Note: Descriptions are shown in the official language in which they were submitted.
CA 02684121 2009-10-28
THREE LAYER GLUED LAMINATE HEATING UNIT
BACKGROUND
Background and Relevant Art
[0001] The ability to distribute heat has provided a number of opportunities
for
increasing human comfort levels for certain activities and has made other
activities not
previously feasible able to be accomplished. One field where external heating
has
found particular use is in industries where individuals work with liquid or
semi liquid
materials. For example, painters will typically need to maintain paint between
certain
temperatures to accomplish effective painting and to protect the paint from
chemical
deterioration. Other individuals may need to work with materials at a given
temperature
where the materials are stored in various buckets, barrels, tanks, boxes, and
the like. In
other fields, individuals may need to thaw a surface, such as the ground, or
maintain the
surface between certain temperatures. For example, prior to pouring concrete,
the
ground must be thawed and free of snow and ice. Additionally, once poured, the
concrete must be maintained in a certain temperature range to ensure proper
curing.
[0002] Heating units of various types have been previously implemented for
heating
surfaces, such as the ground, roofs, and the like, and a variety of
containers, such as
buckets, barrels, tanks, boxes, and the like. One such heating unit is a
barrel warmer.
Typically barrel warmers are relatively long, narrow straps that wrap around a
barrel to
provide heat to the barrel and its contents. However, typical barrel warmers
only cover
a portion of the barrel wall. Barrel warmers constructed in this fashion rely
on the
conductive nature of the metallic barrel to distribute heat to the contents of
the barrel.
However, these types of barrel warmers typically result in overheating
materials at the
location of the barrel warmer while possibly under heating materials in other
portions of
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CA 02684121 2009-10-28
the barrel. In particular, temperatures up to 4000 F may be obtained at the
heating
elements of the barrel warmer. This can be a fire hazard depending on the
materials
used in the barrel warmer, or materials placed near a barrel being heated. To
regulate
the heat of materials in the barrel, the user may be required to stir the
materials in the
barrel so as to evenly mix different temperature materials. Additionally, if
more even
heat distribution is desired, multiple barrel warmers may be required.
However, this
requires the availability of multiple outlet receptacles and the use of
additional power.
100031 Another typical heating unit used to heat a surface, such as the
ground, for
example, is a glycol based heater. Glycol based heating systems use a boiler
system to
heat a propylene glycol liquid mixture. The propylene glycol mixture is then
circulated
through industrial hydronic hosing using a pumping system to heat the soil and
thaw
frozen ground, for example. However, glycol based heating systems suffer from
inefficient distribution of the heat stored in the glycol mixture. In
particular, heat is
most efficiently transferred to the surface in locations where the hose
contacts the
surface, but other surrounding areas receive less heat.
[0004] The subject matter claimed herein is not limited to embodiments that
solve
any disadvantages or that operate only in environments such as those described
above.
Rather, this background is only provided to illustrate one exemplary
technology area
where some embodiments described herein may be practiced.
BRIEF SUMMARY
[0005] One embodiment described herein is directed to a heating unit for use
in
providing evenly distributed heat to a surface or object. The heating unit
includes a first
pliable cover layer and a second pliable cover layer. A pliable electrical
heating
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CA 02684121 2009-10-28
element is disposed between the first and the second cover layers. The pliable
electrical
heating element includes a heat generating element for converting electrical
energy to
heat energy and a heat spreading element that is attached to the heat
generating element.
The heat spreading element comprises carbon that is thermally coupled to the
heat
generating element for distributing the heat energy. A thermal insulation
layer is
attached to a first side of the pliable electrical heating element and is
positioned
adjacent the first cover layer. Additionally, a receiving power connector is
electrically
connected to the heat generating element and is configured to couple to an
electrical
power source.
[0006] This Summary is provided to introduce a selection of concepts in a
simplified form that are further described below in the Detailed Description.
This
Summary is not intended to identify key features or essential features of the
claimed
subject matter, nor is it intended to be used as an aid in determining the
scope of the
claimed subject matter.
