Note: Descriptions are shown in the official language in which they were submitted.
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Description
FORCED AIR HEATING UNIT
Technical Field
The present invention relates generally to heating units and more specifi-
cally to a free standing heater using forced air.
Background Art
With the energy crisis a great concern, people have generally been
preoccupied with maximizing the use of cheap and inexpensive fuels. A major
effort has been made to include heat collectors in fireplaces to collect the heat
normally generated by the wood burning therein and to transmit it into the room
more efficiently than that provided by the normally designed fireplace. A forced
air system in combination with such heat collectors is shown in U.S. Patent
3,896,785.
Even before the energy crisis, people were concerned with the loss of heat
escaping through the flue of a heating source. Patents 1,490,135 and 3,09~,980
make use of the flue heat in a stove and fireplace respectively to heat a second
column of forced air which is introduced into the room in which the stove or
fireplace is located.
Prior art space heaters have also been used or converted to fireplaces to
provide a pleasing and second mode of heating. An example of this is shown in
Patent 1,944,626
Although showing many methods of recapture of heat loss by normal
fireplace or space heaters, the prior art has not made the most effective use of the
heatlng source. By concentrating their efforts on hotter fires or recapture of flue
gases, the prior art has not effectively captured the heat available from the
burning material. No effort is made to limit air flow to the fire and up the flue of
a fireplace or open fire box except in closed systems with small intake vents.
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Thus there exists a need for a system of limiting air flow into the fire box
and up the flue for open fireplaces or fire boxes.
Heating units of the prior art have either used the natural upward flow of
heating air by drawing cold air in at the bottom of a heating unit to exit heated
from the top. Also, forced air systems have been used to augment the naturPl
upward flow by moving more air past the extericr of the fire box. Although the
forced air systems have increased the capture of available heat, the prior art
devices have not optimized the heat transfer from the burning material in the fire
box to the air circulated about the exterior of the fire box.
The natural flow of drawing cold air in the bottom and exiting hot air from
the top or just exiting hot air from the top (naturally or forced) creates a hot layer
adjacent the top of the room and a cold layer at the floor. Thus there exists a need
for a heating unit which maximizes the capture of heat available in burning
material and which provides a more uniform temperature in the room.
The build-up of deposits on the exterior of the fire box in prior art devices
result from incomplete combustion of the gases from the burning material. These
deposits reduce the thermal convection of the heat in the fire box through the fire
box wall. Similarly, the loss of these gases up the flue is a loss of an available
source of combustion and additional heat.
Thus there exists a need for a fire box which increases heat and reduces
deposits.
Another problem with heating units of the prior art is the escape of smoke
and other gases drawn from the fire box by the pressure differential produced by
rapidly opening the doors of the fire box.
Disclosure of Invention
The present invention is a forced air heating unit having double walled sides,
back, and bottom, and a single walled front and top. A forced air channel, defined
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by the double sides, back and bottom wall, includes a system of baffles to direct
forced air over substantially all of the surface area of the side, back, and bottom
fire box walls. The baffles in the back portion of the forced air channel direct
forced air between the b~ck portion and the two side and bottom portions. The
baffles in the bottom portion direct forced air between the bottom portion and the
back and two side portions. The baffles in the side direct forced air between the
side portions and the back and bottom portions.
A blower is thermostatically controlled to introduce forced air into the air
channel for maintaining the back, side and bottom fire box walls in a minimum
temperature range to heat the forced air while maximi~ing the transfer of heat
from the burning material to the forced air channel instead of up the flue.
The front wall of the heating unit includes an access opening and a pair of
doors for covering the access opening. An adjustable draft valve in each door
includes a positive screw lock. Depending from the top of the fire box adjacent the
flue port in the rear of the fire box is a gas baffle for directing rising gas to an
area of the fire box where the gases are ignited. The gas baffle directs some of
the gas downward to the burning material to be ignited and maintains some of the
gases adjacent the top of the fire box in front of the gas baffle. The top of the
doors are spaced from the top edge of the access opening to allow air to circulate
into the firebox adjacent the top wall for aiding ignition of the gases collected
adjacent the top wall. The major source of air is the space between the doors
which is covered by a vertical strip mounted to one of the doors. A hood is
mounted adjacent the top edge of the access opening for directing gases exiting the
top edge of the access opening back into the fire box.
