U.S. patent application number 13/957557 was filed with the patent office on 2013-12-12 for package heating device and chemical compositions for use therewith.
This patent application is currently assigned to HeatGenie, Inc.. The applicant listed for this patent is HeatGenie, Inc.. Invention is credited to Travis Bookout, Brendan Coffey, Krzysztof Czeslaw Kwiatkowski.
Application Number | 20130327312 13/957557 |
Document ID | / |
Family ID | 45441784 |
Filed Date | 2013-12-12 |
United States Patent
Application |
20130327312 |
Kind Code |
A1 |
Coffey; Brendan ; et
al. |
December 12, 2013 |
PACKAGE HEATING DEVICE AND CHEMICAL COMPOSITIONS FOR USE
THEREWITH
Abstract
A heating device comprises a heating chamber defining an
interior space for receiving and storing a substance to be heated,
a heater for use as a source of heat which includes a reaction
chamber, a solid state reaction composition disposed within the
reaction chamber such that it is physically isolated from and in
thermal communication with the interior space of the heating
chamber, an activation mechanism in communication with the
composition disposed within the reaction chamber, and wherein the
reaction composition is inert until the activation mechanism is
actuated. Activation mechanism comprises an actuator having a user
interface portion and an actuation portion, and the actuation
portion carries a reaction initiation material that, when assembled
with the heater, is capable of initiating a chemical reaction in
the chemical composition when the actuation portion is actuated by
a user.
Inventors: |
Coffey; Brendan; (Austin,
TX) ; Kwiatkowski; Krzysztof Czeslaw; (Austin,
TX) ; Bookout; Travis; (Kyle, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HeatGenie, Inc. |
Austin |
TX |
US |
|
|
Assignee: |
HeatGenie, Inc.
Austin
TX
|
Family ID: |
45441784 |
Appl. No.: |
13/957557 |
Filed: |
August 2, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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13177502 |
Jul 6, 2011 |
8555870 |
|
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13957557 |
|
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61361909 |
Jul 6, 2010 |
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Current U.S.
Class: |
126/263.01 |
Current CPC
Class: |
C09K 5/18 20130101; F24V
30/00 20180501; A47J 36/28 20130101 |
Class at
Publication: |
126/263.01 |
International
Class: |
F24J 1/00 20060101
F24J001/00 |
Claims
1. A heater for use as a source of heating a substance contained in
a heating device, the heater comprising: a housing defining an
exterior shape of the heater and an interior space, the housing
comprising a canister portion and a lid portion; a solid state
chemical heating composition disposed within the housing; and an
activation mechanism capable of communication with the composition
and having an actuator and disposed within the housing such that
the actuator is actuable from outside of the heating device when
heater is coupled to the heating device; wherein the canister and
the lid of housing are sealed together.
2. The heater of claim 1 wherein the lid portion is flexible.
3. The heater of claim 2 wherein the actuator is disposed adjacent
to the lid portion and is actuable by flexing the lid portion.
4. The heater of claim 3 wherein the heater further includes a
flexible insulating layer between the solid state chemical heating
composition and the lid portion.
5. The heater of claim 3, wherein the composition is comprised of a
first fuel component, a second fuel component, a solid oxidizer,
and a thermal diluent.
6. The heater of claim 3, wherein the activation mechanism
comprises a piston, a blister pouch containing a first reaction
initiation material, and a pellet comprising a second reaction
initiation material and in communication with the solid state
chemical heating composition; the piston, blister pouch and pellet
being arranged within the heater such that when the lid portion is
depressed, the piston is depressed and ruptures the blister pouch,
thereby allowing the first reaction initiation material to contact
the pellet and initiate a chemical reaction between the first
reaction initiation material and the second reaction initiation
material that generates sufficient thermal energy to initiate
reaction of the solid state chemical heating composition.
7. The heater of claim 6, wherein the pellet further contains
fibrous particulates to promote wicking and rapid absorption of
first reaction initiation material.
8. The heater of claim 1, further comprising a mechanism to
automatically shut down the heater when a predetermined threshold
temperature is reached by the reaction of the solid state chemical
heating composition.
9. The heater of claim 8, wherein the mechanism comprises an
intumescent material coated on an interior surface of the
heater.
10. The heater of claim 8, wherein the mechanism comprises an
intumescent material incorporated into the solid state chemical
heating composition.
11. The heater of claim 8, wherein the mechanism comprises a flame
retardant incorporated into the heater to slow the reaction of the
solid state chemical heating composition by gas phase quenching of
reaction intermediates of the solid state chemical heating
composition.
12. A heating device comprising: a heating chamber defining an
interior space for receiving and storing a substance to be heated;
a pocket adjacent to the heating chamber for receiving a modular
heater; and a modular heater comprising a housing comprising a
canister portion and a lid portion sealed together and defining an
exterior shape of the heater and a sealed interior space, the
modular heater further comprising a solid state chemical heating
composition and an activation mechanism disposed within the sealed
interior space, the modular heater disposed within the pocket;
wherein the actuation of activation mechanism generates sufficient
thermal energy to initiate a chemical reaction of the solid state
chemical heating composition.
13. The heater of claim 12, wherein the composition is comprised of
a fuel component, a solid oxidizer, and a thermal diluent.
14. The heating device of claim 12, wherein the pocket includes a
retaining groove to retain the modular heater within the
pocket.
15. The heating device of claim 14, wherein the modular heater
includes a ridge that correspondingly mates with the retaining
groove to secure the modular heater to heating device.
16. The heating device of claim 14, wherein the pocket and the
heater each have an annular-shaped periphery, and wherein the
retaining groove is an annular groove about the periphery of the
pocket and the ridge is an annular ridge about the periphery of the
heater.
17. The heating device of claim 14, wherein the heater includes one
or more protrusions that snap-fit into the retaining groove to
secure the heater to the heating device.
18. The device of claim 12, further comprising a retaining ridge at
a bottom of the pocket wherein the heater is secured to the heating
device by inserting the heating device into the pocket to engage
the retaining ridge.
19. The heating device of claim 12, wherein the pocket includes a
threaded surface.
20. The heating device of claim 19, wherein the heater includes a
threaded surface that is configured to correspondingly engage the
threaded surface of the pocket for securing the heater to the
heating device.
21. The heating device of claim 12, further comprising an adhesive
for securing the heater to the heating device.
22. The heating device of claim 12, further comprising an external
insulation layer, wherein the heater is secured to the insulation
layer using an adhesive and wherein the heater is inserted into the
pocket and the insulation layer is secured to the heating device
using an adhesive.
23. The heating device of claim 12, wherein heater comprises a band
having a diameter larger than the diameter of the heater and sized
for an interference fit into the pocket to secure the heater to the
heating device.
24. A heater for use as a source of heating a substance contained
in a heating device, the heater comprising: a housing defining an
exterior shape of the heater and an interior space, the housing
comprising a canister portion and a lid portion; a solid state
chemical heating composition disposed within the housing; and an
activation mechanism capable of communication with the composition
and having an actuator and disposed within the housing such that
the actuator is actuable from outside of the heating device when
heater is coupled to the heating device; a mechanism to
automatically shut down the oxidation of a solid state heating
composition when a pre-determined threshold temperature is reached
within the heater by the reaction of the solid state chemical
heating composition; wherein the canister and the lid of housing
are sealed together.
25. The heater of claim 24 wherein the lid portion is flexible.
26. The heater of claim 25 wherein the actuator is disposed
adjacent to the lid portion and is actuable by flexing the lid
portion.
27. The heater of claim 26 wherein the heater further includes a
flexible insulating layer between the solid state chemical heating
composition and the lid portion.
28. The heater of claim 26, wherein the composition is comprised of
a first fuel component, a second fuel component, a solid oxidizer,
and a thermal diluents.
29. The heater of claim 26, wherein the activation mechanism
comprises a piston, a blister pouch containing a first reaction
initiation material, and a pellet comprising a second reaction
initiation material and in communication with the solid state
chemical heating composition; the piston, blister pouch and pellet
being arranged within the heater such that when the lid portion is
depressed, the piston is depressed and ruptures the blister pouch,
thereby allowing the first reaction initiation material to contact
the pellet and initiate a chemical reaction between the first
reaction initiation material and the second reaction initiation
material that generates sufficient thermal energy to initiate
reaction of the solid state chemical heating composition.
30. The heater of claim 29, wherein the pellet further contains
fibrous particulates to promote wicking and rapid absorption of
first reaction initiation material.
31. The heater of claim 24, wherein the mechanism comprises an
intumescent material coated on an interior surface of the
heater.
32. The heater of claim 24, wherein the mechanism comprises an
intumescent material incorporated into the solid state chemical
heating composition.
33. The heater of claim 24, wherein the mechanism comprises a flame
retardant incorporated into the heater to slow the reaction of the
solid state chemical heating composition by gas phase quenching of
reaction intermediates of the solid state chemical heating
composition.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This non-provisional patent application is a Continuation of
U.S. application Ser. No. 13/177,502, filed on Jul. 6, 2011, which
claims priority to U.S. Provisional Patent Application No.
61/361,909, filed on Jul. 6, 2010, entitled "PACKAGE HEATING DEVICE
AND CHEMICAL COMPOSITIONS FOR USE THEREWITH", the entire contents
of each of which are hereby incorporated herein by reference in
their entirety.
