System, method and device for controllably releasing a product

A device, a system and a method are provided for controllably releasing a product (26) into a container (10) in which the product (26) is mixed with another product contained within an interior (14) of the container 10. The device (12) releases the product (26) due to variations in temperature or pressure that the system experiences during an autoclaving or sterilization procedure, for example. Materials and shapes of the members (20, 20a, 20b, 22) of the device (12) are selected such that the members (20, 20a, 20b, 22) react or otherwise move within the device in a predetermined manner in response to changes in temperature or pressure. As a result, products (26) within the device (12) may be maintained separately from products within the interior (14) of the container (10) in which the device (12) is held. Prior to administration of a solution within the container (10), the product (26) within the device (12) may be mixed with the solution or other product in the container (10) in a controllable fashion.

BACKGROUND OF THE INVENTION 
The present invention generally relates to a valve used in a system for 
release of a product into the system following occurrence of an event. 
More specifically, the present invention relates to a valve, a system and 
a method for controllable release of a product which requires separation 
from a remainder of the products contained in a system. 
A major function of a kidney is to maintain an acid-based homeostasis in 
the body. A patient requiring renal dialysis relies on a buffer provided 
in a dialysate for this function. A natural buffer which is present in the 
body is a bicarbonate buffer. Therefore, using a bicarbonate buffer is a 
natural choice for combination with a dialysate. However, bicarbonate when 
mixed with dextrose contained in dialysate causes the dextrose to degrade 
at the high temperatures that are used during autoclaving. Therefore, 
lactate has often been used as a substitute for bicarbonate. 
Solution biocompatability is, of course, a major concern in dialysis. 
Therefore, combining dialysate with a bicarbonate buffer has been 
seriously pursued. Accordingly, many endeavors have been undertaken to 
develop a bicarbonate solution for use in dialysis. 
One such known method is to incorporate a dual-chamber bag. In this system 
and method, two solutions are contained in two separate chambers of a bag 
that are integrally formed. Between the chambers of the bag is a 
frangible. When the frangible is broken, the two solutions are admixed. 
However, such a system is difficult to manufacture, and the material costs 
required to produce the dual-chamber bag are high. 
Of course, a number of other applications require separation of components 
prior to use due to compatability issues. For example, a number of 
intravenous solutions require separation, such as dextrose and heparin, 
chemotherapy drugs and antibiotic drugs. Other peritoneal dialysis 
solutions also require separation besides dextrose and a buffer, such as 
polyglucose and a buffer; dextrose or polyglucose and a peptide or amino 
acids; and Dianeal.RTM. and heparin. 
A need, therefore, exists for an improved device, system and method for 
controllably releasing a component, such as bicarbonate, into a solution 
or second component for mixing of the component with the solution. 
SUMMARY OF THE INVENTION 
The present invention relates to a device, a system and a method for 
controllably releasing a component. The device of the present invention 
sealingly holds the component until a predetermined event, such as a 
change, in an external condition, occurs causing release of the component 
into another container having a solution therein. As a result, the 
component is mixed with the solution. 
To this end, in an embodiment, the present invention provides a system for 
controlling release of a component. The system has a container having 
walls defining an interior capable of holding a product therein wherein 
the product requires mixture with the component. A device exposed to the 
interior of the container has walls defining an interior. A plug member 
encloses the interior wherein the interior holds the component for mixing 
with the product in the container. 
In an embodiment, the plug member is constructed from material designed to 
alter its shape due to changes in temperature. 
In an embodiment, the plug member is designed in a shape to alter position 
of the plug member in the device due to variations in pressure. 
In an embodiment, a cap member encloses an end of the device remote from 
the plug member. A second plug member may be located intermediate the cap 
member and the plug member in the interior of the device. The second plug 
member may be designed in a shape that alters its position in the device 
due to variations in pressure. 
In an embodiment, the component is a buffer used in a dialysis procedure. 
In an embodiment, the product is a solution including dextrose. 
In another embodiment of the present invention, a method is provided for 
controlling release of an agent. The method comprises the steps of: 
providing a container having an interior capable of holding a product 
therein; filling a device with the agent; sealing the agent in the device; 
providing the device in the interior of the container; altering a 
condition that is applied to the container; and releasing the agent from 
the device due to the altered condition. 
In an embodiment, a plug member is provided sized to seal and enclose one 
end of the device wherein the plug member is responsive to changes in 
temperature. 