Por an open fireplace or fire box, a draft system, including two vertical
forced air channel exit vents adjacent the side edges of the access opening for
creating hot air drafts which converge at a selecteed distance in front of the
~ocess opening, limits the draft Or eir into the access opening. The converging hot
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air is effected by vertical deflection surfaces including
vertical baffles in the side portion of the forced air channel
or pneumatic surfaces produced by a lip extending across the
vent opening or by the vent opening being offset from the ex-
terior edge of the forced air channel. The less than ninety
degree angle that the side walls form with the front of the
forced air channel also aids the deflection. A mesh having
inclined horizontal surfaces covers the vertical vents and dir-
ects the exiting air downward to be combined with heated forced
air exiting horizontal vent in the front of the bottom portion
of the forced air channel~ The heated forced air from the two
vertical vents and the horizontal vent pneumatically create a
finite cool air pocket in front of the access opening to limit
the amount of cool air available for the fire box.
The forced air heating unit uniformly heats a room by
introducing forced hot air adjacent the floor of the room by
the horizontal vent and the downward directing vertical vents.
The forced air device mounted to the rear of the free-standing
unit draws air from above and around the sides of the unit and
around the space defined by the exiting forced hot air. The
width of the side portion of the forced air channel tapers from
the wider rear portion to the front to increase the air intake.
Gravity lock door handles are provided on the access doors.
Broadly stated, the invention relates to a forced air
heating unit comprising: a chamber for holding a source of heat,
an opening in the front wall of said chamber for providing
access' a flue orifice in said chamber for removing fumes, a
forced air channel surrounding a back wall, side walls and a
bottom wall of said chamber, said channel including substan-
tially the entire back wall, said two side walls and said bottomwall of said chamber, the back portion of said forced air channel
communicates with the two side and bottom portions of said
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forced air channel and said bottom portion communicates with
said two side portions; vertical vent means in the front wall of
said side air channels adjacent each side of said opening and
horizontal vent means in the front wall of said bottom air
channel, blower means for forceably introducing air through
an inlet means into said back portion of said air channel and
over substantially the entire surface of said back wall of
said chamber, baffle means interior said back, two side and
bottom portions of said channel for directing forced air from
said back portion to said two side portions and over substan-
tially the entire side walls and from said back portion to
said bottom portion and over substantially the entire bottom
wall and from the bottom portion to said side portions, said
forced air emitting from said heating units through said hori-
zontal and vertical vent means.
Brief Description of Drawings
Figure 1 is a front perspective view of a forced air
heating unit employing the principles of the present invention.
Figure 2 is a partial cross-sectional view of the
draft valve taken along lines II-II of Figure 1.
Figure 3 is an exploded, partial perspective view of
the relationship of the top of the doors to the fire box open-
ing.
Figure 4 is a partial side view illustrating the
function of the hood according to the present invention.
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Figure 5 is a rear cutaway perspective of the forced air heating unit illus-
trating the baffle system.
Figure 6 is a front partial perspective of the bottom, back, and side walls of
the forced air heating unit illustrating the baffle system.
Figure 7 is a perspective schematic of the heat flow in the fire box.
Figure 8 is a side cross-sectional view illustrating gas circulation in the fire
box.
Figure 9 is a front perspective of a fireplace employing the principles of the
present invention.
Figure 10 is a side view illustrating the forced air pattern according to the
principles of the present invention.
Figure 11 is a plan vjew illustrating the forced air pattern according to the
principles of the present invention.
Figure 12 is an enlarged plan view of a vertical vent illustrating the deflect-
ing principle of the present invention.
Figures 13 and 14 are enlarged plan cross-sectional view of alternative
embodiments of vertical deflectors.
~ igure 15 is a front view of the mesh used in the vents.
FIgure 16 is a cross-sectional view taken along lines XVI-XVI of Figure 15.
Figure 17 is a schematic of the air circulation produced by the present
invention.
Figure 18 is a front view of another embodiment of the principles of the
present invention.
17igure 19 is a perspective of another embodiment of the present invention.
