Note: Descriptions are shown in the official language in which they were submitted.
CA 02552492 2006-12-08
HEAT ACTIVATED AIR SHUTTER FOR FIREPLACE
FIELD OF THE INVENTION
The present invention relates generally to fireplaces and similar devices.
In particular, the present invention relates to an apparatus for a fireplace
unit or
the like that regulates primary airflow to a burner of a fireplace. More
particularly,
the present invention includes an air shutter assembly automatically
responsive
to heat for controlling airflow to a main burner and/or a secondary burner to
a gas
fireplace or similar heating/lighting unit.
BACKGROUND OF THE INVENTION
Fireplaces are desirable features in the home. However, devices that
1s burn non-solid materials, such as gas, or that produce heat electrically
have
gradually replaced traditional wood or other solid fuel-burning fireplaces.
Like,
wood, the combustion of gas does provide real flames and heat, but requires a
careful mixing of gas and air for optimal performance and a realistic flame.
This
aspect of the gas fireplace, and similar appliances, typically involves the
delivery
of air for combustion to an arrangement or device where the air is mixed with
gaseous fuel, e.g., natural gas and propane ("gas"). Clearly, it is
advantageous
that the air and gas are mixed at a ratio for proper combustion. Then, the
mixed
air and gas are delivered to a burner, and ultimately provided to a combustion
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chamber of the fireplace. In some instances, the mixing of air and gas is
accomplished in the actual burner itself.
Multiple such arrangements have been created that are passive in nature,
such as manifolds of a given size and shape with orifices designed to deliver
a
fixed ratio of air and gas for combustion. This ratio is typically optimized
at a
steady state, heated operating condition. It is well known that steady state
operation of a gas fireplace typicaliy takes 30 minutes or more. Some
manifolds,
ducts, inlet passages, air passages and the like are routed through the
fireplace
to preheat the combustion air and increase the efficiency of the fireplace.
One
io example of such a device is illustrated in U.S. Patent No, 6,295,981.
As a fireplace or similar type of unit transitions from a cold start to a
steady state of combustion it has been observed that the change in efficiency
of
the combustion and increase in heat causes an change in the properties of the
is flames produced. Namely, the flames tend to be blue at the onset of
combustion
when the unit components and intake gases are at room temperature. The
flames gradually transition to a more desirable yellow color as combustion
becomes more complete. Since the air/gas ratio of the unit is typically preset
for
correct burning at a heated, steady state condition in conventional gas
fireplace
20 units; a unit may operate under less than ideal combustion conditions at an
initial
cold start condition creating a condition for a long initial period of time
where very
little yellow flame is observable.
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This start up conditioti, i.e., with the unit generating a predominantly blue
flame, can cause disadvantages, both in a sales environment, where it is
desirable to demonstrate a fireplace with yellow flames to a potential buyer
and
installed where the unit takes a relatively long period of time to reach a
condition
where the flames have an aesthetically pleasing appearance. The first
disadvantage occurs where a salesperson wishes to demonstrate an attractive
appearing fireplace without the cost of keeping fireplaces in a steady state,
heated condition. The second problem is related to consumer satisfaction of a
pleasant appearing fireplace without the long wait for the unit to develop to
a
ro steady state condition.
Whereas many gas/air mixing schemes are simply designed and set for a
steady state condition, i.e., at operating temperature at equilibrium, some
fireplaces provide a mechanism for adjusting the air/gas mixture. However, if
improperly adjusted or malfunctioning, these types of schemes can be
unreliable,
can produce improper air/gas mixtures, and can cause a buildup of soot or
unburned carbon deposits or a dangerous condition.
There is a demand therefore, for a simple, reliable, and cost-effective way
of producing desirable combustion and aesthetic flame conditions of a
fireplace
unit or the like in an instantaneous manner from an initial cold start
condition
through a fully steady state condition. The present invention satisfies that
demand.
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SUMMARY OF THE INVENTION
The present invention has an objective of providing a desirable mixture of
combustion air to a fireplace as the fireplace transitions from a cold start
condition to a steady state, heated condition. One example of a fireplace that
s would be a suitable candidate for the invention is a model "DV360" fireplace
manufactured by CFM Corporation. It will be understood that the invention
contemplates any suitable gas fireplace or like device. More specifically, the
invention is directed to an automatic, heat activated air shutter assembly for
moderating the amount of air entering a burner assembly of a fireplace. The
air
shutter collar assembly is opened and closed by a bi-metal coil or a plurality
of bi-
metal coils attached to the shutter in such a fashion so that an increasing
amount
of air is permitted to enter the burner assembly as heat acting on the coil(s)
increases.