TECHNICAL FIELD
[0002] This disclosure relates to precisely controlled exothermic
solid state reaction compositions and incorporation of those
compositions into a heating device for various applications such as
heating of prepared foods or beverages in their containers.
BACKGROUND OF THE INVENTION
[0003] Situations arise in which it would be convenient to have a
distributed means of providing heat in circumstances where heating
appliances are not available. For example, producers of prepared
foods have indicated that there could be significant market
potential for self-heating food packaging (SHFP) systems that could
heat prepared foods in their containers to serving temperature,
simply, safely, and efficiently.
[0004] For a mass consumer SHFP product, safety is paramount and
should be inherent; preferably there should be no exposure of users
to extreme temperatures, no fire, and no smoke or fumes under
anticipated use and abuse conditions. Practical considerations
mandate that any system be reasonably compact and lightweight with
respect to the food to be heated. Thus, the system should have a
good specific energy and high thermal efficiency. The system must
also be capable of extended storage without significant loss of
function or accidental activation of the heater. There should be
some simple means of activating the heater, after which the
required heat load should be delivered efficiently within a
specified time period or about one to four minutes. Operation must
be very reliable with low failure rates in millions of units of
production. For a single use food application, material components
should be food-safe, low-cost, environmentally friendly and
recyclable.
[0005] The only SHFP technology currently in the general consumer
market uses an onboard system for mixing separated compartments of
quicklime and water, yielding an exothermic heat of solution. These
products are bulky (literally doubling package size and weight),
complex, unreliable, costly, and have achieved very low market
penetration. There have also been reported instances of the heater
solution leaking and coming into contact with food or
consumers.
[0006] An exothermic reaction in which the component reactants
could be premixed yet be inert until such time as the user
initiates the reaction would be beneficial in terms of providing
for a simpler, more compact, and low cost package design. A solid
state reaction system could offer advantage over wet chemical
systems since solid systems will be less prone to spill or
leak.
[0007] While various solid state reactions can be considered, one
exemplary solid state reaction is appropriately moderated thermite
reactions. Thermites are a class of exothermic solid-state
reactions in which a metal fuel reacts with an oxide to form the
more thermodynamically stable metal oxide and the elemental form of
the original oxide. Thermites are formulated as a mechanical mix of
the reactant powders in the desired stoichiometric ratio. The
powders may be compressed into a unitary mass. These compact
reactions generate substantial thermal energy. However, thermite
reactions typically require high activation energy and thus
thermite reagent compositions can be formulated to be quite stable
against inadvertent initiation due to electrostatic shock or
mechanical impact. This generally inert character is an advantage
in storage and transportation. Solid state thermite reaction
formulations may also be formulated to yield precisely moderated
reaction characteristics with a controlled solid flame front speed
of less than 1 mm per second. Such moderated thermite formulations
have negligible gas reaction products and could be readily
integrated into heating device to achieve safe and efficient
heating of the contents of a container within about one to four
minutes.
[0008] Given certain preferred characteristics, other non-thermite
kinetically moderated solid state reaction systems, such as
moderated reaction compositions of iron powder fuel mixed with a
strong oxidizer, are also suitable for self-heating applications.
Preferred reaction systems would be comprised of premixed solid
state reactants with high heats of reaction so as to yield compact
high energy content devices that are inert and stable until
deliberately activated.
[0009] Further, although once activated the energy-releasing
chemical reaction may produce reaction intermediates in gas or
liquid form, it would be preferable that the principal final
products of the solid state reaction composition be solid
materials, so that there is not undesirable volume expansion or
pressure generation. Such solid state reaction systems, which would
generate negligible gas reaction products, would also be amenable
to being hermetically sealed into heating devices so as to fully
contain any emissions, smoke, or odors that do occur, if a facile
means of activating the sealed heating device can be provided.
[0010] The heaters that incorporate the solid state reaction system
should be easily integrated into heating devices that provide for
thermal product safety under anticipated use and inadvertent misuse
by consumers.
SUMMARY OF THE INVENTION
[0011] In addition to the chemical composition aspects, package
heating device and related aspects are provided.
[0012] According to a particular aspect, a heating device is
provided comprising a heating chamber defining an interior space
for receiving and storing a substance to be heated, a reaction
chamber disposed within the heating chamber, a solid state reaction
composition disposed within the reaction chamber such that it is
physically isolated from and in thermal communication with the
interior space of the heating chamber, and an activation mechanism.
The activation mechanism is in communication with the composition
disposed within the reaction chamber and the reaction composition
is inert until the activation mechanism is actuated.
[0013] According to another aspect, an activation mechanism is
provided for a heater containing a solid state chemical
composition. The activation mechanism comprises an actuator having
a user interface portion and an actuation portion. The actuation
portion carries a reaction initiation material that, when assembled
with the heater, is capable of initiating a chemical reaction in
the chemical composition when the actuation portion is actuated by
a user.
[0014] According to yet another aspect, a heater is provided for
use as a source of heat to heat a substance in a heating device.
The heater comprises a housing defining an exterior shape of the
heater and an interior space, a solid state chemical heating
composition disposed within the interior space, and an activation
mechanism in communication with the composition and having an
actuator disposed within the housing such that the actuator is
actuable exteriorly from the housing. The heater may be
incorporated into the heating device, or may be modular and
removably coupled to heating device. The heater can also be fully
sealed for emission-free operation, as well as to assure a
controlled internal environment and to promote stability during
storage.
[0015] According to yet another aspect, various passive and active
thermal controls based on physical or chemical responses of
materials to temperature and appropriate to important use
conditions for heating device are provided.
[0016] Other aspects will be apparent to those of ordinary skill in
the art.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] To understand the present invention, it will now be
described by way of example, with reference to the accompanying
drawings in which:
[0018] FIG. 1 is a perspective view of a particular embodiment of a
modular heater;
[0019] FIG. 2 is an exploded assembly view of the modular heater
depicted in FIG. 1;
[0020] FIG. 3A is a perspective breakaway view of the modular
heater of FIG. 1 having the lid, inert material layer, and
activation button removed;
[0021] FIG. 3B is a perspective breakaway view of an alternate
embodiment of the modular heater of FIG. 1 that does not utilize a
reaction regulator element, the view of the embodiment shown
without the lid and inert material layer;
[0022] FIG. 4 is a cross-sectional view of another embodiment of a
modular heater;
[0023] FIG. 5 is a perspective view of an embodiment of a fully
sealed modular heater;
[0024] FIG. 6 is a perspective cross-sectional view of the modular
heater embodiment in FIG. 5;
[0025] FIG. 7 is a cross-sectional view of another embodiment of a
heater disposed within a container having a flexible lid and a
flexible insulation layer for depressing activation mechanism and
forcing a starter pellet to crush or puncture a crucible filled
with reaction initiation material;
[0026] FIG. 8 is a cross-sectional view of another embodiment of a
heater disposed within a container having a flexible lid for
depressing activation mechanism causing a syringe piston to expel
reaction initiation material to be dispensed onto the starter
pellet;
[0027] FIG. 9 is a perspective view of another embodiment of a
modular heater utilizing a resistive heating activation
assembly;
[0028] FIG. 10 is an exploded assembly view of a particular
embodiment of a package heating device in the form of a beverage
cup having a pocket to accommodate a modular heater;
[0029] FIG. 11 is an exploded assembly view of a particular
embodiment of an end portion of a package heating device having a
pocket to accommodate a modular heater and a safety seal;
[0030] FIG. 12 is a perspective view of another embodiment of a
modular heater;
[0031] FIG. 13 is an exploded assembly view of a particular
embodiment of an end portion of a package heating device having a
pocket to accommodate a modular heater embodiment such as those
shown in FIGS. 1, 4, 5, and 6;
[0032] FIG. 14A is a plan view of a container portion in a form of
a can end having a pocket formed therein having protrusions to
facilitate retention of a modular heater therein;
[0033] FIG. 14B is a cross-sectional assembly view of the container
portion of FIG. 14A and a modular heater;
[0034] FIG. 15 is a perspective assembly view of a container
portion in a form of a can end having a pocket formed therein
having protrusions to facilitate retention of a modular heater
therein, wherein the modular heater includes a detent;
[0035] FIG. 16 is a perspective assembly view of a container
portion in a form of a can end having a pocket formed therein
having a thread arrangement that correspondingly engages a thread
arrangement on the heater;
[0036] FIG. 17 is a cross-sectional assembly view of a container
portion in a form of a can end having an opening formed therein for
receiving a heater having a band for engaging with container;
[0037] FIG. 18A is a cross-sectional assembly view of a container
portion in a form of a can end having an opening formed therein for
receiving a heater and adhesive for securing the heater to the
container;
[0038] FIG. 18B is a cross-sectional assembly view of a container
portion in a form of a can end having a pocket formed therein for
receiving a heater and an external bottom insulation layer with
thermal adhesive for securing heater to the container;
[0039] FIG. 19A is a cross-sectional assembly view of a container
portion in a form of a can end having a pocket formed therein
having a groove that correspondingly engages a ridge on the
heater;
[0040] FIG. 19B is a cross-sectional assembly view of an
alternative heater with knobs that correspondingly engage with
groove of container in FIG. 19A;
[0041] FIG. 19C is a cross-sectional assembly view of a container
portion in a form of a can end having a pocket formed therein
having a ridge that correspondingly engages the heater;
[0042] FIG. 20A is a cross-sectional view of a heater disposed
within a pocket of a container portion, wherein a flexible
insulating layer is disposed over the activation mechanism and
heater;
[0043] FIG. 20B is a cross-sectional view of a heater disposed
within a pocket of a container portion, wherein an insulative cap
is disposed over the activation mechanism and heater;
[0044] FIG. 21A is a top view of an alternative embodiment of a
heater package design in accordance with the present invention;
[0045] FIG. 21B is a perspective view of the embodiment of FIG.