Best Mode for Carrying out the Invention
~ igure 1~ which illustrates a preferred embodiment of the forced air heating
unit 10, shows a housing having top, front, bottom, two sides, and back walls, 12,14,
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16, 18, 20, and 22 respectively. Top wall 12, which is a single walled portion of the
housing, extends past the front, back, and side walls, and includes a collar 24 sur-
rounding an orifice or flue port 26. A flue (not shown) to remove the fumes from a
source of heat or combustible material is connected to flue port 26 through the
collar 24. The heating unit 10 is supported by four legs 28 providing space betweeen
the floor and the bottom wall 16. Front wall 14 has Q pair of elongated vertical
vents 30 and 32, each covered by a screen 31 which is secured to the front wall 14
by a bracket or lip 33.
An access opening 34 in front wall 14 is covered by a closure including a pair
of doors 36 and 38. The vertical vents 30, 32 extend substantially the height of the
opening 34 and are spaced from the bottom and top of the opening 34. The door 38
has a strip 40 which overlaps door 36 and holds door 36 closed and covers the space
between the adjacent edges of the doors. Handle 42 on door 38 is connected to a
latch 43 which engages the top interior portion above the opening 34 so as to lock
the doors closed. The handle 42 rotates down to close, thus providing a gravity lock
of the doors. A pair of posts 41 and 45 on the interior of the doors 38 provides tops
for latch 43. Post 41 may be mounted to the interior of front wall 14 if desired.
Also provided on doors 36 and 38 are a pair of draft valves 44 and 46. The
sliding portions 50 and 52 of draft valves 44 and 46 slide within guide members 54
and 56 to adjust the size of a plurality of elongated openings 48 in doors 36 and 38.
When a fire is provided in the interior chamber of housing 10, the slides 50 and 52
ad~ustably vary the draft valves 44 and 46 to regulate the amount of air or draft
introduced into the chamber and are locked in the adjusted position by threaded
knobs 51 and 53 respectively engaging the face of doors 36 and 38 respectively as
illustrated in Pigure 2. For a wood burning source of combustible material, this
wo~d vary the rate of burning as well as the temperature. These valves are used in
conjunction with an adjustable flue port 26. Although the draft valves 44, 46 are
shown in the doors 36, 38, they may ~lso be used on a front wall of the fire box
below the doors if such a surface is made available. The doors 36 and 38 are
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mounted to the housing by upper hinges 58 and 60 and lower hinges 62 and 64, re-
spectively. The doors and hinges are dimensional so that the bottom of doors 36, 38
rest flush against the front wall 14 and the top of doors 36, 38 are spaced from the
front wall 14 at the top edge of opening 34 as illustrated in Figures 5 and 19. The
importance of this separation will be discussed below in reference to Figures 3 and
8.
Also mounted to the front wall 14 is a hood 66 and a platform 68. The hood
66 traps any smoke pulled from the fire box at the upper edge of access opening 34
when the doors 36, 38 are rapidly opened and directs it back into the fire box as
illustrated in Figure 4. The hood 66 includes a center portion 65 and a pair of side
portions 67 for capturing the escaping gases and directing them back into the
opening 34. The platform 68 provides a surface for supporting a fireplace screen
when the heating unit 10 is used as a fireplace without doors.
The forced air system includes a source of forced air, a channel, a baffle
system, and deflectors. The source of forced air, including a housing 70, is
mounted to the back wa 22 and includes an opening 72. Located within the
housing 70 is a blower 71 or any other system which will receive air through opening
72 and provides a forced air flow within the channels to be described. A
thermostatic control 73 is mounted in rear wall 22 (l~igure 6) and controls the
operation of fan 71 based on the temperature of the air in the forced air channel.
Housing 70 may also contain a source of moisture which is illustrated in Figure 5,
~or example, as a pan 74 having water therein. The pan of water is merely one
example of a source of moisture. Forced air housing 70 communicates with the
forced air channels via an inlet 76 in the back wall 22.
~ lthough the location of inlet 76 and blower 71 on the back wall is preferred
for most applications, they may be located any place which provides them access to
the forced air channel. For example, inlet 76 and blower 71 could be on either side
wall 18, 20 or on top 12 over the back or either side portion of the forced air
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channel. Similarly, they may be on the front wall 14 with access to the two side or
bottom portion of the forced air channel.