The fireplace may include a housing, which may take any suitable form as
needed or desired and may be in the form of an enclosure or framework, sized
and shaped according to a number of considerations. Examples of these
considerations include budget, space, aesthetic, mechanical, safety, and other
design and operating considerations. Generally, the housing is an enclosure or
structure in which or to which mechanisms and components are enclosed or
attached. The housing is also that which is attached at an installation
location.
The housing or box may be manufactured from a wide variety of materials,
including plastic resin suitable for the application, sheet metal, burner tube
material or any other material known to those skilled in the art.
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One embodiment of the housing includes a top panel, a bottom panel, a
back panel and opposing side panels. The two opposing side panels are further
optional depending on the application. The housing of this embodiment is sized
and shaped to accommodate a fire display box positioned therein. The fire
display box is designed to present to a viewer the impression of a working,
more
traditional fireplace. The fire display box may be open to the front for
viewing
purposes and may optionally be provided with a fixed or movable front panel or
panels, which may be at least in part transparent, translucent or opaque. For
purposes of this application, 'the front of the fireplace unit is that side of
the unit
through which the interior of the unit is at least partially viewable. It
should be
understood that the exemplary unit used to describe the invention herein will
be
similar to a conventional fireplace with a single front panel, through which
the
interior of the fireplace may be viewed. However, the invention also
contemplates a "dual-front" or "see-through" unit or other suitable units in
which it
is desirable to automatically control the flame appearance.
A fire display box is positioned in the housing. For purposes of this
application, the term "fire display box" will broadly signify the area similar
to the
portion or area found in a fuel-burning fireplace in which combustion takes
place
and from which the fire that is produced thereby may be viewed. Traditionally,
this area is known as a "firebox," "box," or "fireplace."
Combustion takes place in or near the firebox by way of a burner, which is
supplied with air and gas and preferably some form of pilot light or ignition
device
with which to ignite the air and gas mixture. A shutter is attached on or near
the
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burner or in the intake air pathway to control the flow of intake air into the
burner.
The shutter includes one or more bi-meta) coils attached thereto. When the
burner is first lit, the burner assembly, shutter and coils are at ambient
temperature and the shutter is in a closed condition. This condition permits a
reduced amount of intake air to enter the burner housing. The burner, shutter
and coils gradually warm to a heated condition and, in response, the coiis
function to open the shutter to provide an increased amount of intake air over
the
time the burner transitions from an initial ambient temperature to a steady
state
heated condition.
It has been found that the desired, yellow appearance of the flame may be
achieved in an instantaneous fashion by use of the bi-metal coil and shutter
assembly according to embodiments of the invention, "Instantaneous," for
purposes of this invention is considered about 1-5 minutes, which is a
significant
improvement over the prior art.
These and other advantages, as well as the invention itself, will become
apparent in the details of construction and operation as more fully described
and
claimed below. Moreover, it should be appreciated that several aspects of the
invention can be used in other applications where aesthetically pleasing
flames
wouid be desirable.
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V IZ 11 -LZGJ
According to one aspect of the present invention, there is provided a
gas heating unit, comprising: a combustion chamber; and a burner housing
assembly positioned to provide combustion to said combustion chamber, wherein
said burner housing assembly includes a burner housing and a gas and air
mixing
assembly in communication with said burner housing, said gas and air mixing
assembly including a mixing tube with an air inlet opening, a movable shutter
collar assembly positioned on said mixing tube, and a bi-metal coil spring
acting
on said shutter collar assembly for varying the air-gas ratio.
According to another aspect of the present invention, there is
lo provided a gas heating unit, comprising: a combustion chamber; and a burner
housing assembly positioned to provide combustion to said combustion chamber,
wherein said burner housing assembly includes a burner housing and a gas and
air mixing assembly in communication with said burner housing; said gas and
air
mixing assembly including a mixing tube assembly, said the mixing tube
assembly
including a mixing tube having at least one air opening formed at an outer end
thereof and a shutter collar assembly sized, shaped and positioned to seal
with
said at least one air opening of said mixing tube, said shutter collar
assembly
being attached to a bi-metal coil spring, said bi-metal coil spring being
responsive
to changes in temperature to move said shutter collar assembly relative to
said
mixing tube in response to an increase of temperature from an ambient
temperature so as to permit air to enter said at least one air opening.