21A;
[0046] FIG. 21C is a side view of the embodiment of FIG. 21A.
[0047] FIG. 21D is a side cross-sectional view of the embodiment of
FIG. 21A; and
[0048] FIG. 21E is a perspective cross-sectional view of an
alternative embodiment of a heater package design.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0049] The description that follows describes, illustrates and
exemplifies one or more particular embodiments of the present
invention in accordance with its principles. This description is
not provided to limit the invention to the embodiments described
herein, but rather to explain and teach the principles of the
invention in such a way to enable one of ordinary skill in the art
to understand these principles and, with that understanding, be
able to apply them to practice not only the embodiments described
herein, but also other embodiments that may come to mind in
accordance with these principles. The scope of the present
invention is intended to cover all such embodiments that may fall
within the scope of the appended claims, either literally or under
the doctrine of equivalents.
[0050] It should be noted that in the description and drawings,
like or substantially similar elements may be labeled with the same
reference numerals. However, sometimes these elements may be
labeled with differing numbers, such as, for example, in cases
where such labeling facilitates a more clear description.
Additionally, the drawings set forth herein are not necessarily
drawn to scale, and in some instances proportions may have been
exaggerated to more clearly depict certain features. Such labeling
and drawing practices do not necessarily implicate an underlying
substantive purpose. The present specification is intended to be
taken as a whole and interpreted in accordance with the principles
of the present invention as taught herein and understood to one of
ordinary skill in the art.
[0051] Food safety and cost are two primary considerations in the
selection of potential materials for use in the illustrative
embodiments described herein. The reaction systems described in
this application involve only abundant, low-cost, food-safe
materials and are therefore in this regard good candidates for
SHFP. However, those of ordinary skill in the art will understand
that many different materials could be selected without departing
from the novel scope of the present invention.
[0052] One solid state reaction system that may be used in the
present invention is thermite reactions wherein the reaction of a
metal fuel with one or more oxides to form the more
thermodynamically stable metal oxide and the elemental form of the
original oxide(s) is appropriately moderated to give a combustion
wave speed of much less than 1 m s.sup.-1. Factors that can be
altered to adjust the reaction rate and combustion temperature of
solid state systems include: particle size of reactants,
composition, diluent (inert) additives, precombustion density,
ambient pressure and temperature and physical and chemical
stability of reactants.
[0053] The principles of the present invention may also be applied
by using alternative solid state reaction systems for generation of
thermal energy. One potential advantage of alternative reaction
systems over thermites is a lower activation energy such that
reaction can be sustained at lower temperatures. One such reaction
system is the complete reaction between the fuel iron powder and an
oxidizer which is a chlorate of sodium or potassium in
stoichiometric balance. This reaction system yields the generally
benign products iron oxide and sodium chloride, and releases a high
specific energy content of 3.98 kJ g.sup.-1. The iron/sodium
chlorate reaction has excellent shelf life stability prior to
activation. These properties make it a preferred solid state
reaction system for use with the heating application of the present
invention.
[0054] A common commercial use of the iron/sodium chlorate chemical
reaction is in chemical oxygen generators (often referred to as
"oxygen candles") that are used in commercial aircraft to provide
emergency oxygen to passengers in the event of reduced cabin
pressure. In oxygen candle applications, the molar or mass ratio of
iron to chlorate is deliberately kept very low (2 to 6 weight
percent). In such formulations, all of the oxygen will not be
consumed in oxidation of the iron but rather when the mixture is
ignited; a smoldering reaction releases about 6.5 man-hours of
oxygen per kilogram of the mixture at a steady rate, in addition to
sodium chloride and iron oxide byproducts.
[0055] Prior art oxygen candles are optimized for the most
efficient volumetric generation of oxygen by carefully balancing
iron oxidation by chlorate to generate heat just sufficient to
sustain endothermic decomposition of the excess chlorate. Other
functional additives may be added to the formulation, but always in
minimal quantities to maximize the volumetric oxygen content of the
system.
[0056] An iron-chlorate reaction may be used for an enclosed heat
generation system as contemplated herein by modifying the prior art
oxygen candle. For use with the present invention, the oxygen,
rather than being emitted externally to the device, is fully
reacted internally in the heating device to a solid oxide. One
means to accomplish the complete capture of oxygen is to adjust the
stoichiometry of the reaction mixture to include a second fuel
component (for example, more iron powder) that reacts with the
oxygen as it is generated.
[0057] Increasing the catalytic iron content of the reaction
mixture over that described in prior art oxygen candle technology
will significantly increase the rate of chemical reaction while
simultaneously increasing the thermal energy output per unit mass
of mixture; such conditions can lead to autocatalytic thermal
runaway. In order to provide appropriate moderation of the chemical
reaction temperature and rate, a significant portion of an inert
thermal diluent may be added into the reaction composition, as well
as other functional additives to improve the processing or
performance of the formulation.
[0058] It is generally desirable for the heating applications
contemplated herein to optimize heat generation with the minimal
net gas generation. Thus, the mass loading of iron fuel component
relative to the oxidizer chlorate in the composition is
substantially increased so that oxygen released is largely consumed
simultaneously. Other oxygen consuming materials may also be added.
When formulated in this way, substantially more heat will be
released as reactions proceed, and substantially more thermal
diluent is incorporated in the system relative to prior art
chlorate candles to moderate temperature to practically suitable
levels. Diluents may include inert oxides such as silicas,
aluminas, clays, or other. The particle sizes of the materials and
other reaction conditions are also formulated to provide for faster
reaction such that all the heat is released within about one to
four minutes rather than over extended periods of 10 minutes or
more.
[0059] Table 1 describes various moderated iron-chlorate reaction
compositions that may be used with the present invention. All of
the example formulations have stoichiometric ratios of iron fuel to
oxidizer of 1:1 or higher, as well as a high loading of an inert
thermal diluent (alumina). The iron fuel is preferably in the form
of a powder with particle sizes ranging from 3 to 40 microns and
the sodium chlorate is preferably finely milled prior to mixing and
compacting the formulations into a heater canister. Fuel to
oxidizer ratios of slightly greater than 1:1 are preferred for the
most efficient consumption of free oxygen, most preferred is a
ratio of about 1.1 to 1. All of the example formulations have
negligible free gas generations as well as solid flame front speeds
of less than 1 mm per second. This reaction rate constant
corresponds to a heating time of about one to four minutes and a
delivered energy content in excess of 0.8 to 1.2 kJ g.sup.-1 of the
reaction mixture when incorporated into the heating device and
apparatus of the current invention.
TABLE-US-00001 TABLE 1 Examples of Moderated Iron-Chlorate Reaction
Compositions I. II. III. IV. Component wt. % wt. % wt. % wt. %
NaCIO.sub.3 13.9% 13.3% 12.7% 27.2% Fe 14.6% 15.3% 16.0% 31.4%
BaO.sub.2 1.3% 1.2% 1.1% 1.2% Al.sub.2O.sub.3 70.0% 70.0% 70.0%
40.0% Ceramic Fibers 0.2% 0.2% 0.2% 0.2% Fuel to oxidizer ratio 1:1
1.1:1 1.2:1 1.1:1
[0060] As an alternative to directly incorporating the full
complement of solid fuel into the reaction mixture, additional
oxygen-reactive fuel mass such as porous iron could be disposed
adjacent to a sub-stoichiometric iron-chlorate mixture inside the
heater such that all of the oxygen released by the chlorate is
still reacted into solid oxide products and consumed internally. In
this alternative, there is no net production of gas to cause
pressure build up or emissions from the device.
[0061] The iron chlorate reaction is not a true thermite system.
However, similar to the moderated thermite compositions described
previously, it includes a powdered metal fuel, a strong oxidizer,
and a thermal diluent. While the foregoing discussion describes
sodium chlorate, potassium and lithium chlorate, and sodium,
potassium and lithium perchlorates, or other inorganic chlorates,
perchlorates, or super-oxides can also be used to fully or
partially substitute. Similarly, solid fuel materials other than
iron that produce solid oxides may also be used.
[0062] The reaction kinetics may be more precisely adjusted by
using, for example, a mixture of sodium and potassium chlorates,
thus utilizing their distinctive thermal decomposition properties.
Other chlorates or oxidizing components may also be included in the
formulation. Other functional additives may also be used and are
considered within the scope of the invention. For example, barium
peroxide can be used to absorb free chlorine generated by
decomposition of the chlorate.
[0063] Preferred moderated solid state reaction systems for the
heating device of the present invention are amenable to inclusion
in heater structures that encapsulate the materials while
permitting efficient transfer of heat from the heater. A still
further aspect of the present invention is integration of a heater
comprised of a solid state chemical composition and an activation
mechanism into the packaging of a food product to be heated by a
consumer. An appropriate design of package can be used in
conjunction with the moderated composite fuel formulation to
provide for ease of use and additional consumer safety.