The air channel of the present device includes the exterior sides, back, and
bottom walls 18, 20, 22, and 16 respectively and interior sides, back, and bottom
walls 78, 80, 82, and 84 respectively. The sides and back walls of the housing and
the sides and back interior walls form a generally U-shaped forced air channel with
the side walls at an angle other than ninety degrees relative to the back where the
forced air from opening 76 is transmitted towards front vents 30 and 32. The
separation of the side walls 18 and 78 and 20 and 80 or the width of the side forced
air channel tapers or diminishes from the rear to the front. The increased width of
the back air channel and the rear of the side air channel allows blower 71 to pump
more air per minute into the forced air channel. The forc~d air from opening 76 is
also provided from the rear forced air channel through an opening 86 into the
forced air channel formed by the housing and the interior bottom walls to exit
through horizontal vent 88, illustrated in Figure 6, in the front portion of the
bottom air channel. The air in the bottom forced air channel also exits into the
side forced air channels. Thus it can be seen that forced air traverses substantially
the total surface of the interior back, side, and bottom walls.
Within the forced air channels are bafne systems to create specific air
patterns which diverge from the forced air source at opening 76 and converge on
the respective vents in the front of the air channels. The rear wall portions of the
bafne system includes a horizontal baffle 90 substantially bisecting opening 76
from the forced air system. Also provided in the rear wall are two upper baffles 92
and 94 and two lower baffles 96 and 98 which diverge from the forced air opening
76. Baffles 94 and 96 direct divergent air flow towards one side wall channel while
baffle 92 and 96 in combination direct diverging air flow toward the other side wall
channel. Upper baffles 92 and 94 direct an upward flow towards the respective side
wall channel portions and baffles 96 and 98 provide a flow towards opening 86 into
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g
the bottom forced air channel as well as providing a small flow to the respective
side forced air channel.
Located in each side forced air channel are baffles 102,104,106, and 108, and
in bottom forced air channel are baffles 112,1~4,116,118,120,122, and 124. The inner
ends of bottom baffles 114,116,118~ and 120,122,124 are offset relative to the center
bottom baffle 112 so as to divert varying portions of the air flowing towards bottom
vent 88 and to direct it towards side wall baffles 102 and 104. The angle and
location of baffles 114,116,118,120,122 and 124 are such that the air between baffles
114-116 and 120-122 is directed toward the lower face of side baffle 102; and the air
between baffles 116 and 122 and the rear of the bottom is bisected by baffles 118
and 124 respectively and directed between baffles 102 and 104. Since the source of
the temperature modification is generally placed adjacent interior bottom wall 84,
the communication of the air flow from the bottom forced air channel to the side
forced air channel increases the efficiency of the temperature transfer.
The specific design of the baffles and their location assures that the air
traverses substantially all the interior walls and thereby allows a greater heat
transfer from the interior or fire box to the forced air without sacrificing the head
of the air emitting from the vents 30, 32, and 8~ since it cools a greater surface
area. Prior art devices generally substantially increase the length of the air path
while sacrificing the head of the air at the vents and thereby reducing the heat
transferability of the interior walls. The baffle system in the walls produce
streams of air which are not troubled by eddy currents, dead air pockets, localized
hot spots, and other disadvantageous features of the prior art systems.
Blower 71 is chosen to have sufficient capacity to force air in the air channel
at a sufficiently high velocity to lower the temperature of the interior walls and
thereby increase the transfer of heat from the fire box to the interior walls to be
removed by the forced air. Thus less heat from the fire box is available for
trarlsmission up the flue. ~or a heating unit eighteen inches high without legs by
twenty-three inches wide at the front by fourteen inches deep, a blower having a
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capability of pumping 140 cubic feet of air per minute is sufficient. A blower
pushing 465 cubic feet per minute is adequate for a unit twenty-seven inches high
by forty-two inches wide by twenty inches deep.
An analysis of the thermodynamics of the heating unit 10 will substantiate
the efficiency or maximization of heat transfer or capture of the unit. The
formula for representing the heat transferred from the heated air in the fire box
through the interior walls to the forced air in the forced air channel is:
Q = A U ~T
where Q= heat transferred in BUT/hour;
A= effective heat-transfer surface area perpendicular to the direction of
heat flow in feet square;
1~ T= mean temperature difference between the forced air and the fire box
air in degrees fahrenheit;
11= overall heat-transfer coefficient in BTU/(hour)(feet)2 (F)
The overall heat transfer coefficient Q is a function of the resistance to the flow
of heat of (a) the air in the fire box, (b) the firebox wall, (c) the forced air, and (d)
the fo~ing on each side of the fire box wall.