According to still another aspect of the present invention, there is
provided a burner housing assembly for use in a heating unit, comprising: a
burner
housing and a gas and air mixing assembly in communication with said burner
housing; said gas and air mixing assembly including a mixing tube assembly,
said
the mixing tube assembly including a mixing tube having at least one air
opening
formed at an outer end thereof and a shutter collar assembly sized, shaped and
positioned to seal with said at least one air opening of said mixing tube,
said
shutter collar assembly being attached to a bi-metal coil spring, said bi-
metal coil
spring being responsive to changes in temperature to move said shutter collar
assembly relative to said mixing tube in response to an increase of
temperature
from an ambient temperature so as to permit air to enter said at least one air
opening.
6a
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BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 shows an embodiment of a gas fireplace suitable for use with
the burner assembly of the invention;
6b
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Fig. 2 shows a perspective view of an assembled burner housing
assembly made in accordance with one embodiment of the present invention;
Fig. 3 shows an expanded perspective view of the burner housing
assembly of Fig. 2;
s Fig. 4 shows an exploded view of a dual spring assembly, shutter collar
assembly and mixing tube assembly according to an embodiment of the
invention;
Fig. 5 shows a perspective view of the assembly of Fig. 4 assembled;
Fig. 6 shows a partial top view of the assembly of Fig. 5;
Fig. 7 shows an end view of the assembly of Fig. 4;
Fig. 8 shows a side view of the mixing tube assembly in an assembled
condition;
Fig. 9 shows a perspective view of a mixing tube assembly in an
expanded condition;
Fig. 10 shows a perspective view of a mixing tube;
Fig. 11 shows an end view of mixing tube;
Fig. 12 shows a first side view of a mixing tube;
Fig. 13 shows a second side view of a mixing tube rotated 90 degrees;
Fig. 14 shows an end view of a spring plate;
Fig. 15 shows a perspective view of a spring plate;
Fig. 16 shows a side view of a spring plate;
Fig. 17 shows a side view of a tube cap;
Fig. 18 shows the tube cap of Fig. 17 in an end view;
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Fig. 19 shows an expanded perspective view of another embodiment of a
mixing tube assembly and bimetal coil spring assembly;
Fig. 20 shows a side view of a spring bar;
Fig. 21 shows an end view of a spring bar;
Fig. 22 shows a perspective view of a spring bar;
Fig. 23 shows a top view of bimetal coil spring;
Fig. 24 shows a side view of the bimetal coil spring of Fig. 23; and
Fig. 25 shows an expanded view of the shutter collar assembly.
DETAILED DESCRIPTION OF A PRESENTLY PREFERRED EMBODIMENT
The present invention will now be described in detail with reference to
certain embodiments thereof as illustrated in the accompanying drawings. In
the
following description, numerous specific details are set forth in order to
provide a
thorough understanding of the present invention and how it may be applied to a
gas fireplace. It will be apparent, however, to one skilled in the art, that
the
present invention may be practiced without some or all of these specific
details.
In other instances, well-known process steps and/or structures have not been
described in detail to prevent unnecessarily obscuring the present invention.
Fig. 1 illustrates a gas-fueled heating unit, which in a preferred
embodiment is a fireplace in accordance with one embodiment of the present
invention. Referring to Fig. 1, a gas heating unit 60 includes a combustion
chamber 61 with sidewalls (not shown), a rear wall 66 and top and bottom walls
63 and 65. Simulated logs, e.g., ceramic gas logs 68 are arranged in a
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conventional manner over a burner housing assembly 100 according to an
embodiment of the invention. A glass front door (not shown) closes the
combustion chamber 61 and provides visual access thereto.
Surrounding the combustion chamber 61 is a unit housing or fireplace
s housing 67. Air circulation pathways are formed within the fireplace housing
67
in a conventional manner. One such pathway allows room air to be brought in
from the bottom front of the fireplace housing and beneath the combustion
chamber 61 (arrows 72). The room air is then directed along the rear of the
combustion chamber 61 (arrows 73). Finally, the room air is directed along the
top of the combustion chamber 61 (arrows 74) and back into the room. At this
point, the room air has been heated due to the placement of the pathway air
proximate to the heated combustion chamber 61.
