Abstract:
A tray for selectably heating or cooling the contents of the tray comprises a container body having a material chamber for containing said contents. The tray is specifically configured to heat of cool solid, semi-solid or viscous materials. The container body is generally flat wherein the width of the container body is greater than its height. The container body has a first compartment for housing a thermic module and a second compartment for containing the contents to be heated or cooled. Within the thermic module, an internal exothermic (or, alternatively, endothermic) chemical reaction is initiated to heat (or cool) the contents when a user actuates the thermic module. The thermic module comprises two reactant chambers separated by a breakable barrier, an actuator, and a piercing member movable between a retracted position and an extended position in response to a force placed on a portion of the actuator. A distal end of the piercing member breaks said breakable barrier when the piercing member is forced into the extended position to allow mixing of the reactants in the two reactant chambers.

Description:
[0001]     This is a continuation-in-part of U.S. patent application Ser. No. 10/800,802, filed Mar. 15, 2004. The contents of the aforementioned patent application is hereby incorporated herein by reference in its entirety. Priority to the aforementioned application is hereby expressly claimed in accordance with 35 U.S.C. § 120 and any other applicable statutes or laws. 
     
    
     BACKGROUND OF THE INVENTION  
     Field of the Invention  
       [0002]     The present invention relates generally to containers that include an internal module that adds heat to or removes heat from a material, such as a food, beverage, medicine, or the like, in the surrounding container.  
         [0003]     Containers may have integral modules for warming materials in the container, such as sake, coffee, or soup. Examples of such self-heating containers are disclosed in U.S. Pat. Nos. 5,461,867; 5,626,022; and 6,351,953 issued to Scudder et al. All patents, patent applications and other publications referenced in this application are hereby incorporated by reference herein in their entirety. Such containers typically include an outer can or body, in which the food or beverage is sealed, and an inner can or thermic module that contains two chemical reactants that are stable when separated from one another but, when they mix in response to actuation of the thermic module by a user, produce an exothermic reaction or, alternatively, an endothermic reaction and thereby heat or cool the contents of the container.  
         [0004]     As part of the manufacturing process of such containers which are used for holding food and beverages, the containers must go through a sterilization process called “retort.” In general the retort process consists of subjecting the container and food contents to high temperatures and pressures. In a typical retort process, the container and contents are placed in a chamber for several minutes at 252 degrees Fahrenheit and two bars of pressure. Accordingly, the containers must be designed to withstand the retort process and still function properly.  
         [0005]     The heating or cooling module (thermic module) is typically attached at one end of the cylindrical container body, and the elongated cylindrical reaction chamber portion of the module extends into the container body. This elongated portion functions as both a chamber in which to contain the reaction and a heat-exchanger for transferring heat between it and the surrounding contents of the container body. The thermic module has two chambers, each of which contains one of the chemical reactants, separated by a breakable barrier such as metal foil or a thin plastic film. Typically, one of the reactants is a liquid, and the other is in a solid powdered or granular form. Calcium oxide (commonly known as limestone) and water are examples of two reactants known to produce an exothermic reaction to heat the contents in such containers. Other combinations of reactants are known to produce endothermic reactions to cool the container contents. A cap containing the liquid reactant is disposed in the end of the thermic module attached to the container body. At one end of the cap is an actuator button that a user may press to initiate the heating or cooling. The barrier seals the other end of the cap. The cap has a pushrod or similar prong-like member that extends from the actuator button nearly to the barrier. Depressing the actuator button forces the prong into the barrier, puncturing it and thereby allowing the liquid reactant to flow into the solid reactant in the reaction chamber. The heat produced by the resulting exothermic reaction or absorbed by the resulting endothermic reaction is transferred between the reaction chamber of the thermic module and the contents of the container body by conduction. Exothermic reactions also typically generate a gas and/or steam, which is allowed to escape through vents in the end of the container. The user inverts the container and, when the contents have reached the desired temperature, consumes the contents. The second end of the container body has a seal or closure, such as a conventional beverage can pull-tab, that may be opened and through which the user may consume the heated or cooled contents.  
         [0006]     These elongated containers having elongated, cylindrical thermic modules and container bodies are best suited for heating or cooling liquid materials such as drinks, soups or other less viscous food products. The elongated containers are not as useful for solid, semi-solid or viscous food products, such as stew, chili, chicken, beef or the like. This is true for several reasons. First of all, the elongated container body is similar to a typical drinking container like a drinking glass or cup where the contents are consumed by drinking directly out of the container. The relatively small top surface of the elongated container body limits the size of the opening that can be provided for consuming out the contents of the container. This is fine for drinking or pouring directly out of the container, but when eating with a utensil such as a fork, spoon and/or knife, it is undesirable.  
         [0007]     In addition, the heating or cooling of a liquid or low viscosity food product creates natural convection to distribute the heat from the heat source (cooling from the cold source, as the case may be) throughout the contents of the container. Moreover, minor movements or shaking of the container mixes the liquid further distributing the heat. With solid or more viscous contents, the heat from the heat source is non-uniformly applied to the food contents nearest the interface of the thermic module and the container body and heat is distributed mainly by conduction.  
         [0008]     Accordingly, the present invention is directed to improvements in self-heating and self-cooling containers for solid, semi-solid or viscous food products which overcome these problems and deficiencies of previous containers.  