One way to maximize the transfer of heat is to create as great as possible
temperate differential T. The blower 71 in combination with thermostat control
73 maintain the back, two sides, and bottom wall of the fire box in a range of
temperature to maximize the heat transfer through the fire box walls while heating
the forced air to a sufficiently warm temperature. For example, thermostat 73
co~dd turn blower 71 on once the temperature in the forced air channel is 115 F. and
turn the blower 71 off when the forced air temperature is reduced below 100 F. If
desired, the thermostat control 73 co~d vary the speed of blower 71. The preferred
range is 95 P. to 150 F.
By forcing air over substantially all the back, two sides, and bottom fire box
walls, heating unit 10 substantially maximizes the effective surface area A at the
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greatest temperature differential. This area could be further increased by
extending the forced air channel over the top wall 12 of the fire box, if desired, but
is not preferred.
The heat flow within the fire box is also based on the above equation except
that the temperature differential ~ T should be expressed as a temperature
gradient or the change in temperature per unit distance. The amount of heat flow
is illustrated in Figure 7 by the length of the vector. Since the bottom forced air
channel, being the closest cool surface, has the largest gradient or vector D. The
forced air cooled two side and back walls, being substantially equidistant from the
fire, have the next largest vectors L,R, and B, respectively. The front wall, being a
non-forced air wall, can only cool by heat dissipation. Thus, the temperature
gradient toward the front wall, and consequently the heat flow P, is substantially
less than those toward the forced air cooled walls. Similar to the front waU, the
top wall is not forced air cool and thus has a small heat flow U. Since gas ignition
occurs adjacent the top (as will be discussed for Figure 8), the surface of the top
wall is even hotter than the front wall and consequently vector U is smaller than
vector E~. With a limited air flow up the flue, there is very little heat left to exit
the nue port as illustrated by vector 0.
Thus the thermostatically controlled blower maximizes the surface area of
maximum temperature differential to effectively capture or draw eighty percent of
the heat available from the fire box into the forced air channel. This is comparable
to the heat efficiency of a residential furnace.
To maximize the heat transfer coefficient of the unit 10, a device is
provided to reduce the build-up of deposits on the fire box wall by igniting the
rlslng gases from a wood fire. This ignition also increases the amount of heat
available from the wood. This device includes a gas baffle 126 extending down from
the top wall 126 adjacent the flue port 2~ as illustrated in Figure 8.
With the doors 36, 38, closed, the slide drafts 44, 46 on the doors allow a
controlled, even flow of air across the fire. As the wood is burned, the unburned
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gases rise from the fire up and slightly forward, to the top wall 12. As they contact
the top wall 12, they circulate to the rear of the fire box, toward the flue port 26
and contact baffle 120 which deflects the gases downward. At this point, some will
go under the baffle 126 and out the flue port 26, some will be pulled back into the
fire and reburned, and some will be recirculated at the top 12 by the gases rising
from the fire.
Approximately 30 seconds after an even fire has been established, A rolling
cushion of smoke (partially burned gases) will build up under the top wall 12. This
cushion acts to hold the resins and gases in the fire to burn longer and holds the
gases in the fire box until they are recirculated and burned as completely as
possible.
As the wood gases rise away from the fire, they cool quite rapidly. In order
to prevent the cooling gases from liquefying and building up creosote deposits
inside the fire box, and later in the chimney, a small amount of secondary air is
injected at the top of the doors 36, 38. The secondary air injection ignites the
gases directly under top wall 12. This secondary burning action more completely
burns the gases and raises the temperature of the smoke escaping up the chimney
sufficiently to prevent the solids in the smoke from separating and building up
inside the chimney. This action also raises the temperature of the top wall 12 to
cooking level.
The space between the two doors 36 and 38 and the mounting of the doors 36
and 38 so that the top edges of the doors are spaced from the top edge of the
access opening 34 permits the secondary air flow into the area adjacent the top
wall 12 aiding the ignition of gas collected there. Although the air space is
provlded by the tops of the doors being offset from the plane of the front wall 14,
this space may also be provided by making the top of the doors shorter than the
access opening 34.