[0064] Increased weight and volume of packaging relative to the net
food content translates to higher shipping costs and shelf space
requirements. Therefore, in order to keep packaging overhead low, a
compact SHFP heater is preferred. However, a compact geometry means
less surface area is available for heat transfer, which is an
important consideration where the food to be heated is not readily
stirred to provide convective heat transfer. Conductive heat
transfer from a small heater to a larger mass of solid or
non-stirrable food material will provide inefficient and uneven
heating.
[0065] In order to overcome these limitations, the heater as
contemplated by the present invention may be implemented so that
the heat it generates raises steam that distributes throughout the
package interior and transfers sensible and latent heat (via
condensation) to the food. For this purpose, a small quantity of
water is maintained in contact with the outer surface of the
heater. For example, a heater structure could be in contact with a
water absorbant material or a liquid water reservoir in the base of
the package. The combustion characteristics of the heater are
designed so that in operation, the exterior surface of the heater
maintains a temperature sufficient to vaporize water to steam.
[0066] The principles of the invention can be applied to provide a
modular heater, such as one embodiment of a modular heater 100 as
shown in FIG. 1, which can be provided in numerous forms and
incorporated into a variety of devices, containers, or the like to
provide a source of heat. In the embodiment shown in FIG. 1, the
modular heater 100 has a form in a general cylinder or disc shape.
While other shapes are contemplated, the general cylinder or disc
shape is particularly suitable for manufacturing as well as
integration into container and packaging forms generally available
in the food and beverage industry, such as, for example, soup cans,
beverage containers, "instant" or "travel" style food container
forms, or the like. The heater 100 includes a housing 110 and an
activation mechanism 112, which provides activation of the heater
100 and initiates production of heat by a chemical reaction in
accordance with the principles of the present invention.
[0067] One embodiment of a heater is shown in the exploded assembly
view of FIG. 1, the housing 110 of the heater 100 preferably
includes a lid 114 and a canister portion 116, which define an
exterior shape of the heater 100 and an interior space 118. In this
particular embodiment, a reaction regulator element 120 is disposed
within the canister portion 116 such that when the canister portion
116 is filled with a solid state chemical heating composition 122,
as shown in FIG. 3A, the reaction regulator element 120 is embedded
within the composition 122 to define a reaction path. As shown in
FIGS. 2 and 3A, the reaction regulator element 120 has a
spiral-like shape defining a spiral-like reaction path. However,
other geometries can be employed as well to define various path
shapes, lengths and thicknesses, and are contemplated in accordance
with the principles of the invention. In addition to adjustment of
variables within the composition, such as for example, particle
shape and size, composition ratios, etc., the reaction regulator
element 120 can be optimized to impart desired regulation and
control over the reaction or bum path and rate of reaction, and
hence, bum time, within the composition 122. For example, the
spiral-like shape of the reaction regulator element 120 has been
shown to provide a consistent and more regular burn pattern
emanating from the center of the disc-like shape to which the
composition 122 has been formed. In a preferred embodiment, the
reaction regulator element 120 is made of a thin metal strip, such
as steel, however, numerous other materials may be employed that
are suitable to effectively perform the function of defining a
reaction path with the given composition.
[0068] While embodiments incorporating the reaction regulator
element 120 may be desirable in certain applications, it is to be
understood that it may be desirable in some applications to forego
use of the reaction regulator element 120, particularly in cost
sensitive applications. Furthermore, as already noted above, burn
rates and paths, and heat generation rates may be optimized via
adjustment of variables within the composition, such as for
example, particle shape and size, composition ratios, etc. In such
embodiments, the reaction composition 122 is disposed within the
canister portion 116 as shown in FIG. 3B, wherein the reaction
would initiate generally in a central portion of the reaction
composition 122 and propagate generally radially outward therefrom.
It should be understood that the embodiment illustrated in FIG. 3B
may be employed in connection with any of the descriptions herein
with respect to embodiments incorporating the reaction regulator
element 120 (such as that illustrated in FIG. 3A), and accordingly
should not be excluded from consideration in connection with such
descriptions.
[0069] FIG. 4 shows another preferred embodiment of a heater 100
with a solid lid 140 having a central opening 142 through which an
actuator in the form of a plunger 144 is pushed by the user. The
actuator is part of an activation mechanism, which may include
bearing surfaces 156 to guide the plunger or limit its travel. To
effect activation of the solid reaction mixture 146, the plunger
144 coupled to the canister 150 is capable of mechanical movement
into the interior. The activation mechanism includes a blister 160
formed of foil or other material pierceable by plunger 144. The
blister 160 is partially filled with a small quantity of a starter
fluid that will rupture under applied pressure such that the fluid
is expelled onto an absorbant material 162 and then transmitted to
a formed starter pellet 164 comprised of a chemical mixture that
will react with the fluid contained in the blister 160. The starter
pellet 164 is embedded into the surface of the solid state reaction
mixture 146. The starter fluid and pellet 164 together constitute a
spontaneous highly exothermic chemical reaction couple that
generates sufficient thermal energy to initiate the main solid
state reaction. The components just described act together to
effectively act as a push-button activation mechanism such that
when the plunger 144 is pressed by a user, it initiates a sequence
leading to a precursor chemical reaction between the fluid expelled
from the blister 160 and the chemical mixture in the pellet 164
that generates intense localized heat that initiates reaction of
the solid state reaction mixture 146 and heat generation. An
interior structural component 180 may be used to maintain the
position of the blister 160 in the center of the heater 100 and in
contact with the starter pellet 164, while also creating an air gap
around the pellet 164 that facilitates dissipation of the gaseous
products of the starting reaction. For greatest reliability, some
means of assuring that rupture of the blister 160 occurs in the
center of its surface in contact with the absorbant 162 is
preferentially included. For example, a ball bearing 190,
preferably about 1-2 mm in diameter, may be included in the
interior of the blister 160 to act as a centrally directed force
concentrator.
[0070] For certain embodiments of the heater device, it may be
acceptable or desirable to provide a passage or vent to allow any
gas that may result from the chemical reaction to escape from the
heater housing. In such embodiments, a gas "valve" or vent can be
formed into the housing. In the embodiment shown in FIG. 4, the
gaps between the central opening 142 in the solid lid 140 and the
plunger 144 effectively constitute such a vent opening, as may also
be realized by any unsealed gaps between the lid 140 and the
canister 150. Prior to activation, the gap between the plunger 144
and the lid 140 could be sealed by an adhesive that releases when
sufficient pushing force is applied, but this seal may be broken by
the relative motion between the plunger 144 and the lid 140 that
transmits operation of the activator mechanism into the interior of
the heater.
[0071] Alternatively, the principles of the invention can also be
applied to provide a modular heater which is fully sealed, such as
the embodiment of a modular heater 200 shown in FIG. 5, which can
be provided in numerous forms and incorporated into a variety of
devices, containers, or the like to provide a source of heat. A
number of benefits are provided when the heater is fully sealed.
For example, if the reaction components or any of the internal
components of the heater are potentially affected by changes in
external ambient factors such as humidity, complete sealing of the
heater, such as through hermetic sealing, can be used to assure a
controlled internal environment and promote stability during
storage. This may be particularly beneficial if the heater must
pass through high temperatures and pressures in food sterilization
processing. For heater use by consumers, and particularly in
association with food heating applications, it is beneficial to
assure that chemical components of the heaters are fully sealed
against potential contact with the user or food. A fully sealed
heater can potentially be operated immersed in the substance to be
heated without contamination concerns.
[0072] Sealing of the heater can also eliminate smoke, fume, or
odor emissions from the operating heater after activation for a
more favorable user experience. As described previously, in order
to facilitate encapsulation into a sealed heater, the solid state
reaction systems of this invention are formulated to produce little
or no gaseous reaction products. To further reduce potential gas
generation in the device and facilitate sealing, the reaction
materials may also be dried during processing to drive off water
and other volatiles. Noncombustible materials of construction with
low tendency toward out-gassing may also be preferred for other
internal components of the heater.
[0073] In accomplishing sealing of the heater, a means to activate
the solid state reaction in a simple but reliably effective manner
must be accomplished. The solid fuel should not be prone to
inadvertent activation, yet the heater should incorporate a simple
means of activating the reactive material in the heater at the
desired time of use. FIGS. 5 and 6 show an embodiment of heating
device that achieves the simultaneous objectives of a sealed heater
that can easily be activated. FIG. 5 shows a perspective view of
the heater 200, which composes a canister 210 and a flexible lid
220.
[0074] In FIG. 6, another preferred embodiment of a heater 200,
canister 210 contains a layer of the solid state reaction mixture
230. The activation mechanism preferably comprises the following
components: (1) a flexible lid 220 coupled to the canister 210 that
is capable of mechanical deflection into the interior, (2) a piston
240 positioned adjacent to the interior surface of the flexible lid
220, (3) a blister 250 formed of foil or other material rupturable
by piston 240, the blister 250 positioned below piston 240 and
being partially filled with a small quantity of a reaction
initiation material or "starter fluid" that will rupture under
applied pressure such that the fluid is expelled onto (4) a formed
starter pellet 260 comprised of a chemical mixture that will react
with the fluid contained in the blister 250, the starter pellet 260
embedded into the surface of the solid state reaction mixture 230.