In an embodiment, a plug member is provided sized to seal and enclose one 
end of the device wherein the plug member is responsive to changes in 
pressure. 
In an embodiment, the agent is a buffer requiring mixture with the product 
for use in a dialysis procedure. 
In an embodiment, the product is a solution having dextrose therein. 
In an embodiment, the temperature is increased to subject the container to 
sterilization. 
In another embodiment of the present invention, a device is provided having 
an agent therein for controllable release of the agent into a system. The 
device has a wall defining an interior that is accessible via an open end 
wherein the interior holds the agent. Further, a cap member is sized to 
seal and enclose the open end wherein the agent is enclosed and sealed in 
the interior and further wherein the cap member is responsive to a change 
in an external condition causing alteration of the cap member to release 
the agent. 
In an embodiment, a plug member is located remotely from the cap member 
wherein the plug member is responsive to the change in the external 
condition. The cap member and the plug member are shaped to respond to 
changes in pressure. The cap member and the plug member may further be 
distinctly shaped from each other. 
In an embodiment, the cap member has a core and a shell each made of 
distinct materials wherein each material reacts differently in changing 
temperature conditions. 
In an embodiment, the agent is a buffer requiring mixture with a solution 
prior to administration to a patient undergoing a dialysis procedure. 
In an embodiment, the external condition is varying pressure. 
In an embodiment, the external condition is varying temperature. 
In an embodiment, the wall has an integrally formed surface directed to the 
interior. 
It is, therefore, an advantage of the present invention to provide a 
device, a system and a method for separating at least two components. 
Another advantage of the present invention is to provide a device, a system 
and a method for simplifying separation of at least two components. 
Yet another advantage of the present invention is to provide a device, a 
system and a method for controllably releasing a component into another 
component. 
A still further advantage of the present invention is to provide a cost 
effective device, system and method for separating at least two components 
and controllably releasing at least one component into another component. 
Moreover, an advantage of the present invention is to provide a device, a 
system and a method that automatically releases one component into another 
component during normal use of the system. 
And, another advantage of the present invention is to provide a device, a 
system and a method that reliably maintains separation between at least 
two components and also reliably controls release of one component into at 
least one other component. 
Yet another advantage of the present invention is to provide a device, a 
system and a method for controllably releasing a component into another 
component that is simple for a customer to use. 
A still further advantage of the present invention is to provide a device, 
a system and a method for controllably releasing a component that is 
inexpensive to manufacture and to implement.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
The present invention generally relates to a controllable release valve or 
device, a system and a method for controllably releasing a product into 
another product. The system is particularly applicable for use in 
controllably releasing a component into a noncompatible component prior to 
use of the combined components. Such a system is particularly useful in a 
dialysis procedure wherein a device is provided containing sodium 
bicarbonate which must be maintained separately from a solution containing 
dextrose as sodium bicarbonate causes degradation of dextrose at high 
temperatures. 
Referring now to the drawings wherein like numerals refer to like parts, 
FIG. 1 generally illustrates a container 10 having a device 12 of the 
present invention therein. The container 10 has an interior 14 formed by 
exterior walls 16. Typically, the walls 16 of the container are a 
thermoplastic material, but any material for the walls 16 are within the 
scope of the present invention. The interior 14 of the container 10 is 
capable of holding a solution or other component therein. 
The device 12, as illustrated, is loosely suspended within the interior 14 
of the container 10. However, it should be appreciated that the device 12 
may be attached by a hanging mechanism (not shown) such that the device 12 
is removably held in the interior 14 of the container 10. The container 
10, as illustrated, includes two ports 18 providing fluid communication 
with the interior 14 of the container 10. Of course, a single port 18 or 
additional ports may be provided as required for the particular embodiment 
in which the invention is used. 
The device 12, as illustrated in FIG. 1, is a hydrostatic valve designed 
with two plug members 20a, 20b and a cap member 22. The plug members 20a, 
20b, as illustrated, are designed having distinct shapes such that each 
operates slightly different under varying temperature and/or pressure 
conditions. Of course, it should be appreciated that a single plug 20' may 
also be implemented as will be described with reference to FIG. 2 or, 
alternatively, additional plugs may also be implemented. The plug members 
20a, 20b may also be identically shaped for a particular application in 
which the same may be appropriate. In addition, the cap member 22 may be 
connected to the plug member 20a such that when the cap member 22 is 
forced from the device 12, as illustrated in FIG. 4, the cap member 22 
does not randomly release into the interior 14 of the container 10. To 
this end, a connecting member 21 may be provided that maintains the cap 
member 22 in spaced relation to the plug member 20a. 