In another pathway, combustion air (i.e., air entering the combustion
chamber 61) is brought in from the exterior of the building through a
concentric
is flue pipe assembly common to this type of fireplace. As will be described
below,
the combustion air can enter from one of two available ports. Once within the
fireplace housing 67, the combustion air travels a pathway immediately
outboard
of the room air pathways. That is, the inboard side of the combustion air
pathway includes the wall structure forming the outboard side of the room air
pathway. This placement also aids in the heating of the room air contained
within
the room air pathways. Combustion air travels downward through the rear of the
heating unit 60 (arrows 75), then into the combustion chamber 61 (arrow 76)
through combustion chamber air inlets 78 formed in a bottom portion of the
rear
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wall 66. The fireplace housing 67 has exterior sidewalls (not shown), top wall
82,
a bottom wall 83 and a rear wall 84.
Disposed within the combustion chamber 61 is a burner housing assembly
100 according to an embodiment of the invention. The burner housing assembly
100 includes a heat-activated mechanism 102 according to an embodiment of
the invention. The heat-activated mechanism 102 regulates the mixing of gas
and air entering the burner housing assembly 100 in response to changes in
temperature by changing the mixture of gas and air in a manner that will be
described in greater detail below.
Ignition of the gas and air mixed by the heat-activated mechanism 102
produces a yellow flame or flames 200 in an instantaneous fashion (i.e., in
about
1-5 minutes after initial ignition) relative to the prior art, which may
typically take
30 or more minutes to achieve. The mechanism 102 maintains the appearance
of the flames 200 from a start up condition of the unit through a steady state
condition.
Described herein is a fireplace assembly with a heat-activated
mechanism, which provides for a predetermined ratio of air and gas at a cold
start up condition and transitions to a heated and steady state condition in
response to changes in temperature, experienced by the mechanism. While the
above-described assembly is intended to be used with a fireplace, it is to be
realized that the described arrangement according to the embodiments of the
invention could be incorporated in other types of units, such as for example,
CA 02552492 2006-12-08
direct vent, natural vent and vent-less fireplace systems and even gas
operated
units which are not fireplaces.
Figure 2 shows an assembled burner housing assembly 100 according to
an embodiment of the invention that includes a burner housing 101 and an
s assembled gas and air mixing assembly 102. The burner housing assembly 100
includes a number of associated or attached components, the details of which
are provided in Fig. 3 and the following drawings. Generally, the burner
housing
assembly 100 includes a burner housing 101, which has a rectangular shape,
within which gaseous fuel and air are mixed at least in part through the
functioning of the gas and air mixing assembly 102. The burner housing 101
may be fastened together by welding, for example. Other suitable shapes of the
housing are contemplated.
Turning to Fig. 3, the burner housing 101 is provided with a port loading
channel 104, which fits atop the burner housing and closes the burner housing.
Preferably, the port loading channel 104 is provided with a sealant, (not
shown)
to effect a seal with burner housing 101. Port loading channel 104 includes a
plurality of port loading channel openings 106 formed therethrough for gas and
air to leave the burner housing in a pattern which may be designed and
intended
to produce desired flame patterns.
A port loading channel gasket 108 is positioned atop port loading channel
104. One or more ceramic tile 110 is positioned adjacent or atop the port
loading
channel gasket 108 at least in part to protect the burner housing assembly 100
from direct exposure to heat from flames. The one or more ceramic tile 110 is
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flanked by one or more burner tile gasket 112. The one or more ceramic tile
110
is held in place by first and second ceramic tile mounting angles 114, which
fasten to the burner housing 101 by conventional fasteners 116, such as
screws.
A securing bracket 118 attaches to the burner housing 101 and includes a pair
of
log spacer brackets 120, which log spacer brackets overlay ceramic tiles 110
when fastened to the securing bracket.
The burner housing assembly 100 may include other devices for
supporting an artificial log set (not shown) above the burner housing
assembly.
For example, a front log support bracket 122 may be mounted to the burner
housing 101 over the ceramic tile mounting angles 114.
The burner housing 101 includes a burner housing opening 126. The gas
and air mixing assembly 102 is disposed in the burner housing opening 126. A
spring plate gasket 128 is interposed between the burner housing 101 and gas
and air mixing assembly 102 to create a seal with the burner housing opening
126. Details of each of the above assemblies and elements of the burner
housing assembly 100 are provided hereinbelow.