It should be understood, however, that various modifications,
substitutions or omissions may be employed without departing from
the scope and function of the present invention. The starter fluid
and pellet 260 together constitute a spontaneous highly exothermic
chemical reaction couple that generates sufficient thermal energy
to initiate the main solid state reaction. All of the components
described act together to effectively act as a push-button
activation mechanism such that when the center of the lid 220 is
pressed by a user, it initiates a sequence leading to a precursor
chemical reaction between the fluid expelled from the blister 250
and the chemical mixture in the pellet 260 that generates intense
localized heat that initiates reaction of the solid state reaction
mix 230 and heat generation. Heater 200 may also comprise a thermal
resistance layer 270. All of the materials and components disclosed
herein, as well as the simple, robust construction of the heater
200, provide for low cost, high volume manufacture.
[0075] One preferred exothermic starter reaction couple which can
be configured to reliably generate very high temperatures with
minute quantities of reagents for use in the activation mechanism
is potassium permanganate (or other strong oxidizer) in the starter
pellet 260 in conjunction with a glycerin, glycerol, glycol or
other liquid polyalcohol as the starter fluid. In a preferred
embodiment, approximately 2-20 .mu.l, and more preferably
approximately 10 .mu.l, of fluid is encapsulated in the blister
250. In the case of glycol and other similar compounds, such
amounts minimize carbon dioxide gas generation from the initiation
reaction and hence pressure build-up in the heater 200.
[0076] A preferred embodiment of blister 250 is constructed to
provide for stable retention of the starter fluid, and consists of
a formed pocket in a foil laminate (or other similar material
rupturable by piston 240) that, after filling with starter fluid,
is sealed with an adherent thin foil (or other suitable material)
seal. The foil seal is configured to be the surface that ruptures
under applied force by piston 240 to release the started fluid. The
foil seal may be laser scribed to reduce the force required for it
to rupture. For greatest reliability, the majority of the starter
fluid in the blister 250 should be delivered in a reproducible
manner onto the center of the starter pellet 260. Alternatively,
small mechanical piercing elements that are internal or external to
the blister 250 may also be incorporated into the activator
mechanism in order to facilitate uniform, targeted fluid delivery
characteristics.
[0077] The permanganate starter pellet 260 may additionally contain
small additions of solid fuel materials such as metal powders to
increase the heating effect. In order to increase the reliability
of the starting reaction, the starter pellet 260 may also contain a
few percent by weight of fibrous particulates such as fiberglass or
ceramic fibers to promote wicking and rapid absorption of the
starting fluid. In order to further increase reliability of the
starting reaction, particularly such that the heater can be
initiated in any orientation, a thin layer of an absorbent material
such as cellulose, filter paper, or fiberglass mat may be
interposed between the blister 250 and the starter pellet 260 to
capture, and then transmit to the pellet 260, the starting fluid
expelled from the blister 250.
[0078] The continuous, impermeable, flexible metal diaphragm
structure of the flexible lid 220 is similar to the pop-up
indicators in food jar lids that show whether the vacuum seal has
been broken, but may have additional functionality specific to the
heater 200. The force required to deflect the flexible lid 220 can
be calibrated to be sufficiently low for finger pushing operation
by a typical user but not so low as to lead to inadvertent
activation of the heater 200; thus the force required may be for
example in the range of two to five pounds. The flexible lid 220 is
preferably engineered to give a specific reproducible displacement
of its center so as to always cause the proper compaction of the
blister 250. When appropriate force is applied to the center of the
lid 220, it pushes the piston 240 through a deflection distance
(approximately 2 mm in a preferred embodiment) and effects the
force needed to puncture the blister 250 and expel the starting
fluid onto the pellet 260. In a preferred embodiment, the piston
260 may be a stamped metal part affixed to the interior surface of
the flexible lid 220; other structures which may be suitably held
in place would also be effective. The piston 260 has low thermal
mass such that it does not draw substantial heat energy from the
activation region.
[0079] For most effective heat transfer when installed in the
heating device, the closed end of the canister 210 adjacent to the
solid state reaction mixture 230 will be oriented so as to be
nearest to the vessel or substance being heated. Materials and
structures that resist the flow of heat preferentially occupy the
interior space of the heater 200 between the solid state reaction
mixture 230 and the activation mechanism. In one embodiment, an
interior band of space 275 may be formed of one or more walls or
baffles, insulating air gaps, or layers of insulating materials.
Band preferably spans from the top surface of the reaction mixture
230 to the bottom surface of lid 220. A thermal resistance layer
270 may also be incorporated, and is preferably adjacent to the
flexible lid 220 and is preferably a compressible structure, such
as a compressible fiberglass layer or ceramic mat, or otherwise
constructed such that it does not interfere with actuation.
[0080] Prior to activation, the flexible lid 220 is effectively at
rest in a stable "popped up" state. In a preferred embodiment, the
flexible lid 220 may be engineered so that once pushed it snaps
down and comes to rest in a stable "popped down" state, thus
providing an audible or tactile indication that the heater 200 has
been activated. In the un-activated state, the moveable central
portion of the flexible lid 220 may be somewhat recessed from the
outer edges so that if several heaters 200 are stacked, the
flexible lid 220 is not inadvertently pushed. The mechanical design
of the flexible lid 220 can be arranged such that the full
operational translation of its center is only given by a centrally
applied force yet not under a generally applied change in ambient
pressure. This feature would permit the installed heater 200 to be
passed through a pressurized retort or autoclave used to sterilize
packaged foods without being activated. In an alternative
embodiment (not shown), the flexible actuator panel of the sealed
heater could be configured for location off-center or in a side
wall of the canister.
[0081] Any of a number of known methods for sealing lids onto metal
containers could be used to seal flexible lid 220 to canister 210.
One appropriate sealing method is hermetic sealing. Referring again
to FIG. 4, hermetic sealing can be accomplished by first firmly
seating the flexible lid 220 into place on the canister 210 and
then applying a crimping force to form the edge of the canister 210
over the lid 220, bringing the two metal surfaces into close
contact. An airtight seal is achieved by applying a thin layer of a
high temperature sealant in the joint area prior to crimping.
Alternatively, the lid 220 and canister 210 may be provided with
formed edges that permit sealing using conventional single or
double seaming methods as is done with food cans.
[0082] In another embodiment of a modular heater, shown in FIG. 7,
the solid state reaction may be activated by a user pushing on a
flexible lid 310. When the lid 310 is pushed downward, a flexible
insulation layer 320, such as a ceramic or fiberglass mat,
depresses a pusher 330 and forces it to crush or puncture a pellet
340 filled with a chemical mixture. A suitably firm pellet 340 or a
puncturing boss (not shown) on the pellet 340 would puncture a foil
(or other material) lid which forms a lid on blister 350. The
activation mechanism may be recessed in an insulation layer 320,
the insulation layer 320 insulating against heat conduction through
the flexible lid 310. An inert spacer 360 may also be provided to
allow movement of pusher 330 toward pellet 340.
[0083] Another embodiment of a modular heater 400 is shown in FIG.
8. In this embodiment, activation mechanism is comprised of a
syringe piston 420 which may be actuated by a user pushing on a
flexible lid 410. When the lid 410 is pushed toward the solid state
chemical reaction mixture 430, the syringe piston 420 is forced
downward to expel reaction initiation material contained in chamber
440 to be dispensed onto a starter pellet 450, thus initiating the
solid state chemical reaction. An insulation layer 460 may be
provided to insulate against heat conduction through the flexible
lid 410.
[0084] The modular heater can make use of any number of activation
mechanisms contemplated herein. In another exemplary embodiment
illustrated in FIG. 9, a heater 500 is provided utilizing a
resistive heating activation concept. In accordance with this
concept, the heater includes a housing 502, which further includes
a lid 504 and a container portion 506, together generally defining
an exterior shape of the heater 500 and an interior portion for
housing chemical heating composition as previously described. In
this embodiment, heater 500 includes a pair of terminals 508 in
communication with a resistive heating component 510, which is in
contact with the composition, and preferably embedded therein to
ensure proper activation. While capable of being utilized in any
configuration contemplated herein, this arrangement is particularly
suitable for use in modular applications where the heater 500 is
provided for use in connection with reusable heating devices.
Although not shown, application of this embodiment includes a power
source, such as a battery, which provides adequate voltage to allow
the resistive heating component 510 to achieve appropriate
temperatures. In a particular embodiment, a starter composition may
be disposed around the resistive heating component to help initiate
the contemplated chemical reaction within the chemical composition.
In other embodiments, a piezoelectric igniter may be utilized in a
similar configuration to that illustrated in FIG. 9.
[0085] A still further aspect of the present invention is
integration of a heater comprised of a solid state reaction
composition and an activation mechanism into the packaging of a
food product to be heated by a consumer. An appropriate design of
package can be used in conjunction with the moderated solid state
reaction composition to provide for ease of use and additional
consumer safety. The solid state reaction composition can be
integrated into a package in a way that provides for efficient
transfer of the heat generated to the material to be heated. To
illustrate this aspect of the invention, several illustrative
embodiments describing designs for incorporating solid fuel
compositions into self-heating food packaging follow.