The device 12 has an interior section 24 in which a product 26, such as, 
for example, a buffer, may be stored prior to admixture with a component 
in the interior 14 of the container 10. During manufacture, the device 12 
containing the product 26 may be inserted into the container 10 during a 
container forming process. The container 10 is then filled with a solution 
in the interior 14 of the container 10 containing all of the necessary 
ingredients required for a procedure, such as peritoneal dialysis. As 
previously mentioned, the device 12 may be floating or fixed within the 
interior 14 of the container 10. 
The product 26, either in solid or in liquid form, is, therefore, sealed 
inside the device 12 and isolated from the bulk of the solution within the 
interior 14 of the container 10. The container 10 may then be separately 
pouched in an overpouch as required for the particular application. The 
container 10, with or without the overpouch, may then be autoclaved or 
heat sterilized as required. 
During a sterilization procedure, the dynamics of the device 12 takes 
place. To prevent the container from exploding, an overpressure is 
required within an autoclave chamber in a standard autoclave cycle during 
which time the temperature within the chamber is raised. The overpressure 
compresses the device 12 thereby pushing the plug members 20a, 20b toward 
the cap member 22. Under compression, the seal is maintained between a 
product 26 and the solution in the interior 14 of the container 10. 
At the completion of the cycle, pressure drops after the chamber is cooled 
off. When chamber pressure decreases, pressure inside the device 12 
becomes greater than an exterior pressure. Then, internal pressure within 
the interior section 24 of the device 12 becomes so strong so as to push 
off the cap member 22 and release the product 26 into the interior 14 of 
the container 10 to mix with the solution contained therein. The admixing 
thereby occurs automatically at a cooler temperature, and the interaction 
between the product 26 and the solution is prevented during heat 
sterilization or the autoclave cycle in which it is not possible to mix 
the solution in the interior 14 of the container 10 with the product 26 in 
the interior section 24 of the device 12. 
The above-described process is clearly illustrated with reference to the 
graph of FIG. 13. As shown from the graph, the plug member and cap member 
react due to changes in pressure conditions in the system during the 
autoclave cycle. In addition, the plug member 20b is designed such that 
the friction with the walls of the device exceeds the friction from the 
cap member 22 containing the product 26 and any additional plug members 
between the cap member and the most extreme plug member 20a. In addition, 
both the plug member and the cap member may be designed as one way plugs 
such that movement of the plug members and the cap member only occurs in a 
single direction. 
Referring again to the graph of FIG. 13, two separate activations are 
required in order for the cap member 22 to be removed from the device 12. 
Namely, during the autoclave cycle, when external pressure is large, the 
plug member 20 is pushed inward into the device 12. During cooling, the 
internal pressure becomes greater forcing the cap member 22 to pop out 
thereby releasing the component 26 contained in the device 22. The 
component 26 is thereby released into the interior 14 of the container 10. 
As previously mentioned, the plug member 20 and the cap member 22 may be 
connected such that the cap member 22 does not stray from the device 12 in 
the interior 14 of the container 10. 
In a preferred embodiment, the plug and cap members 20a, 20b and 22, 20b 
are made from silicon elastomer. Using the additional plug member 20a at a 
middle point of the device 12, both of the plug members 20a, 20b move 
toward the cap member 22 the same way as one plug member moves within the 
device 12. With the additional plug member 20a, a better seal may be 
achieved and a physical push to cap member 22 can be generated. 
Referring now to FIG. 2, a single plug member 20' is shown within a device 
12' with a cap member 22' enclosing an interior section 24' in which a 
product 26' is sealed therein. The device operates in a similar manner as 
the two plug member design except that an extra plug member is not 
provided to maintain the integrity of the seal. In a preferred embodiment, 
the plug member may be constructed from a polyvinylchloride (PVC) 
material. Of course, other materials may be implemented by those skilled 
in the art. 
FIGS. 3 and 4 illustrate the device 12 as described with reference to FIG. 