Figs. 4-7 show the air and gas mixing assembly 102 in detail. The air and
gas mixing assembly 102 includes a mixing tube assembly 130, which is further
detailed in Figs. 8 and 9. The mixing tube assembly 130 includes mixing tube
132, which is an elongated cylinder shape. Upper and lower air openings 134,
136 are formed at an outer end 138 of the mixing tube 132. An annular or
washer shaped tube cap 140 is positioned at the outer end 138 of the mixing
tube 132.
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A shutter collar assembly 142 is positioned over the upper and lower air
openings 134, 136 in the size and shaped to closely the over the upper and
lower
air openings 134, 136. At ambient air temperatures the shutter collar assembly
142 is held closely against the mixing tube 132 so as to close off the upper
and
lower air openings 134, 136. The shutter collar assembly 142 is held in the
closed condition at ambient temperatures by respective upper and lower bi-
metal
coil springs 144, 146, which are configured to bias the shutter collar
assembly
142 in the depicted position. The shutter collar assembly 142, which is
disposed
on the upper air opening 134, may be considered a first shutter collar
io subassembly 142a and the shutter collar assembly, which is disposed over
the
lower air opening 136, may be considered a second shutter collar subassembly
142b.
Each of the upper and lower bi-metal coil springs 144, 146 are fastened to
a spring bar 148, which in turn is fastened to a spring plate 150. Spring
plate 150
has an opening 152 which is sized and shaped to receive the mixing tube 132.
It can be seen, especially in Fig. 7, that the bi-metal springs on 144, 146
hold the shutter collar assembly closely around the periphery of the mixing
tube
132 at the outer end 138 thereof (see Fig. 4). In this way, air is not drawn
into
the mixing tube 132 during operation because the shutter collar assembly 142
closes over the upper air are opening 134 and the lower air openings 136. The
bi-metal coil springs 144, 146 are constructed and oriented in such a fashion
to
uncoil and pull the shutter collar assembly 142 away from the mixing tube 132
thus exposing the upper air opening 134 and the lower air opening 136, which
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permits air to enter interior of the mixing tube 132, mix with gaseous fuel
and
enter the burner housing 101 (see Fig. 3, for example). The embodiment of the
gas and air mixing assembly 102 shown in Figs. 4-7 is intended for use with
natural gas, but may be adapted for use with LP gas, as in known in the art
and
is also shown below with reference to Fig. 19.
Figs. 8 and 9 show the mixing tube assembly 130. The mixing tube
assembly 130 includes a cylindrical mixing tube 132. The mixing tube 132 is
also
shown in Figs. 10-13. Referring then to Figs. 8-13, at the outer end 138 of
the
mixing tube 132 are formed a pair of cutaway sections, which when tube cap 140
io is attached to the outer end of the mixing tube cause the formation of
openings
134, 136. The tube cap 140 has a washer or annular shape with a cap opening
141 centrally located therethrough. Spring plate 150 is generally and L-shaped
bracket having a plate opening 152, which is sized to receive the mixing tube
132. A spring plate 150 is positioned close to the outer and 138 of the mixing
is tube 132. Welding, for example, may be used to assemble the mixing tube
assembly 132. Any other suitable fastening method may be used.
Figs. 14-16 show spring plate 150 in detail. Spring plate 150 has a spring
plate tube section 158 that includes plate opening 152. A spring plate bend
156
separates the spring plate tube section 158 from a spring plate spring section
20 160 at an angle of about 90 degrees. The spring plate spring section 160
includes a pair of spaced spring receiving tabs 154.
Figs. 17 and Fig. 18 show tube cap 140, which has a flat washer shape
and a centrally located cap opening 141. Tube cap 140 is attached to the outer
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end 138 of mixing tube 132 (see Fig. 8, for example). The attachment may be
accomplished in any suitable fashion, for example by welding.
Fig. 19 shows an embodiment of a mixing tube assembly and a partial
shutter collar assembly in detail and usable with LP gas (propane). The mixing
tube assembly 230 includes mixing tube 132, which is an elongated cylinder
shape. Upper and lower air openings 134, 136 are formed at an outer end 138 of
the mixing tube 132. An annular or washer shaped tube cap 240 is positioned at
the outer end 138 of the mixing tube 132. A manually adjustable choke sleeve
162 is provided on the mixing tube 132 and has the general shape of a
flattened
io ring with a pair of cutouts 164 corresponding in shape and size to the
upper and
lower air openings 134, 136. The choke sleeve 162 is slidably and rotatably
positioned on the mixing tube 132 and over the upper and lower air openings
134, 136 and when rotated can be used to cover or uncover the upper and lower
air openings and thus adjust how much of the openings are exposed. A set
screw 166 is provided in a slot 168 of the choke sleeve 162 to fix the choke
sleeve in place, preferably after adjustment for a desired air/fuel ratio.