[0086] A modular heater as described herein can be employed in a
variety of contexts, including but not limited to mass produced
consumer food and beverage containers. In such applications, the
heater must be installed at very high production rates, yet in such
a secure manner as to eliminate the potential for accidental
dislodgement during use. As illustrated in FIG. 10, a package
heating device 600 is provided with a beverage container 602 and a
heater 100. The beverage container 602 is formed with a pocket 604
to accommodate the heater 100. For ease of illustration, only the
beverage container 602 and the heater 100 are illustrated, with the
understanding that other components may be included as well, such
as, for example, a safety seal covering the actuator of the
activation mechanism and a product seal or other product packaging
requirements. The heater 100 may be configured to be press fit into
the pocket 604 during a manufacturing process. In other
embodiments, the heater 100 may be adhered or otherwise suitably
secured to the beverage container 602. The heater 100 may
alternatively be fully integrated with the beverage container 602.
In another alternative embodiment (not shown), a fully sealed
heater, such as that shown in FIGS. 5 and 6, may also be coupled to
beverage container 602.
[0087] FIG. 11 illustrates another exemplary package heating device
700, which is particularly suitable for canned food items, such as
soup or chili. In this embodiment, a container end 702 is provided
with a pocket 704 configured to accept the heater 100. The
container end 702 is designed to be formed onto a container
cylinder 706 (partially shown in phantom line) to form a bottom
portion of the heating device 700. Thus, the heater 100 is disposed
on the bottom of the heating device 700. A safety seal 708 is
preferably applied to the container end 700 to cover the heater 100
and thus, the actuator 130 of the activation mechanism 112 to
prevent accidental activation. With both embodiments, the heater
100 is designed such that it can be assembled to the food or
beverage packaging container at any point in the manufacturing
process, including before any autoclaving process, such as that
typically applied in canned food processes. Furthermore, the
container end 702 is designed such that it can be provided as a
sub-assembly already containing the heater 100 and safety seal 708.
In such an application, the container end sub-assembly can be
formed onto the container cylinder 706 without the need for further
assembly with respect to the heater 100. The heater 100 may
alternatively be fully integrated with the beverage container end
702. In another alternative embodiment (not shown), a fully sealed
heater, such as that shown in FIGS. 5 and 6, may also be coupled to
beverage container end 702.
[0088] Referring again to the embodiments of FIGS. 10 and 11, each
of the pockets are provided with at least one, and preferably a
plurality, of respective channels 680, 780 along a respective
sidewall 682, 782 of each of the pockets 604, 704. These channels
680, 780 provide a venting mechanism for air trapped between the
heater 100 and the pockets 604, 704 to escape and thereby prevent
expansion and pressure build during heating. Alternatively, scored
channels may be formed along the sidewalls of the modular heater
100 itself in order to provide the venting mechanism. The channels
680, 780 also prevent air lock during installation of the heater
100.
[0089] Although not shown in the drawings, any of the devices,
containers or packages may be configured with a reservoir in
communication with the heater and in communication with the
interior portion of the device, container or package that contains
the substance to be heated, wherein the reservoir holds an amount
of water that, upon activation of the heater, generates steam that
may be used in the heating and preparation of the substance. Such a
configuration would be particularly suitable for heating food items
such as, for example, rice and pasta.
[0090] As noted above, the heater 100 may be a modular element,
either configured to be fit into an associated pocket of a device,
container or package during a manufacturing process, or as an
addition to a reusable device, container or package. Mechanisms for
engagement between a modular heater and the container or package
include, but are not limited to, those shown in FIGS. 12 to 20.
[0091] One such additional embodiment of an exterior package
configuration for a heater is illustrated in FIG. 12 as a heater
800. In this particular embodiment, the heater 800 includes a
housing 810, which further includes a lid 812 and a container
portion 814, together generally defining an exterior shape of the
heater 800. As shown in FIG. 12, the container portion 814 includes
a retaining groove 816 for use in connection with a retaining
mechanism for assembly within a pocket of a container or package.
As shown in FIG. 13, an exemplary package heating device 900, which
is particularly suitable for canned food items, includes a
container end 902 with a pocket 904 configured to accept the heater
800. The container end 902 is designed to be formed onto a
container cylinder 906 (partially shown in phantom line) to form a
bottom portion of the heating device 900. As shown in FIG. 13, the
pocket 904 includes a retaining ridge 908 that correspondingly
mates with the retaining groove 816 of the heater 800 when
assembled. In such an arrangement, the retaining groove and the
retaining ridge can be dimensioned appropriately to provide a
desired fit. Preferably, in this particular embodiment, the
retaining mechanism will not allow disassembly without undue effort
or the use of special tools.
[0092] As shown in FIGS. 14-16, additional embodiments of retaining
the modular heater include a modified snap-fit arrangement, a
detent arrangement and a twist lock arrangement. Again, as
previously noted, other mechanisms known in the art are
contemplated as well. Referring to FIGS. 14A and B, a snap-fit
arrangement includes one or more protrusions 1002 formed in
connection with a pocket or receptacle 1004 on a container portion
1006, such as a can end of a can-type container. Other containers
or cans having pockets or receptacles are contemplated as well,
such as 2-piece or 3-piece can designs known in the canned food
industry that have been designed with such pocket or receptacle. In
a particular embodiment, one contiguous protrusion is disposed
around the periphery of the pocket. In another embodiment, two or
more protrusions are disposed around the periphery of the pocket.
In this particular embodiment, the protrusions 1002 are formed
adjacent an open end 1007 of the pocket so that the protrusion(s)
act to retain a modular heater 1008 within the pocket 1004 when
assembled. When the modular heater 1008 is fit into the pocket
1004, the protrusions 1002 either deform or cause deflection and
flexing of sidewall(s) 1010 of the pocket (or a combination of
deformation and flexing) to allow the modular heater 1008 to be
inserted and captured in the pocket 1004. Once assembled, the
protrusion(s) 1002 capture the modular heater 1008 and act to
prevent it from being removed from the pocket 1004.
[0093] In an embodiment utilizing a detent, such as that
illustrated in FIG. 15, a modular heater 1102 includes one or more
grooves or steps 1104 (depending on the geometry of the heater)
disposed annularly or peripherally (depending on the geometry of
the heater, package, or pocket) around heater 1102 designed to
capture at least a portion of the protrusions 1002 previously
described with respect to FIG. 14A. This embodiment is similar in
concept to that previously described and illustrated in FIG. 13,
one difference being that in this embodiment, the detent is
disposed adjacent the open end of the pocket so that the
protrusion(s) act to retain the modular heater within the pocket
when assembled. In a particular embodiment, the modular heater may
be configured with a geometry having a shoulder-type design in lieu
of a groove wherein the protrusion would capture the modular heater
by engaging the shoulder. In yet another embodiment, such as that
shown in FIG. 16, a modular heater 1202 may be assembled within a
pocket 1204 by utilizing a twist-lock arrangement, which may
comprise a threaded arrangement 1206, 1208 between the pocket and
the heater, or a combination of protrusions (not shown)
incorporated in both the pocket and the heater, wherein the
protrusions from the respective components would act upon each
other when the heater is disposed within the pocket and twisted, or
pushed and twisted. Such twist-lock mechanisms are known in the art
and are contemplated herein as an alternative embodiment of
retaining the modular heater within the pocket.
[0094] In another embodiment shown in FIG. 17, a modular heater
1300 may be friction or press fit into an associated pocket of a
container. Heater 1300 includes a press fit band 1302 to secure
heater 1300 to pocket in container 1310. Band 1302 is preferably
slightly wider than body 1301 of heater 1300, allowing a secure fit
of the band into pocket of container 1310 while providing clearance
between body 1301 and container 1310. The rounded contour of the
heater edge 1304 provides a lead in for insertion. Heater band 1302
may optionally include one or more air vents 1306 to provide a
venting mechanism for the heater 1300 during heating to allow any
resulting gases to escape and prevent air lock.
[0095] An additional embodiment is shown in FIGS. 18A and 18B,
where heater 1400 is engaged by slip fit with adhesion to the
container or package by use of a suitable adhesive 1404. In FIG.
18A, diameter of heater 1400 is sized to slip fit into pocket of
container 1410, and a suitable thermal adhesive 1404 (such as
Duralco 4703 high temperature epoxy which is stable to 340.degree.
C.) in the pocket of container 1410 secures heater 1400 to
container 1410. In another alternative embodiment shown in FIG.
18B, diameter of heater 1500 is sized to slip fit into pocket of
container 1510. To secure heater 1500 to container 1510, heater
1500 is bonded to an external bottom insulation layer 1502 using a
suitable thermal adhesive 1504. Insulation layer 1502/heater 1500
assembly is then bonded to bottom of container 1510 using thermal
adhesive 1504.
[0096] In additional embodiments shown in FIGS. 19A-C, heater can
be "snap fit" into container. In the embodiment shown in FIG. 19A,
diameter of heater 1600 is sized to fit into pocket of container
1610 and includes a circumferential ridge 1602 that has a diameter
wider than diameter of body 1601. Pocket of container 1610 includes
a groove 1612 around the circumference of opening for receiving
ridge 1602, such that when heater 1600 is inserted into pocket of
container 1610, ridge 1602 snaps into groove 1612 for securing
heater 1600 to container 1610. FIG. 19B shows an alternative heater
1700 which includes four or more protrusions 1702 that can snap fit
into groove 1612 of container 1610 pocket. The embodiment shown in
FIG. 19C is another alternative snap-fit embodiment. In this
embodiment, container 1810 has a ridge 1812. Heater 1800 is sized
such that it is snap-fit into opening by pushing it past the ridge
1812, whereby the ridge 1812 will hold heater 1800 in place in
opening of container 1810.