1 incorporating the dual plug members 20a, 20b within the interior 24 of 
the device 12. Again, a single cap 22 encloses the interior of the 
container and is constructed such that a seal is maintained between an end 
25 of the device 12 maintaining the product 26 within the interior section 
24 of the device 12. During cooling of the device, pressure inside the 
device 12 becomes stronger thereby forcing removal of the cap member 22 
from the end 25 of the device 12 and thereby allowing the product 26 to 
escape from the device 12. As previously stated, the plug member 20 also 
advances within the interior 24 of the device 12 maintaining the integrity 
of the seal from an opposite end of the cap member 22. 
The hydrostatic valve design shown and described in FIGS. 2-4 and further 
shown and described with reference to FIGS. 5-10 is designed for processes 
which undergo pressure difference cycles, such as, for example, autoclave 
sterilization cycles under overpressure conditions. The activation member 
for opening the valve or plug member 20 or the cap member 22 is the volume 
expansion of air by pressure differences. The device 12 as previously 
described including the cap member 22 is designed to be incapable of 
moving into the device 12 under high external pressure, but opens under 
high internal pressure. The moving part or plug member 20, 20a and/or 20b 
is designed such that the plug member only moves within the device 12 
under high external pressure but does not move out as easily as the cap 
member during high internal pressure. In addition, as previously 
described, the plug member 20 and the cap member 22 are designed such that 
the friction in the most distant plug member from the cap member exceeds 
the friction of the other plug members, if any, and the cap member 22. 
Further, friction forces between the walls of the device 12 and the plug 
member 20, 20a and/or 20b and the cap member 22 are critical since the 
friction forces dominate both compression and expansion processes, i.e. 
less friction force for the cap member 22 (at least less than the 
expansion force on the cap member 22) and a higher friction force for the 
plug member 20, 20a and/or 20b during the opening process. A higher 
friction force is required for the cap member 22 and a lesser friction 
force is required for the plug member 20, 20a and/or 20b during a 
compression process. The friction forces can be controlled by a proper 
choice of material and the specific designs of the plug member 20, 20a 
and/or 20b and the cap member 22. The interfacial friction forces also 
contribute to the degree of sealing between the walls of the device 12 and 
the plug member 20, 20a and/or 20b and the cap member 22. 
As illustrated in FIGS. 5-9, different design shapes of the plug members 20 
are illustrated, either for the single plug design or the double plug 
design. The shape of the plug member 20 is designed for easy opening of 
the hydrostatic valves. For some products 26 contained in the device 12, 
for example, certain drugs, their dissolution rate in water is controlled 
by device shapes and wetability which dictate the contact between water 
and drugs. The improvement in surface hydrophilicity of the device 12 
should be helpful to dissolve the contained drug into water by increasing 
the contact area between water and the drugs. Some surface modification 
treatments have been employed for this purpose, such as plasma treatment 
of the surfaces of the device 12; inorganic acid treatment of internal 
surfaces of the device 12; blending a water-soluble polymer into shell 
materials to improve surface wetability; and coextruding a hydrophilic 
layer on the internal surface of the devices. These surface treatments 
improve the surface hydrophilicity. 
As illustrated in FIGS. 5-9, the different designs of the plug member 20 
allow movement of the plug member 20 within the device 12 in the direction 
of the arrow, but not in the direction of the oppositely directed arrow 
having an "X" therethrough. As further illustrated in FIG. 9, an interior 
wall of the device 12 may be formed with a ramp 13. The ramp 13 may be 
integrally formed and is designed as a stopping member, i.e. to stop 
back-off or return of the plug member 20 in the device 12 during external 
pressure releasing. Of course, any of the other embodiments of the device 
12 may also implement the ramp 13. The ramp 13, however, may simply be 
replaced by an indent or deformation formed in the wall of the device 12. 
FIG. 10 illustrates the effects of both pressure and temperature within the 
device 12 to the cap member 22 and the plug member 20. The process of 
movement of the plug member 20 and subsequent movement of the cap member 
22 from changing pressure conditions has been previously described with 
reference to FIGS. 1-4. In FIG. 10, the construction of the wall of the 
device 12 is also designed to collapse during changes in pressure and 
temperature conditions. As a result, with the plug member 20 designed as 
shown in FIG. 10, the wall of the device 12 collapses to affix the plug 
member 20 in the device 12 thereby limiting any further movement. 