The forced air heating unit 10, as illustrated in ~igure 9 may be used as a
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free standing fireplace. The doors 36 and 38 are removed and a screen 128 is
provided underneath hood 66 and resting on platform 68. The screen may be a
typical fireplace screen to prevent sparks and ashes from emitting from the
fireplace and causing a fire hazard within the room. Adjacent to and surrounding
openings 34 is a rim 130. Four pins 132 of hinges 58, 60, 62, 64 are provided on the
rim 130 as well as four openings 134 in the rim. The matching hinge element of the
closures 36, 38 move in and out of the openings 134 in the rim 130. In addition to
providing the pin portion 132 of the hinges for the closures 36 and 38, the rim 130
provides a guide and retainer for the screen 128 which fits within the rim 130.
Though not shown, the rim 130 extends above and across the top of the opening 34.
A pair of andirons 136 are provided in the interior chamber to support the source of
temperature modification. It should be noted that grating or other supports may
be used instead of andirons 136.
The forced air heating device 10 includes a system of deflectors at the
vertical vents 30 and 32 to define a unique air flow pattern in front of the fire box
opening 34. As illustrated in Figures 10 and 11, the heated forced air (dashed lines)
from vertical vents 30, 32 are directed towards each other to converge in front of
the fire box opening 34 a preselected distance. This creates an air pocket 140 in
front of the fire box opening 34 in combination with the heated forced air exiting
the bottom horizontal vent 88 which is illustrated in Figure 10 but deleted from the
pattern of Figure 11 for sake of clarity. The pneumatically created barrier for air
pocket 140 limits the amount of air from which the fire can draw and thereby
reduce~ the rate of combustion in the fire box. Also, the outward moving heated
air reduces cold air drafts toward the access opening 34. The U-shaped pneumatic
barrier is a critical substitute for the open or removed doors 36 and 38.
The major source of cool air (solid lines) for the pocket 140 in front of the
fire box is the triangular aerodynamic openings 142 between the bottom of the
vertical vents 30, 32 and the forced air from the horizontal vent 88. The forced
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hot air from vertical vents 30, 32 also is directed downward, as well as inward to
converge, allowing air to flow into the pocket 140 over the top edge of the freed
hot air V. The two vertical air streams converge preferably at about five feet in
front of the access opening. To converge much closer would draw smoke from the
fire box.
Blower 71 on the back wall draws air as indicated by the solid lines around
the sides of the unit and over the top. Thus the cool or return air flow is outside
the air pattern defined by vents 30, 32 and 88 which pneumatically block cool air
flow into the fire box.
A preferred device for directing the air exiting the vertical vents 30 and 32
to converge is illustrated in the enlarged view of Figure 12. The side walls 18 and
78 are mounted to the front wall 14 at an opening 144 in the front wall. While side
wall 78 lies at the edge of the opening 144, side wall 18 is slightly offset. This
offset may be eliminated. The side walls 18, 78 form an angle less than ninety
degrees with the front wall 14 to aid the deflection of forced air inward. The
brs¢ket 33 i6 generally L-shaped having a portion extending across the opening 144.
The bracket 33 forms an air pocket along the outside edge of opening 144 which is a
pneumatically produced deflection surface 146. The pneumatic deflection surface
exterior the forced air channel is sufficient to direct the heated forced air to
converge in front of the fire box access opening 34.
Two alternative embodiments are illustrated in Figures 13 and 14. In lieu of
the external pneumatic deflector 146, an internal pneumatic deflector could be
wed. As shown in Figure 13, the exterior side wall 18 is substantially offset from
the edge of opening 144 providing a pneumatically produced deflection surface 148.
~igure 14 shows a vertical deflection plate or baffle 150 mounted between the
exterior side wall 18 and front wall 14. The side forced air channels form a ninety
degree angle with the front wall, although the non-ninety degree sngle alignment is
preferred. Each embodiment may also include the pneumatical deflection surface
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136 produced by the L-shaped bracket 33.