100071 Additional features and advantages will be set forth in the description
which
follows, and in part will be obvious from the description, or may be learned
by the
practice of the teachings herein. Features and advantages of the invention may
be
realized and obtained by means of the instruments and combinations
particularly
pointed out in the appended claims. Features of the present invention will
become more
fully apparent from the following description and appended claims, or may be
learned
by the practice of the invention as set forth hereinafter.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0008] In order to describe the manner in which the above-recited and other
advantages and features can be obtained, a more particular description of the
subject
matter briefly described above will be rendered by reference to specific
embodiments
which are illustrated in the appended drawings. Understanding that these
drawings
depict only typical embodiments and are not therefore to be considered to be
limiting in
scope, embodiments will be described and explained with additional specificity
and
detail through the use of the accompanying drawings in which:
100091 Figure 1 illustrates an exemplary embodiment of a heating unit
according to
the present invention;
[0010] Figure 2 illustrates a partially exploded view of the heating unit of
Figure 1;
[0011] Figure 3 illustrates an exploded view of some of the components of the
heating unit of Figure 1 showing the construction of the heating unit with
adhesive
layers;
[0012] Figure 4 illustrates details of a heat spreading element of the heating
unit of
Figure 1;
[0013] Figures 5A and 5B illustrate comparative alternate temperature
arrangements
for the heating unit of Figure 1:
[0014] Figures 6A and 6B illustrate various fasteners used in association with
the
heating unit of Figure 1.
DETAILED DESCRIPTION
[0015] Disclosed herein are embodiments of a heating unit for use in providing
evenly distributed heat to a surface or object. The heating unit can be
configured in a
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CA 02684121 2009-10-28
variety of shapes and sizes to provide heat to objects and surfaces that vary
in size and
shape. For example, embodiments include a heating unit configured to
substantially
cover the entire outer circumference of a barrel or bucket wall, including
substantially
the full height of the barrel or bucket. Other exemplary embodiments include a
heating
unit configured to substantially cover the sides of a box and, optionally, the
top and/or
bottom of the box to provide heat to the box and its contents. Still other
exemplary
embodiments include a heating unit configured to be positioned underneath, on
top of,
or otherwise adjacent to a surface to provide evenly distributed heat to the
surface, such
as the ground or a roof.
[0016] The heating unit includes a heating element which provides heat and
spreads
the heat over the surface of the heating unit. The heating unit may also
include an
insulation layer to prevent heat from being lost to an environment external to
the
surface, barrel, box, or other object which the heating unit is used to heat.
For example,
Figure 1 illustrates one embodiment of a heating unit configured as a barrel
or bucket
warmer 100 covering a barrel 10. While Figure 1 illustrates the heating unit
as a barrel
or bucket warmer, it will be appreciated that the heating unit can be sized,
shaped, or
otherwise configured to provide heat to other objects and/or surfaces, as
described
herein.
[0017] An example of components implemented in one embodiment is illustrated
in
Figures 2 and 3. These Figures illustrate the construction of the heating unit
including
materials used to assemble the heating unit. Figure 2 illustrates a partially
exploded
view illustrating the flexible nature of a heating unit 100 that includes a
first cover layer
102, an insulation layer 104, a heating element 106, and a second cover layer
108. In
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some embodiments, the heating element 106 includes a heat generating strip 114
and a
heat spreading element 122, each of which will be described in greater detail
below.
The heating unit 100 further includes an incoming electrical connector 110 and
an
outgoing electrical connector 112. While the example illustrated in Figure 2
is
illustrated as partially exploded, some finished embodiments may be
manufactured such
that the insulation layer 104 and the heating element 106 may be sealed
between the
first cover layer 102 and the second cover layer 108. Sealing processes and
details will
be discussed in more detail below.
[0018] Figure 3 illustrates a fully exploded view of the heating unit 100 so
as to
more clearly illustrate the individual components of the heating unit 100. As
illustrated
in Figure 3, first and second cover layers 102 and 108 are generally planar
sheets of
material that are disposed on opposing sides of the internal components of
heating unit
100. During construction of heating unit 100, first cover layer 102 is
positioned as
illustrated in Figure 3. Next, insulation layer 104 is positioned on top of
first cover
layer 102 and heating element 106 is then positioned on top of insulation
layer 104.
Finally, second cover layer 108 is positioned on top of heating element 106.
With the
various components of heating unit 100 so positioned, the peripheral edges of
first and
second layers 102 and 108 can be joined, sealed, or otherwise closed.
[0019] Heating unit 100, constructed as described herein, can be used in
numerous
applications that require heat to be transferred to an object or surface. As
described
herein, the various components of heating unit 100 are flexible such that
heating unit
100 can be wrapped around objects, laid on top, beneath, or hung adjacent
objects or
surfaces, and rolled or folded up when not in use. In order to ensure that
heating unit
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100 and its various components retain their shape and their positions relative
to one
another, the various components of heating unit 100 can be attached to one
another. For
example, the various components of heating unit 100 can be glued, bonded, or
otherwise held together. Attaching the components of heating unit 100 together
helps to
prevent the components from moving relative to one another within heating unit
100.
