11 | 1985-11-15 | Labattu Michel | Closure system intended to be fitted to the front of a closed oven |
| US6848441B2 (en) * | 2002-07-19 | 2005-02-01 | Hon Technology Inc. | Apparatus and method for cooling a surface of a fireplace |
| US7422011B2 (en) | 2005-02-22 | 2008-09-09 | Hni Technologies, Inc. | Fireplace front panel assembly for reducing temperature |
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