Each of the upper and lower bi-metal coil springs 144, 146 are fastened to
a spring bar 148, which in turn is fastened to a spring plate 150. Spring
plate 150
has an opening 152 which is sized and shaped to receive the mixing tube 132.
The free ends 180 of the bi-metal coil springs 144, 146 occlude the upper and
lower air openings 134, 136 when in an initial start-up condition (i.e.,
ambient
temperature). As the temperature increases, the bi-metal coil springs 144, 146
CA 02552492 2006-12-08
unwind and draw away from the upper and lower air-openings 134, 136 to permit
entry of an increased volume of air to enter the mixing tube 132.
Figs. 20-22 show various views of spring bar 148. Spring bar 148 is an "L"
shaped bracket having a spring bar hole 170 for fastening the spring bar to a
spring plate (see 150 in Fig. 19, for example).
Figs. 23 and 24 show a bi-metal coil spring 144 according to an
embodiment of the invention. It should be noted that upper and lower bi-metal
springs 144, 146 (See Fig. 4, for example) are identical in material
composition
and geometric configuration in this example. For the fireplace used in the
above
example, it is desired to construct the bi-metal coil springs 144, 146 from a
material that withstands 1000 degrees F maximum temperature and about 800
degrees nominal temperature. The spring type is an ASTM-TM-1, available from
Atlanta Alloy Inc., and of a composite construction consisting of two or more
materials with different thermal expansion coefficients, and which unwinds
when
heated. Other bi-metal springs or the equivalent may be used. It should be
understood that the amount of movement of the spring and, in some
embodiments, the attached shutter assembly, will correspond to the bi-metal
materials used, the construction of the spring, and the temperature range
experienced by the spring. In other words, a spring used in the mechanism of
the invention may be lighter in construction or more sensitive to temperature
changes when a relatively lower range of temperature is experienced and a
heavier or less sensitive spring will be used when relatively higher range of
temperature change is experienced by the spring. In this manner, a properly
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controlled airflow and mixing ratio is maintained when applying the principles
described herein to different unit condiEions.
The coil springs 144, 146 are provided in the coiled configuration, in part
to be compact and usable in a small space, and in part to provide a large
amount
s of movement, or deflection for the temperature changes experienced by the
springs. Each of the bi-metal coil springs 144 include a mounting porCion 178
for
attaching to the spring receiving tab 154 of a spring plate 150 (see Fig. 15,
for
example) and spring bar 148. The attachment method is preferably welding to
provide the correct positional relationship for proper sealing of the shutter
collar
io assembly 142 to a respective upper and lower air opening 134, 136 (Fig. 4,
for
example). Other attachment methods may be employed, such as fasteners,
screws, rivets and so on. At an end opposite the mounting portion 178 is an
attachment portion 180 for attaching the bi-metal coil spring 144 to a shutter
collar assembly 142 (see Fig. 4, for example and Fig. 25).
15 Fig. 25 shows an expanded view of one half of a shutter collar assembly
142. The assembly 142 shown includes a shutter collar 172, which is a curved
metallic semi-circular member. Attached to an inside surface 174 of the
shutter
collar is a shutter gasket 176. The shutter gasket 176 is preferably a closed
cell
silicone sponge gasket of medium density.
20 Whilst endeavoring in the foregoing specification to draw attention to
those
features of the invention believed to be of particular importance it should be
understood that the invention extends to any patentable
feature or combination of features hereinbefore referred to and/or shown in
the
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drawings whether or not particular emphasis has been placed thereon. While the
apparatus and method herein disclosed forms a preferred embodiment of this
invention, this invention is not limited to that specific apparatus and
method, and
changes can be made therein without necessarily departing from the scope of
$ this invention.
Therefore, the foregoing is considered as illustrative only of the principles
of the invention. Further, since numerous modifications and changes will
readily
occur to those skilled in the art, it is not desired to limit the invention to
the exact
construction and operation shown and described, and accordingly, all suitable
modifications and equivalents may be resorted to, falling within the scope of
the
invention.
18