[0020] For example, attaching heating element 106 to insulation layer 104
ensures
that heating element 106 will stay positioned next to insulation layer 104 and
will not
sag, bunch, or otherwise move within heating unit 100. In particular, because
insulation
layer 104 is formed of a stiffer material than heating element 106, attaching
heating
element 106 to insulation layer 104 provides stiffness to heating element 106.
While
insulation layer 104 is referred to as being formed of a "stiffer" material,
it will be
appreciated that in some embodiments insulation layer 104 may still be
flexible such
that it can be wrapped around a barrel or folded around a box, for example.
Similarly,
heat generating strip 114 and heat spreading element 122 can be attached to
one another
to ensure that heat generating strip 114 is properly positioned on heat
spreading element
122, even after heating unit 100 is rolled, folded, and used several times.
Likewise,
heating element 106 and/or insulation layer 104 can be attached to first
and/or second
cover layers 102 and 108 to prevent the internal components of heating unit
100 from
moving within first and second cover layers 102 and 108.
[0021] Figure 3 illustrates one exemplary embodiment in which various
components of heating unit 100 are attached together. For convenience of
illustration,
incoming electrical connector 110 and outgoing electrical connector 112 are
omitted
from Figure 3. In the embodiment illustrated in Figure 3, there are two
interfaces
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between the heating unit components for attachment between the components. As
used
herein, an attachment interface is a surface where two or more components of
heating
unit 100 are attached together. The first attachment interface 136 is between
the top
surface of insulation layer 104 and the bottom surface of heating element 106.
As noted
herein, heating element 106 includes a heat generating strip 114 mounted on a
heat
spreading element 122. In the illustrated embodiment, the heat generating
strip 114 is
mounted on the bottom surface of heat spreading element 122 such that heat
generating
strip 114 is positioned between heating spreading element 122 and insulation
layer 104.
Attachment interface 136 is therefore between the top surface of insulation
layer 104
and the bottom surface of heat spreading element 122, with heat generating
element 114
mount on heat spreading element 122 therebetween.
[0022] The second attachment interface 140 is between the top surface of heat
spreading element 122 and the bottom surface of second cover layer 108. In
other
embodiments, there is only the first attachment interface 136. Still in other
embodiments, there are additional attachment interfaces, such as between the
bottom
surface of insulation layer 104 and the top surface of first cover layer 102.
[0023] Attachment interfaces 136 and 140 can be created by attaching the above
identified components of heating unit 100 in any suitable manner so that the
components maintain their relative positions one to another. In one exemplary
embodiment, attachment interfaces 136 and 140 are created using an adhesive
between
the components of heating unit 100. One such adhesive suitable for attaching
together
the components of heating unit 100 is 30-NF FASTBONDTM available from 3M
located
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in St. Paul, Minnesota. FASTBONDTM is a non-flammable, heat resistant,
polychloroprene base adhesive.
[0024] In order to properly adhere the components of heating unit 100 together
with
FASTBONDTM, the interfacing surfaces should be clean and dry. With the
surfaces
prepared, a uniform coat of FASTBONDTM is applied to both interfacing
surfaces.
After applying, the FASTBONDTM is allowed to dry completely, which typically
takes
about 30 minutes. Once the FASTBONDTM on both surfaces is dry, the two
FASTBONDTM coated surfaces are joined together.
[0025] For example, when attaching insulation layer 104 to heat spreading
element
122, a coat of FASTBONDTM is applied to the top surface of insulation layer
104 and
the bottom surface of heat spreading element 122 over the top of heat
generating strip
114. Once the FASTBONDTM on each surface is dry, heat spreading element 122 is
positioned on top of insulation layer 104 and the two layers of FASTBONDTM
adhere to
one another. The same process can be followed to attach second cover layer 108
to the
top surface of heat spreading element 122 or to attach the first cover layer
102 to the
bottom surface of insulation layer 104.
[0026] In the illustrated embodiment, second cover layer 108 is attached to
heating
element 106 and heating element 106 is attached to insulation layer 104.
Notably,
however, insulation layer 104 and heating element 106 can be left unattached
from first
and/or second cover layers 102 and 108. Not attaching insulation layer 104 and
heating
element 106 to first and/or second cover layers 102 and 108 provides for
flexibility and
give in heating unit 100 when heating unit 100 is folded, rolled, or wrapped
around an
object. Specifically, heating unit 100 is configured to be wrapped around an
object such
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CA 02684121 2009-10-28
that second cover layer 108 is adjacent the object and first cover layer 102
is positioned
away from the object (see Figure 1 in which first cover layer 102 is showing).