The downward air flow is produced by the mesh 31 secured to the L-shaped
bracket 33 across vent opening 144. As i~ustrated in Figures 15 and 16, the mesh 31
includes a plurality of horizontal surfaces 152, at the intersection of adjacent
openings, inclined downward from the back to the front to deflect air downward
without retarding the air flow through the mesh 31. If the downward deflection is
not required, mesh 31 may be mounted with the surfaees 152 vertical to provide the
converging air flow. Basically, the mesh 31 may be mounted with any desired
orientation of the surfaces 152 to produce a correspondingly directed air flow (e.g.
45 angle relative to the horizontal).
The forced hot air patterns converging just off the floor in front of the unit
push the cool air across the floor. When the forced air strikes a wall, it is
deflected to either side and up. At the same time, the blower 71 is pulling return
air to either side and down over the top of the unit. This push-pull action res~ts in
a high volume of air movement as the blower system forces hot air across the floor
and returns cool air around either side and overhead. This is exactly the opposite
of normal air movement within a house and results in a more uniform temperature
from floor to ceiling. The air patterns are illustrated in Figure 17 where the solid
lines represent cool air and the dashed lines represent warm air.
A thermostat 154 may be provided in the room to be heated. Whereas
thermostat control 73 preferably turns the blower on and off as a function of the
air temperature in the forced air channel, thermostat 154 varies the speed of the
blower as a function of the air temperature in the room to be heated. The use of a
room thermostat increases the comfort in the room, but reduces the efficiency of
the unit 10 since the fire box walls may not be kept at the lowest possible
temperature.
Although the vertical units 30 and 32 are preferred so that the heating unit
10 could be used as a fireplace or operated with the doors open, they may be
eliminated. The flow pattern of Figure 17 may also be produced by using only vents
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in the front of the bottom forced air channel. As illustrated in
Figure 18, two additional vents, one size 6 and one size 8 are
provided on each side of vent 88. The pushing of warm air
adjacent the fIoor and pulling cool air from above, evenly heats
the room.
The heating unit 10 could also be used as a furnace.
As illustrated in Figure 19, top vent 160 and 162 may be con-
nected to the plentum or duct systems to betransmitted throughout
a house. In either of these two embodiments, the baffle system
is modified so as to direct air over substantially all the
surfaces and towards the vents without forming dead air pockets-
in the forced air channel.
Although reference has been toward fires, the heating
unit 10 is effective for use with coal, oil, gas, or any other
heat source in the fire box.
Preferred method of assembly of a forced air heating
unit 10 is to form the exterior side and back walIs 18, 20, and 22
out of a single piece of material and the interior side and back
walls 78, 80, and 82 also out of a single piece of material.
The baffles are mounted to the exterior side and back walls and
the interior side and back walls are mounted to the baffles pref-
erably by welding. The bottom exterior wall 16 is welded to the
exterior side and back walls 18, 20, 22, and the baffles of the
bottom forced air channel are mounted to the bottom exterior`wall.
The bottom interior wall 84 is then joined to interior side and
back walls 78, 80, 82. The top and front walls are then mounted
to the structure by welding. The welding bead formed between the
top and the side and back walls provides a thermal barrier or
guard such that the portions of the top 12 which extends beyond
the side and back walls is cooler than a portion of the top which
is directly over the fire box. The remaining elements are attach-
ed or mounted to the front wall and the forced air unit mounted
1115611
- 16a -
to the rear wall.
It is suggested that the interior side and back walls
78, 80, and 82 be made of 3/16" thick steel and the exterior
side and back walls as well as the top and front walls be made
of 1/8" thick steel. The botto~ exterior and interior walls
may be made of 3/16" steel. The selection of different thicknesses
of steel
1~15Ei11
provides for a maximum absorption of the heat of the interior chamber as a heat
exchanger to be used in contact with the forced air which cools the interior walls
while taking advantage economically of thinner exterior walls.
From the preceding description of the preferred embodiments, it is evident
that the objects of the invention are obtained. A forced air heating unit is
provided which maximizes the use of available heat from a fire box by a unique
thermostatically controlled forced air system including pneumatically produced
surfaces and barriers. Although the invention has been described and illustrated in
detail, it is to be cleQrly understood that the same is by way of illustration and
example only and is not to be taken by way of limitation. The spirit and scope of
this invention is to be limited only by the terms of the appended claims.