Referring now to FIGS. 11 and 12, alternate embodiments to the embodiments 
illustrated in FIGS. 1-10 are shown. In FIGS. 11 and 12, a thermal valve 
100 is illustrated. The thermal valve 100 operates under the principles 
governed by thermal expansion and contraction between polymer materials 
during heating and cooling cycles and the different swelling capabilities 
of polymers in an aqueous environment. The differences in thermal 
expansion or water swelling between two polymers can generate a 
significant gap during the heating and cooling cycles from a proper choice 
of materials for the members of the thermal valve device 100. Proper 
materials allow a separation or opening of the thermal valve 100 under a 
small driving force, such as gravity, for example. 
FIGS. 11 and 12 illustrate an example of a thermal valve 100 with the 
thermal expansion/contraction of different kinds of polymer materials. 
With the change in polymer structure and morphology, a variety of 
transition behaviors can be used to generate a volume difference during 
heating and cooling cycles thereby creating a gap between the various 
materials. As illustrated, two distinct materials form a core 102 and a 
shell 104. 
In a first example, as illustrated in FIG. 11, shell material transverse 
deformation results from selection of a shell material of a polymer having 
a low thermal expansion polymer and a lower mechanical strength against 
deformation at ultimate use temperature (UUT) as well as a lower water 
swelling capability. A core polymer is selected having a high thermal 
expansion polymer, a high elastic modulus, thermoset, high water swelling 
capability, melting temperature (T.sub.m) or glass transmit temperature 
(T.sub.g) less than UUT and a higher mechanical strength than the polymer 
of the shell 104 at UUT. 
In another example illustrated in FIG. 12, a core material is subjected to 
longitudinal deformation. A polymer is selected for the shell 104 of a low 
thermal expansion polymer: that is, T.sub.g or T.sub.m is greater than the 
UUT and has enough mechanical strength at UUT. The polymer of the core 
material is a high thermal expansion polymer with T.sub.g or T.sub.m less 
than UUT. As a result, a gap is formed between the edge of the core member 
and an internal radius of the shell member 104 as shown in FIG. 12. 
As a result of the selection of the proper polymers, a gap is created 
between the shell 104 and the core 102. The kind and size of the gap can 
be theoretically predicted by a calculation based on thermal expansion and 
contraction behavior of specific polymers. 
EXAMPLE 1 
The shell material (polymer S) is assumed to be polypropylene (PP, T.sub.m 
&gt;150.degree. C.), and the core material (polymer C) is a linear low 
density polyethylene (LLDPE, T.sub.m &lt;120.degree. C.). The UUT is assumed 
to be 120.degree. C. according to normal autoclave temperature. Therefore, 
the (T.sub.m).sub.LLDPE &lt;UUT&lt;T.sub.m PP condition can be satisfied. The 
thermal expansion coefficients for PP and LLDPE within the temperature 
range of 25.degree.-120.degree. C. are similar (about 10.sup.-4) since 
this temperature range is far higher than their T.sub.g 'S. It can be 
reasonably assumed that the volume difference due to thermal expansion may 
be ignored in this circumstance. That is, the volume difference necessary 
to generate a thermal gap is solely dependent from crystallization/melting 
transition of LLDPE. With heating from 25.degree. C. to 120.degree. C., 
LLDPE undergoes a melting transition but PP does not. Hence, LLDPE has a 
dramatic volume expansion by the change of crystalline phase to amorphous 
phase. With cooling from 120.degree. C. to 25.degree. C., LLDPE undergoes 
a crystallization transition but PP does not. Thus, LLDPE has a dramatic 
volume contraction by changing from an amorphous phase to a crystalline 
phase. And, a gap is created by the volume change of LLDPE during 
heating/cooling cycles due to a relatively constant volume of PP during 
this heating/cooling cycle, i.e. a longitudinal deformation of LLDPE 
producing a thermal gap. The following calculation gives a quantitative 
estimation of the size of the gap. A schematic presentation of a thermal 
valve device is used in the calculation as illustrated in FIG. 15, where L 
is the longitudinal thickness of the device, which is the same for the 
shell and the core, 3.0 mm is used in this case; r is the diameter of the 
valve, 73 mm is used in this case; x is the gap distance. The densities of 
crystalline PE and amorphous PE are 1.0 and 0.855, respectively. The 
crystallinity (X.sub.c) of LLDPE is reasonably cited as 40 wt. %. The core 
materials (LLDPE) weight is assumed to be 0.11 gram. Therefore, the 
amorphous volume (Va) and crystalline volume (Vc) of PE can be calculated 
as: 
EQU Va=0.11/0.855=0.1287 cm.sup.3, 
and 
EQU Vc=0.11/1.0=0.1100 cm.sup.3. 