When
first and/or second cover layers 102 and 108 are not attached to insulation
layer 104
and/or heating element 106, first and/or second cover layers 102 and 108 are
able to
move relative to insulation layer 104 and heating element 106 and stretch as
heating
unit 100 is wrapped around an object. In other embodiments, however,
insulation layer
104 and first cover layer 102 are attached to one another while heating
element 106 and
second cover layer 108 are attached to one another. For example, when heating
unit
100 is used on flat surfaces, such as the ground or a roof, the need for first
and second
cover layers 102 and 108 to be able to move relative to insulation layer 104
and heating
element 106 is not as great.
[0027] The following discussion will now treat additional details and
embodiments
of the various components of the heating unit 100. Referring now to Figure 4
and as
noted above, in some embodiments the heating element 106 includes a heat
generating
strip 114. The heat generating strip 114 may be, for example, an electro-
thermal
coupling material or resistive element. In some embodiments, the heat
generating strip
may be a copper, copper alloy or other conductor. In one embodiment, the
conductor is
a network of copper alloy elements configured to generate about 9W of power
per linear
foot of the heat generating strip. This may be achieved by selection of
appropriate
alloys for the heat generating element 114 in combination with selection of
appropriate
heat generating element wire sizes and circuit configurations. The conductor
may
convert electrical energy to heat energy, and transfer the heat energy to the
surrounding
environment. Alternatively, the heat generating element 114 may comprise
another
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conductor, such as semiconductors, ceramic conductors, other composite
conductors,
etc., capable of converting electrical energy to heat energy. The heat
generating strip
114 may include one or more layers for electrical insulation, temperature
regulation,
and ruggedization.
[0028] Notably, other heat sources may be used in addition to or as
alternatives to
the heat generating strip. For example, some embodiments may include the use
of
exothermic chemical reactions to generate heat or heating tubes which a heated
liquid
runs through.
[0029] With continuing reference to Figure 4, the heat generating strip 114 is
illustrated with two heat generating conductors 116 and 118. One of the two
conductors
is connected to a first terminal of the incoming electrical connector 110
while the other
conductor is connected to a second terminal of the electrical connector 110.
The first
and second terminals may be connected to electrical sources as appropriate,
such as
generator supplied AC or DC sources, batteries, power inverters, etc. The two
conductors 116 and 118 may be connected at one end to create a closed circuit
allowing
current to flow through the two conductors to generate heat.
[0030] In the example illustrated in Figure 4, the two conductors are
connected
through a thermostat 120. In this example, the thermostat 120 includes a bi-
metal strip
based temperature control that disconnects the two conductors 116 and 120 at a
pre-
determined temperature. Examples of predetermined temperatures may be 90 F,
110 F,
130 F, and 160 F. Notably, these are only examples, and other temperatures may
be
alternatively used. This can be used to regulate the temperature of the
heating unit 100
to prevent overheating, or to maintain the temperature at a temperature of
about the pre-
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CA 02684121 2009-10-28
determined temperature. Embodiments may be implemented where the temperature
is
determined by selecting a thermostat 120 with a fixed temperature rating.
Other
embodiment may be implemented where the temperature setting of the thermostat
can
be adjusted to a predetermined temperature at manufacturing time. In some
embodiments, the thermostat may be user accessible to allow a user to adjust
the
thermostat settings. While in the example illustrated the thermostat is
located at the
ends of the conductors 116 and 118, it should be appreciated that in other
embodiments
the thermostat may be placed inline with one of the conductors 116 and 118.
Additionally, some embodiments may include low voltage control circuitry
including
temperature control functionality, which controls application of power to the
conductors
116 and 118 to regulate temperature.
100311 It should further be appreciated that embodiments may be implemented
where other temperature or current protections are included. For example,
embodiments may include magnetic and/or thermal circuit breakers, fuses,
semiconductor based over-current protection, ground fault protection, arc
fault
protection, etc. In some embodiments, these may be located at the ends of the
conductors 116 and 118 or inline with one or more of the conductors 116 and
118 as
appropriate.
[0032] Additionally, controlling temperature may be accomplished by
controlling
the density of the heat generating element 114. This may be accomplished by
controlling spacing between different portions of the heat generating element
allowing
for more or less material used for the heat generating element 114 to be
included in the
heating unit 100. This method may be especially useful when heat generating
elements
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have a constant Wattage output per length of heat generating element. Thus a
longer
heat generating element 114 provides more heat than a shorter heat generating
element
114. Figures 5A and 5B illustrate a comparative example where two alternative
embodiments are illustrates. Each of the embodiments illustrates a heating
unit 100 of
the same size, but with different heat generating elements densities. The
first
embodiment illustrates a heating element 106A with a less dense heat
generating
element 114A, while the second embodiment illustrates a heating element 106B
with a
more dense heat generating element 114B.