[0097] In another embodiment (not shown) heater may engage with a
container by shrink fit, such as by cooling heater to shrink it and
inserting it into a pocket of container, whereby warming of the
heater will cause it to expand for a firm fit in the pocket of
container. Alternatively, container may be heated for expansion of
the pocket and after heater is inserted, container cools and
shrinks to securely contain heater. In yet another embodiment (not
shown), heater may be mechanically attached to container by spot
welding, or by threading the heater to threads on the inside of the
opening of container.
[0098] As previously noted, the pocket may be configured in
numerous geometries and cross-sections, some of which may be
dictated or influenced by the geometry or type of container or
package. A particularly suitable pocket geometry for can ends of
canned food designs is a relatively shallow pocket incorporating a
draft angle such that a cross-section of the pocket resembles a
general trapezoidal shape. The shallow depth and the draft angle
makes the can end more easily manufactured. The draft angle also
facilitates stacking of multiple can ends, which provides
efficiency in shipping and storage of can ends. In such an
embodiment, the can ends can be nested together by virtue of the
pocket having the draft angled sidewall(s). Furthermore, as shown
in FIGS. 14, 20A and 20B, in certain embodiments, rather than a
right-angled cylinder or disc shape, the modular heater may
incorporate a housing having a similar draft angle design that
correspondingly engages the pocket having the draft angled
sidewall(s).
[0099] In another embodiment, such as that shown in FIG. 20A, in
lieu of, or in addition to a flexible housing portion, a flexible
insulating layer of material 1902 may be "overlaid" on top of a
modular heater 1904 and activation mechanism 1906 and affixed
thereto, essentially sealing the activation mechanism 1906 and
providing additional thermal safety to the user. The insulating
layer 1902 may be welded, adhered, or otherwise affixed to the
heater. In yet another embodiment, such as that shown in FIG. 20B,
a cap 1908 or other cover may be formed to cover the activation
mechanism 1906 and the heater 1904, such as a cap or cover made
from an insulative foil or other material utilized in heated food
product applications. The insulating layer 1902 or the cap could be
implemented individually or in combination and be configured to
allow the activation mechanism to be operated with them in
place.
[0100] The principles of the present invention may also be applied
for use in a "hybrid" package arrangement that utilizes both metal
and plastic components. For example, a plastic bowl or other
container may be formed with a metal bottom incorporating the
aforementioned pocket, which accommodates the modular heater. The
metal material is able to withstand the high temperatures
attributable to the heater, while the plastic portion of the
package provides insulating properties to maintain the temperature
of the contained food heated by the heater. The "hybrid" container
or package may be formed by numerous methods known in the art for
joining metal and plastic parts, such as welding, insert molding,
etc.
[0101] In another embodiment, shown in FIGS. 21A-21E, an amount of
solid-state modified fuel 2030 is integrated into a storage can
2010 for a food or liquid 2020. As shown in FIGS. 21A-21C, the
storage can 2010 is sealed at the top by a removable lid 2070. An
opener tab 2080 is integrated onto the removable lid 2070 to aid a
user in opening the can 2010. As shown in FIG. 21D, the bottom of
the storage can 2010 is formed with an indented pocket 2090 that
allows an amount of modified reaction system fuel 2030 to be
encapsulated inside the bottom of the storage can 2010. Those of
ordinary skill in the art will also understand that the pocket 2090
can be a variety of shapes, sizes and configurations including but
not limited to the cylindrical configuration shown in FIG. 21E
without departing from the novel scope of the present
invention.
[0102] Among others, an advantage of the embodiment depicted in
FIGS. 21D and 21E, wherein the fuel or fuel device is fully
integrated or "built into" the packaging, is that there are fewer
parts and material requirements for assembly. On the other hand, as
mentioned above, an advantage of the embodiment depicted in FIG.
21E is that the fuel or fuel device is a discrete component, which
may be encapsulated or have its own device structure and be
utilized in a modular arrangement. One of ordinary skill in the art
will recognize that each of the embodiments depicted and described
herein may have unique characteristics or configurations that may
translate into one or more advantages over other depicted and
described embodiments depending on a particular application.
[0103] In normal operation of a heater containing a solid state
reaction system within a heating device, the temperatures realized
by the heated device are reduced by heat loss to the material being
heated. For example, if the heating device in FIG. 10 is filled
with water, thermodynamic considerations provide that the interior
heated surface of the vessel adjacent to the heater will
necessarily be at or below 100.degree. C., the surface temperature
being one boundary condition of a continuous thermal gradient
extending back to some maximum temperature in the heat generating
zone of the solid state chemical reaction. If only air and not
water are present in the heating device, the capacity for heat
removal is lower and the temperature of the surface is no longer
similarly bounded. In this case, with the same total heat output of
the heater, much higher temperatures can be reached at the interior
of the heater, and then by conductive transfer to the extended
surfaces of the heated package or apparatus. In food and beverage
applications, typically by design the container contents should not
exceed preferred serving temperatures of about 60 to 70.degree. C.
and for user comfort and safety no point on the surface of the
package should exceed about 54.degree. C.
[0104] The modular heater and related apparatus disclosed herein
are designed for thermal balance in normal operation by utilizing
the food mass within the container or package as a heat sink. In
the event that the material that would normally absorb the heat is
not present, for example, if the food were spilled out of the
container or if the container was accidentally not filled during
the packaging process, then excessive temperatures could be reached
within the heater or the heated apparatus upon activation of the
heater. Inadvertent activation during shipping or handling of bare
heaters not installed into a package are other potential
occurrences that could lead to severe overheating. To address these
concerns, thermal shutdown of the chemical reaction is a safety
feature that can be used with the present invention.
[0105] To prevent severe overheating, a mechanism may be
incorporated into the heater to shut it down when a predetermined
threshold temperature is sensed at a point or points in the system,
such that the heater does not discharge its full energy content. In
a preferred embodiment, from a practical cost standpoint, this
auto-shutdown functionality is achieved via a simple passive
feedback mechanism. Passive thermal shutdown of the heater could
also be used to assure that inadvertent activation of a single
heater in a container of closely packed heaters being stored or
transported would not lead to thermal activation of adjacent heater
elements, a potential fire hazard.
[0106] Other less severe circumstances may arise in which some form
of passive or active control of the heater apparatus is desirable.
For instance if just a portion of the contents to be heated was
removed from the package but the degree of overheating was not
sufficient to engage the heater shutdown mechanism, it would be
beneficial to have a means of dissipating the excess energy that
could otherwise lead to overheating of the lesser remaining
contents and package surfaces.
[0107] A heater, with a given energy content heating a given mass,
will produce approximately the same overall change in temperature;
depending on the starting temperature of the contents, different
endpoint temperatures will be achieved. Thus, where the same
heating device operating at a cold location (for example, 5.degree.
C.) would only heat a portion of soup to a dissatisfying 45.degree.
C., the heating device operated at a hot location (for example,
38.degree. C.), would heat the same portion to 78.degree. C., which
is too hot for safe consumption. Here again it would be beneficial
to provide a passive means of capping the maximum temperature of
the heated substance to provide a safer and more uniform user
experience independent of the ambient temperature.
[0108] Further, because even for the same substance to be heated
there may be varied user preferences, such that one consumer may
prefer a serving temperature of 60.degree. C. and another may
prefer 70.degree. C., it would be beneficial to incorporate a means
whereby a user preferring a lower serving temperature could
selectively dissipate some of the heat energy away from the food
portion.
[0109] The current invention includes means of achieving various
types and levels of thermal control as appropriate to the various
circumstances of need described above. These may be used in
conjunction with basic package thermal safety elements, such as
thermal insulation, heater overcap, lip guard, and thermographic
indicator labels.
[0110] With respect to auto-shutdown of the heater, it is
understood that solid state reaction kinetics are modeled as a
combustion system in which a solid flame front moves through
preheat, reaction and quench zones. For reaction self-propagation
to occur, the heat generated in the reaction zone must trigger
reaction ahead of the wave front. Disruption of the heat or mass
transfer at flame front can halt the reaction propagation.
[0111] The rates of chemical reactions generally increase rapidly
with increased system temperature such that overheating once
commenced could lead to autocatalytic thermal runaway. Thus, the
moderated solid state reaction systems of the present invention
underpin passive thermal controls of the system. The rate of
reaction and hence heat generation power is a key metric for an
energetic material in consumer heating applications. Controlled
propagation enables the rate of heat generation of the system to be
matched to the rate at which the heat can be efficiently
transferred to substance being heated. A moderated reaction
velocity also means that there is time in the system for the
passive mechanism to operate. Preferred reaction systems have
reaction propagation velocities of less than 1 mm s.sup.-1, giving
controlled heating times of about one to four minutes.
[0112] There are a variety of physical or chemical responses of
various materials that occur at certain specific temperatures or
ranges that might be used to affect such a passive auto-shutdown
mechanism. These include, for example: phase changes (solid melting
or subliming, liquid vaporizing), volume changes, and
thermochemical decomposition. Passive auto-shutdown of the solid
state reaction can be accomplished by arranging for one or more of
these material response processes, triggered by exceeding a certain
threshold temperature at some point in the heater device, to
disrupt the heat and mass transfer at the flame front of the
chemical reaction such that reaction propagation conditions are not
maintained.