The volume difference between Va and Vc is then: 
EQU V=Va-Vc=0.0187 cm.sup.3 
For X.sub.c =40 wt. %, the volume of semicrystalline LLDPE can be 
calculated as: 
EQU Vc+a=X.sub.c Vc+(1-X.sub.c) Va=0.1212 cm.sup.3. 
Thus, the volume difference between Va+c and Va, which is the total volume 
to be used to create a thermal gap, is calculated as: 
EQU Vr=Va-Va+c+0.007507 cm.sup.3 =7.753 mm.sup.3. 
The following equation is then obtained: 
EQU Vr=r.sup.2 L-(r-X).sup.2 L 
where Vr=7.753 mm.sup.3, t=7.40 mm, L=4.00 mm. Then, the gap distance x 
which is generated by heating/cooling cycle can be calculated as 0.055 mm 
under assumed conditions. This gap is believed to be large enough for the 
thermal valve opening gravity force. 
The material selected for use with the thermal valve may be classified into 
two different kinds: 
(1) Material matches which can generate core material longitudinal 
deformation; the polymer of the shell material may be any of the 
following: 
Polymer S: PP, PS SAN, PMMA, Nylon polyimids, PC, polysulfones, PCCE, 
PVF.sub.2, Taflon, High T polyesters, their blends, and those polymers 
whose T.sub.g or T.sub.m is higher than UUT (for autoclave cycle, UUT is 
120.degree. C.). 
The polymer of the core material may be any of the following: 
Polymer C: crosslinked PE, low T.sub.m polyesters, polyethers, isonomers, 
rubbers, their blends, and those polymers whose T.sub.g or T.sub.m is 
lower than UUT (or autoclave cycle UUT is 120.degree. C.). 
The material matches create shell material transfer deformation wherein 
polymers of the shell material may be any of the following: 
Polymer S: PE/PP blends, crosslinked PE, PS, their blends, and those 
polymers which have low thermal expansion, high permanent set, low 
mechanical strength against deformation at UUT, low water swelling 
capability. 
And the polymer of the core material may be any of the following: 
Polymer C: crosslinked rubbers, PU, other synthetic elastomers, hydrogels, 
EVOH, their blends, and those polymers which have high thermal expansion, 
high elastic modulus, high water swelling capability at UUT. 
Referring to FIGS. 14(A)-(I), various embodiments of hydrostatic and 
thermal valves are illustrated. FIGS. 14(A), 14(C), 14(D), 14(F) and 14(I) 
illustrate various core (C) and shell (S) embodiments in which the thermal 
valve theory can be implemented. The proper materials for the core and 
shell are selected such that the core and the shell react to changing 
temperatures causing a separation and/or deformation between the shell and 
the core. As a result, a component that is sealed within the device using 
the thermal valve with the shell and core can be released into another 
area. 
In FIGS. 14(B), 14(G) and 14(H), various alternate embodiments of a device 
100', 100" and 100'", respectively, implementing the hydrostatic valve 
principle are shown. FIG. 14(E) illustrates an alternated design of a plug 
member 120'. FIG. 14(G) illustrates an embodiment in which the device 100" 
of the present invention replaces one port 102" of a plurality of ports 
that provide fluid communication with an interior 105 of a container 110. 
Although the present invention has been described with respect to mixing of 
drug solutions, the present invention may also be implemented for 
application in the food and beverage industry. Often, instant food and 
beverages require a heating process before eating or drinking, and some 
food ingredients or beverage additives cannot be heated together to avoid 
spoiling the taste. Instead of inconvenient and time-consuming separate 
mixing, separate products may be placed in the device 12 of the present 
invention with a thermal or hydrostatic valve within the device and within 
the container and, after heating, the customer will receive a ready-to-eat 
food or drink. 
It should be understood that various changes and modifications to the 
presently preferred embodiments described herein will be apparent to those 
skilled in the art. Such changes and modifications may be made without 
departing from the spirit and scope of the present invention and without 
diminishing its attendant advantages. It is, therefore, intended that such 
changes and modifications be covered by the appended claims.