[0033] Returning attention to Figure 4, as noted above, the electrical heating
element 106 may further include a heat spreading element. In general terms,
the heat
spreading element 122 is a layer of material capable of drawing heat from the
heat
generating element 114 and distributing the heat energy away from the heat
generating
element 114. Specifically, the heat spreading element 122 may comprise a
metallic foil,
wire mesh, carbon mesh, graphite, a composite material, or other material.
[0034] The heat-spreading element 122 in one embodiment is an electrically-
conductive material comprising carbon. Graphite is one example of an
electrically-
conductive material comprising carbon. However, other suitable materials may
include
carbon-based powders, carbon fiber structures, or carbon composites. Those of
skill in
the art will recognize that material comprising carbon may further comprise
other
elements, whether they represent impurities or additives to provide the
material with
particular additional features. Materials comprising carbon may be suitable so
long as
they have sufficient thermal conductivity to act as a heat-spreading element.
In one
embodiment, the material comprising carbon comprises sufficient electrical
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conductivity to act as a ground connection, as will be discussed in more
detail below.
The heat-spreading element 122 may further comprise a carbon derivative, or a
carbon
allotrope.
[0035] One example of a material suitable for a heat spreading element 122 is
a
graphite-epoxy composite. The in-plane thermal conductivity of a graphite-
epoxy
composite material is approximately 370 watts per meter per Kelvin, while the
out of
plane thermal conductivity of the same material is 6.5 watts per meter per
Kelvin. The
thermal anisotropy of the graphite/epoxy composite material is then 57,
meaning that
heat is conducted 57 times more readily in the plane of the material than
through the
thickness of the material. This thermal anisotropy allows the heat to be
readily spread
out from the surface which in turn allows for more heat to be drawn out of the
heating
element 114.
100361 The heat spreading element 122 may comprise a material that is
thermally
isotropic in one plane. The thermally isotropic material may distribute the
heat energy
more evenly and more efficiently. One such material suitable for forming the
heat
spreading element 122 is GRAFOIL available from Graftech Inc. located in
Lakewood, Ohio. In particular, GRAFOIL is a flexible graphite sheet material
made
by taking particulate graphite flake and processing it through an
intercalculation process
using mineral acids. The flake is heated to volatilize the acids and expand
the flake to
many times its original size. The result is a sheet material that typically
exceeds 98%
carbon by weight. The sheets are flexible, lightweight, compressibly
resilient,
chemically inert, fire safe, and stable under load and temperature. The sheet
material
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typically includes one or more laminate sheets that provide structural
integrity for the
graphite sheet.
[0037] Due to its crystalline structure, GRAFOIL is significantly more
thermally
conductive in the plane of the sheet than through the plane of the sheet. This
superior
thermal conductivity in the plane of the sheet allows temperatures to quickly
reach
equilibrium across the breadth of the sheet.
100381 Typically, the GRAFOIL will have no binder, resulting in a very low
density, making the heated cover relatively light while maintaining the
desired thermal
conductivity properties. For example, the standard density of GRAFOIL is
about 1.12
g/ml. It has been shown that three stacked sheets of 0.030" thick GRAFOIL C
have
similar thermal coupling performance to a 0.035" sheet of cold rolled steel,
while
weighing about 60% less than the cold rolled steel sheet.
[0039] Another product produced by GrafTech Inc. that is suitable for use as a
heat
spreading element 122 is EGRAF SPREADERSHIELDTM. The thermal conductivity
of the SPREADERSHIELD TM products ranges from 260 to 500 watts per meter per
Kelvin within the plane of the material, and that the out of plane (through
thickness)
thermal conductivity ranges from 6.2 down to 2.7 watts per meter per Kelvin.
The
thermal anisotropy of the material ranges from 42 to 163. Consequently, a
thermally
anisotropic planar heat spreading element 122 serves as a conduit for the heat
within the
plane of the heat spreading element 122, and quickly distributes the heat more
evenly
over a greater surface area than a foil. The efficient planar heat spreading
ability of the
planar heat spreading element 122 also provides for a higher electrical
efficiency, which
facilitates the use of conventional power supply voltages such as 120 volts on
circuits
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protected by 20 Amp breakers, instead of less accessible higher voltage power
supplies.