[0113] For example, an auto-shutdown system could be achieved
through dimensional changes or movement of a bimetallic strip
construction integrated into the heater. For example, referring to
FIG. 3, if the reaction regulator element 120 were of a bimetallic
construction it could be arranged so that internal heating above a
predetermined threshold temperature would cause a deflection that
displaced the unreacted heater mass from contact with the flame
front.
[0114] An alternative embodiment of a passive auto-shutdown
mechanism would be the use of an intumescent material coated onto
an interior surface of the heater canister or incorporated into the
bulk matrix of the chemical composition. An intumescent material is
a substance that swells markedly (up to 100 times) as a result of
heat exposure, thus increasing in volume, and decreasing in density
and thermal conductivity to form an insulating barrier.
Intumescence can be caused by rapid evaporation and expansion of
molecules (often water) trapped in crystalline structures.
Intumescent formulations with preferred onset temperatures can be
devised by intercalating into the crystalline host matrix,
materials that evaporate, sublime, or decompose to gas products in
the temperature range of interest.
[0115] Referring to FIG. 6, one use of an intumescent material for
thermal control is to coat the inner surface 280 of the heater
container 210 beneath the solid state chemical heating composition
230 with a thin layer of sodium silicate or other intumescent such
that excessive temperatures at the surface, cause rapid, uneven
expansion of the coating, forcing sections of the solid state
reaction matrix 230 into void spaces or the compressible insulator
270 thereby breaking the contiguous connection of reaction layer
230. Low thermal conductivity of the solid state chemical heating
composition 230 reduces heat transfer and combustion rate. Thus, an
intumescent material could alternatively be incorporated into the
bulk matrix of the solid state chemical heating composition 230.
For example, powdered vermiculite (unexpanded) or other intumescent
solid could be filled into the interstitial spaces of a packed bed
of granulated particles of the solid state heating composition 230.
Whereas prior to activation and at moderate operating temperatures
the granules are packed in close thermal contact, excessive
temperatures by design lead to rapid expansion of the intumescent
phase that pushes the reactive granulate particles apart and
interrupts the propagation of heat to sustain the reaction
front.
[0116] In another alternative embodiment, a phase change might be
used to cause depletion or reduced mass transfer of an essential
reactant to the solid state reaction front. For example, one
embodiment of a solid state reaction system described herein is
sustained by a finely divided powder formed of chlorate oxidizer
uniformly distributed throughout the reactive phase. The chlorate
melts at a lower temperature and is more volatile relative to other
components present. Certain rates of heating of the reaction matrix
well ahead of the reaction front can cause some portion of the
chlorate to melt and agglomerate into a coarser distribution that
impedes mass transfer, or even evaporate and dissipate through
pores in the bed away from the heated zone before the fuel is
heated to activation temperature. Alternatively, another relatively
low melting solid material could be added into the reaction mix or
the heater such that when the solid melts, the flow of fluid
material encapsulates or otherwise disrupts mass transfer of
reactants.
[0117] Flame retardants, defined as various classes of chemicals
that are incorporated into plastics and other materials to inhibit
the spread of oxygen-supported fires, can be formulated into the
heater device or the solid state reaction matrix to prevent thermal
runaway. In yet another alternative use of reactant depletion at
the flame front to cause heater shutdown, certain flame retardants
such as organohalogen or organophosphorus compounds could slow or
stop the reaction by gas phase quenching of radical reaction
intermediates of the solid state reaction, such as oxygen ions from
the thermal decomposition of chlorate. Chlorinated and brominated
materials, for example, undergo thermal degradation and release
hydrogen chloride and hydrogen bromide that react with the highly
reactive radicals in the flame, resulting in an inactive molecule
and a Cl- or Br-radical with lower energy and thus less tendency to
propagate the radical oxidation reactions of combustion.
[0118] It is generally the case that the onset temperature of the
thermally responsive materials in relation to the normal operating
temperature of various zones in the heater or heating device, as
well as their response mode, is key in determining an appropriate
point of use, in the system. For example, organohalogen flame
retardants that are activated at temperatures of 200 to 300.degree.
C. may not be well suited for inclusion in the solid state reaction
matrix where they may too easily decompose under normal operating
conditions, but are preferentially incorporated into cooler zones
of the heater such as in the insulator component 270 or on the
interior of the heater lid 220 in FIG. 6.
[0119] Another class of flame retardants comprises chemical
compounds that undergo endothermic chemical decomposition when
subjected to high temperatures. Conventional flame retardants of
this class used in polymers include: magnesium and aluminum
hydroxides, together with various hydrates and carbonates, but
endothermic decomposition is common to a broad range of common and
low-cost materials suitable for the heater device. Table 2
describes several endothermic ally decomposing solid (EDS)
compounds, including some conventional flame retardants, which
undergo decomposition at various onset temperatures. Many of these
compounds when thermally decomposed give off carbon dioxide and/or
water as gaseous byproducts. High specific enthalpies of
decomposition that reduce the effective quantity required for
endothermic cooling are characteristic of preferred materials.
TABLE-US-00002 TABLE 2 Properties of Various Endothermically
Decomposing Solid (EDS) Compounds Approx. Approx. onset of enthalpy
of gaseous decomposition decomposition decomposition Formula
(.degree. C.) (kJ g.sup.-1 products Calcium sulfate 60-130 --
H.sub.2O [CaSO.sub.4.cndot.2H.sub.2O] Sodium bicarbonate 70-150
1.53 H.sub.2O, CO.sub.2 [NaHCO.sub.3] Alumina trihydrate 180-200
1.30 H.sub.2O [Al(OH).sub.3] Magnesium hydroxide 300-320 1.45
H.sub.2O [Mg(OH).sub.2] Huntite (mineral) 450 0.99 CO.sub.2
[Mg.sub.3Ca(CO.sub.3).sub.4] Sidertite (mineral 550 -- CO.sub.2
[FeCO.sub.3] Calcium carbontate 825 1.78 CO.sub.2 [CaCO.sub.3]
[0120] An alternative embodiment of a passive auto-shutdown
mechanism is achieved by formulating certain EDS materials into the
solid state reaction matrix, such that when a threshold temperature
is reached, their enthalpy of decomposition causes energy to be
subtracted from the system, and thereby cool or quench the heat
producing solid state reaction. Further, as with intumescent
additives, rapid expansion of the reaction matrix by gaseous
products of endothermic decomposition can be an additive
contribution to destabilization of the flame front, and EDS's with
gaseous decomposition products may also be beneficially applied as
a coating of interior heater surfaces as described earlier. In
order that they should not act prematurely, the most preferred EDS
for inclusion in the reaction mixture have an onset temperature of
300.degree. C. or higher; preferred materials, shown in Table 2,
include magnesium hydroxide, siderite, and calcium carbonate.
[0121] EDS's with lower onset temperatures shown in Table 2 may be
applied in other forms of passive thermal controls external to the
heater unit and at other points in the heating device. Referring to
FIG. 10, in an embodiment of a passive thermal control not
involving auto-shutdown of the heater reaction, a coating
containing, for example, calcium sulfate, or sodium bicarbonate or
mixtures thereof is applied to the exterior wall 620 of the heated
vessel 602. If the wall temperature then exceeds 50 to 70.degree.
C., the EDS materials in the coating will begin passive endothermic
cooling. Favorably, for higher temperature excursions, the rate of
chemical decomposition is accelerated and passive endothermic
cooling accordingly enhanced. The EDS could alternatively be
applied as a coating on the interior surface of a thermally
insulating label (not shown) to be applied around heated vessel
602, or the EDS may compounded directly into the material used to
form the insulating label.
[0122] Generally, the higher temperature zones of the heating
device will be in the vicinity of the heater's exterior surfaces
and higher temperatures in these regions will provide
correspondingly greater driving force for cooling by EDS. In
addition to calcium sulfate and sodium bicarbonate, alumina
trihydrate or other EDS compounds with slightly higher onset
temperatures would also be suitable and could be incorporated for
use in the vicinity of the heater. Positioning a mass of EDS in
close proximity to, or in contact with, the surface of the heater
can be used to effect an embodiment of a thermal control for the
heating device that can be either passive or active. For example,
referring to FIG. 20A, an appropriate point of use for the EDS mass
or component (not shown) would be in a recess between the heater
1904 and the thermal insulator 1902, or alternatively the EDS may
even be directly incorporated into the insulator 1902. In an
embodiment of passive thermal control, the EDS mass or component
would be positioned in fixed contact with the heater surface.
Alternatively providing a means for the user to vary the extent of
contact of the EDS mass with the heater or heated surfaces, and
thereby increase or decrease the endothermic cooling effect could
be used to provide a selective degree of active control to a
user.
[0123] It is noted that while the descriptions herein may make use
of the terms package, container, device, etc. to describe numerous
forms of a vessel for holding a substance to be heated in
accordance with the principles of the invention, including
reusabable, recyclable, and disposable vessels, it should be
understood that each of these terms is intended to cover all such
embodiments in a non-limiting manner. Again, consistent with other
embodiments disclosed herein, the heater may be fully integrated
with the container or package.
[0124] Again, it is noted that applications of the invention are
not limited to the SHFP applications described above. A heating
component or modular heater in accordance with the present
invention, such as the heater described above, could be
incorporated into a wide array of applications where heating would
be desirable.
[0125] While one or more specific embodiments have been illustrated
and described in connection with the present invention, it is
understood that the present invention should not be limited to any
single embodiment, but rather construed in breadth and scope in
accordance with recitation of the appended claims.
* * * * *