In some embodiments, the heat spreading element 122 is a planar thermal
conductor. In
certain embodiments, the graphite may be between 1 thousandth of an inch thick
and 40
thousandths of an inch thick. This range may be used because within this
thickness
range the graphite remains pliable and durable enough to withstand repeated
rolling and
unrolling as the heating unit 100 is unrolled for use and rolled up for
storage.
[0040] The heat spreading element 122 may comprise a flexible thermal
conductor.
In certain embodiments, the heat spreading element 122 is formed in strips
along the
length of the heat generating element 114. In alternative embodiments, the
heat
spreading element 122 may comprise a contiguous layer.
[0041] In some embodiments, the heat spreading element 122 may also include
functionality for conducting electrical energy and converting electric energy
to thermal
energy in a substantially consistent manner throughout the heat spreading
element.
Graphite heat spreading elements may be particularly well suited for these
embodiments. In such an embodiment, a heat generating element 114 may be
omitted
from the heating unit 100 as the heat spreading element 122 serves the
purposes of
conveying current, producing heat due to resistance, and evenly distributing
the heat.
[0042] The small size and thickness of the graphite minimizes the weight of
the heat
spreading element 122. The graphite containing heat spreading element may be
pliable
such that the graphite can be rolled lengthwise without breaking the
electrical path
through the graphite.
[0043] In some embodiments, the heat spreading element 122 may include an
insulating element formed of a thin plastic layer on both sides of the heat-
spreading
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element 122. The insulating element may additionally provide structure to the
heat-
spreading material used in the heat spreading element 122. For example, the
insulating
element may be polyethylene terephthalate (PET) in the form of a thin plastic
layer
applied to both sides of heat-spreading element 122 comprising graphite. Those
of skill
in the art will appreciate that such a configuration may result in the
insulating element
lending additional durability to the heat-spreading element 122 in addition to
providing
electrical insulation, such as electrical insulation from the electrical
current in the heat
generating element 114. It should be noted that the heating generating element
114 may
include its own electrical insulation as well as described above.
[0044] In some embodiments, the heat spreading element 122 may include a heat
conducting liquid such as water, oil, grease, etc.
[0045] In certain embodiments, the heat generating element 114 is in direct
contact
with the heat spreading element 122 to ensure efficient thermo-coupling.
Alternatively,
the heat spreading element 122 and the heat generating element 114 are
integrally
formed. For example, the heat spreading element 122 may be formed or molded
around
the heat generating element 114. Alternatively, heat generating strip 114 and
the heat
spreading element 122 may be adhesively coupled.
[0046] Notably, while temperature may be controlled with the use of
thermostats as
described above, other embodiments may implement other design criteria to
control
temperature. For example, some embodiments may use appropriate selection of
the
heat spreading element 122 and/or the arrangement of the heat generating
element 114.
Illustratively, the heat retention properties of the heat spreading element
122 may be a
factor in regulating temperatures at which a heating unit 100 will operate.
Further, the
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density of the heat generating element 114 with respect to the size of the
heating unit
100 or the heat spreading element 122 can be used set the operating
temperatures or to
regulate temperatures.
100471 Returning once again to Figures 2 and 3, Figures 2 and 3 illustrate an
insulating layer 104. The insulating layer 104 may be used to reflect or
direct heat or to
prevent heat from exiting in an undesired direction. For example, it may be
desirable to
have all or most of the generated heat be directed towards a particular
surface of the
heating unit 100. In the embodiment illustrated in Figures 1, 6A, and 6B, for
example,
it may be desirable to direct heat towards the wall of the barrel 10 while
directing heat
away from an exterior environment in which the barrel is located. In other
embodiments of the heating unit, it may be desirable to direct heat towards a
surface,
such as the ground, while directing heat away from air above the surface. In
the
example illustrated, it may be desirable to have heat directed towards the
side of the
heating unit 100 which includes the second cover layer, while directing heat
away from
the side that includes the first cover layer. The insulating layer 104 may be
used to
accomplish this task. Some exemplary embodiments of the heating unit have been
implemented where about 95% of heat generated is directed towards a desired
surface
of the heating unit.
[0048] The insulating layer 104 may include a sheet of polystyrene, cotton
batting,
Gore-Tex , fiberglass, foam rubber, etc. In certain embodiments, the
insulating layer
104 may allow a portion of the heat generated by the heat generating element
114 to
escape the top of the second cover layer 108 if desired. For example, the
insulating
layer 104 may include a plurality of vents to transfer heat to the second
cover layer 108.
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In certain embodiments, the insulating layer 104 may be integrated with either
the first
cover layer 102 or the second cover layer 108. For example, the first cover
layer 102
may include an insulation fill or batting positioned between two films of
nylon.
[0049] In some embodiments, first and second cover layers 102 to 108 may
comprise a textile fabric. The textile fabric may include natural or synthetic
products.
For example, the first and second cover layers 102 to 108 may comprise burlap,
canvas,
cotton or other materials. In another example, first and second cover layers
102 to 108
may comprise nylon, vinyl, or other synthetic textile material. The first and
second
cover layers 102 to 108 may comprise a thin sheet of plastic, metal foil,
polystyrene, or
other materials.
[0050] In manufacturing the heating unit 100, the heating element 106 and
insulation layer 104 may be sealed between the first and second cover layers
102 and
108. As illustrated in Figures 2 and 3, the first and second cover layers 102
and 108
extend slightly beyond the heating element 106 and insulation layer 104. This
allows
the first and second cover layers 102 and 108 to be sealed, such as by using
an adhesive,
heat welding, or another other appropriate method or combination of methods.
[0051] Additionally, the heating unit 100 may be constructed such that the
first and
second cover layers 102 and 108 may include one or more fasteners 124 for
hanging,
securing, or connecting the heating unit 100. In some embodiments, the
fasteners 124
may be attached or formed into the corners of the heating unit 100.
Additionally,
fasteners 124 may be distributed about the perimeter of the heating unit 100.
In some
embodiments, the fastener 124 is a hook and loop fastener such as VELCRO . For
example, the heating unit 100 may include a hook fabric on one side and a loop
fabric
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on an opposite side. In other alternative embodiments, the fastener 124 may
include
grommets, snaps, zippers, adhesives, or other fasteners. Further, additional
objects may
be used with the fasteners to accomplish fastening. For example, when grommets
are
used, elastic cord, such as fixed or adjustable bungee cord may be used to
connect to
grommets on opposite sides of the heating unit 100. This may be used, for
example, to
securely wrap the heating unit around objects, such as barrels, buckets, or
boxes.
Alternatively, stakes, hooks, or other suitable devices can be used in
connection with
fastener 124 to secure heating unit 100 to the ground, for example.
[0052] Figures 1, 6A, and 6B illustrate a number of fastener arrangements that
may
be implemented. For example, Figure 1 illustrates a first portion of the
heating unit 100
overlapping an opposing portion of the heating unit 100, and being attached to
the
opposing portion by snap fasteners 124. Figure 6A illustrates a first portion
of the
heating unit 100 overlapping an opposing portion of the heating unit 100.
Grommet
fasteners 124 are secured to the opposing portions of the heating unit 100 and
set away
from the edges of the heating unit 100 such that elastic cords 134 can be used
to secure
the opposing portions. Figure 6B illustrates an example where opposing
portions of the
heating unit 100 are permanently fastened. In this case, grommet fasteners 124
are
secured to opposing portions, where a single grommet may be secured to both
opposing
portions such that the heating unit permanently maintains a substantially
wrapped
shape.
[0053] In some embodiments, the first cover layer 102 may be positioned at the
top
of the heating unit 100 and the second cover layer 108 may be positioned on
the bottom
of the heating unit 100. In certain embodiments, the first cover layer 102 and
the
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second cover layer 108 may comprise the same or similar material.
Alternatively, the
first cover layer 102 and the second cover layer 108 may comprise different
materials,
each material possessing properties beneficial to the specified surface
environment.
[00541 For example, the first cover layer 102 may comprise a material that is
resistant to sun rot such as such as polyester, plastic, and the like. The
second cover
layer 108 may comprise material that is resistant to mildew, mold, and water
rot such as
nylon. The cover layers 102 and 108 may comprise a highly durable material.
The
material may be textile or sheet, and natural or synthetic. For example, the
cover layers
102, 108 may comprise a nylon textile. Additionally, the cover layers 102, 108
may be
coated with a water resistant or waterproofing coating. For example, a
polyurethane
coating may be applied to the outer surfaces of the cover layers 102, 108.
Additionally,
the top and bottom cover layers 102, 108 may be colored, or coated with a
colored
coating such as paint. In some embodiments, the color may be selected based on
heat
reflective or heat absorptive properties. For example, the top layer 102 may
be colored
black for maximum solar heat absorption. The bottom layer 102 may be colored
grey
for a high heat transfer rate or to maximize heat retention beneath the cover.
[0055] The embodiment shown in Figures 1-3 includes a 7 foot power cord 132
connected to the heat generating element 114. Other cord lengths may also be
implemented within the scope of embodiments of the invention. The power cord
may
additionally be connected to an incoming electrical connector 110 such as an
AC power
plug, bare wire connector, alligator clip connectors, a cigarette lighter plug
connector or
other appropriate connector for connecting the power cord to a source of
power.
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100561 Notably, some embodiments may be implemented with interchangeable
incoming electrical connectors. For example, embodiments may include a kit
which
includes a heating unit 100 with a two pin auto connector. The kit may further
include a
wire without an additional connector connected to a mating two pin auto
connector, a
set of alligator clips connected to a mating two pin auto connector, and a
cigarette
lighter plug connected to a mating two pin auto connector. A user can then
select an
appropriate incoming electrical connector 110. For example, a user may select
the wire
without an additional connector if the heating unit is to be hard wired to an
electrical
system, such as an automobile, boat, or other electrical system. Cigarette
lighter plugs
or alligator clip connectors could be selected for more temporary connectors.
[0057] Some embodiments may also include various fault protections. For
example, embodiments may include an incoming electrical connector 110 which
includes ground fault circuit interruption capabilities so as to make the
heating unit 100
suitable for use in wet or outdoor environment. Embodiments may include over
current
protection such as breakers or fuses. Embodiments may include arc fault
circuit
interruption capabilities to address problems related to fatigue of wires or
crushing of
wires.
[0058] Embodiments may further include provisions for grounding the heating
unit
100. For example, the heating unit is illustrated in Figures 1-3 includes an
incoming
electrical connector in the form an AC plug, which includes two power
terminals 128
and a grounding terminal 130. The power cord 132 may include three conductors,
one
connected to each power terminal 128, and the third connected the grounding
terminal
130. The two conductors connected each to a respective power terminal 128
connect as
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CA 02684121 2009-10-28
described above to the heat generating element 114. The third conductor may be
connected so as to ground the heating unit 100. This may be done, for example
by
including an electrically conductive layer (not shown) in the heating unit 100
which is
electrically connected to the grounding terminal 130.
[0059] In an alternative embodiment, due to the electrically conductive nature
of the
heat spreading element 122 when a graphite based material is used for the heat
spreading element 122, the grounding terminal 130 may be electrically coupled
to the
heat spreading element 122. This may be accomplished in one example, by using
a
ground coupling in the form of a spade connector or other connector which
passes
through a protective layer of the heat spreading element so as to be in
electrical contact
with the conductive portions of the heat spreading element 122. In one
embodiment,
the ground couplings comprise planar rectangular metal connection blades that
would
normally be used as the hot and/or neutral connection blades of a power
coupling such
as a power coupling which connects to a power source. In one embodiment,
ground
coupling spade connector further comprises barbs configured to cut into the
heat-
spreading element 122 and engage the heat-spreading element 122 such that the
blade
does not come loose. In alternative embodiments, the blade may be connected to
the
heat-spreading element 122 with an adhesive that does not electrically
insulate the heat-
spreading element 122 from the blade. In addition, the plane of the blade may
be placed
parallel to the plane of the heat-spreading element 122 such that a maximum
amount of
the surface area of the blade is in direct contact with the heat-spreading
element 122.
Such a configuration may increase the contact area between the two surfaces
and results
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CA 02684121 2009-10-28
in a better electrical and physical connection. Furthermore, such a
configuration can
leverage the lower in-plane resistivity of the heat-spreading element 122.
[0060] Additionally, some embodiments may include an outgoing electrical
connector 112. This may be used, for example to allow chaining of heating
units
together. In the example illustrated, the outgoing electrical connector 112 is
connected
electrically to the incoming electrical connector 110 through conductors 126
passing
through the heating unit 100. Other embodiments may allow the incoming
electrical
connector 110 and outgoing electrical connector 112 to be more or less
proximate to
each other as appropriate.
[0061] A grounding terminal 132 of the outgoing electrical connector 112 may
be
electrically connected to the grounding terminal 130 of the incoming
electrical
connector 110. This may be accomplished by wiring the two terminals together
or
connecting both grounding connectors to the same grounding surface, such as a
grounding layer, or to the heat spreading element 122 as described above.
[0062] Some embodiments may further include timing circuitry such that a user
can
select when heating should occur. The timer may be an electronic controlled
device
supplied by the electrical connector 112 and may include internal switching
such as
relays or solid state switches for supplying power to the heat generating
strip 114.
[0063] The present invention may be embodied in other specific forms without
departing from its spirit or essential characteristics. The described
embodiments are to
be considered in all respects only as illustrative and not restrictive. The
scope of the
invention is, therefore, indicated by the appended claims rather than by the
foregoing
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description. All changes that come within the meaning and range of equivalency
of the
claims are to be embraced within their scope.
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