       SUMMARY OF THE INVENTION  
       [0009]     The self-heating or self-cooling tray of the present invention is particularly configured for heating or cooling solid, semi-solid or less viscous materials. The following description of the invention will be directed to the self-heating version for heating food products with the understanding that the invention also encompasses self-cooling simply by replacing the exothermic reaction with an endothermic reaction and the food products may be replaced by any contents to be heated or cooled.  
         [0010]     The self-heating tray comprises a container body which is in the shape of a tray or a bowl. The tray or bowl can by round, rectangular, oval or any other suitable bowl shape. The container body is relatively flat in dimension as opposed to being tall or elongated. In other words, the container body has a height and a width, wherein the width of the container body is greater than the height of the container body. For example, the width is preferably twice the height, or the width is between two times and four times the height, or the width is at least twice the height.  
         [0011]     The container body has two compartments. A first compartment comprises the bottom portion of the container body and houses a thermic module disposed in the first compartment. The upper portion of the container body forms a second compartment. The second compartment holds the food product(s) to be heated. The second compartment may directly contain the food products, or the food products may be contained in a separate food container that is then placed into the second compartment. The separate food container may be held in the second compartment by a snap-fit, by an adhesive or any other suitable means.  
         [0012]     The thermic module has two reactant chambers. The first reactant chamber contains a first reactant that is physically separated from a second reactant contained in the second reactant chamber. When a user actuates the thermic module, the reactants mix and produce a reaction that, depending upon the reactants, either produces heat, i.e., an exothermic reaction, and thereby heats the container contents, or absorbs heat, i.e., an endothermic reaction, and thereby cools the container contents.  
         [0013]     The foregoing, together with other features and advantages of the present invention, will become more apparent when referring to the following specification, claims, and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     For a more complete understanding of the present invention, reference is now made to the following detailed description of the embodiments illustrated in the accompanying drawings, wherein:  
         [0015]      FIG. 1  is an exploded perspective top view of a self-heating tray assembly of the present invention;  
         [0016]      FIG. 2  is an exploded perspective bottom view of the self-heating tray;  
         [0017]      FIG. 3  is a side view of the self-heating tray;  
         [0018]      FIG. 4  is a cross-sectional view taken along line  4 - 4  of  FIG. 3 ;  
         [0019]      FIG. 5  is a top view of the self-heating tray;  
         [0020]      FIG. 6  is a side view of the container body of the self-heating tray of  FIG. 1 ;  
         [0021]      FIG. 7  is a cross-sectional view taken along line  7 - 7  of  FIG. 6 ;  
         [0022]      FIG. 8  is a side view of the thermic module of the self-heating tray of  FIG. 1 ;  
         [0023]      FIG. 9  is a cross-sectional view taken along line  9 - 9  of  FIG. 8 ;  
         [0024]      FIG. 10  is a side view of the food container of the self-heating tray of  FIG. 1 ;  
         [0025]      FIG. 11  is a cross-sectional view taken along line  11 - 11  of  FIG. 10 ;  
         [0026]      FIG. 12  is a graph of transient temperature curves for calcium oxide particles of various sieve sizes.  
         [0027]      FIG. 13  is a graph of transient temperature curves for calcium oxide particles of various sieve sizes.  
         [0028]      FIG. 14  is a graph of transient temperature curves for calcium oxide particles of various sieve sizes.  
         [0029]      FIG. 15  is a graph of transient temperature curves for calcium oxide particles of various sieve sizes.  
         [0030]      FIG. 16  is a graph of reaction/temperature curves for various ratios of water to calcium oxide.  
         [0031]      FIG. 17  is a graph of reaction/temperature curves for various ratios of water to calcium oxide.  
         [0032]      FIG. 18  is a table of mineral components in water that should not be exceeded.  
         [0033]      FIG. 19   a - 19   b  is a table of additives which may be added to the calcium oxide reactant.  
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0034]     Turning to  FIGS. 1-5 , a self-heating (or self-cooling) tray assembly  10  includes a container body  12 , a thermic module  14 , and a food container  16 . The container body  12  is shown separately from the assembly  10  in  FIGS. 6 and 7 . The container body  12  has a first compartment  18  comprising the bottom portion of the container body  12 . The upper portion of the container body  12  forms a second compartment  20 .  
         [0035]     The first compartment  18  has a relatively flat bottom surface  24  upon which the tray  10  can stably rest on a flat surface. The outer surface of the bottom surface may have a plurality of feet  28  for supporting the tray  10 . The side walls  26  of the first compartment  18  extend upwardly from the bottom surface  24 . The side walls  26  may extend upwardly and radially outward in a stepped configuration as best shown in  FIGS. 1-2  and  4 . The first compartment  18  houses the thermic module  14  which is disposed in the first compartment  18 . The bottom surface  24  has a hole  22  through which an actuator button  38  of the thermic module  14  is accessible.  
         [0036]     The second compartment  20  holds the food container  16  to be heated. The food container  16  may be held in the second compartment  20  by a snap-fit, by an adhesive or any other suitable means. The second compartment  20  may be formed in several different ways: (i) separately from the first compartment  18 ; (ii) integral to the first compartment  18 ; (iii) as part of the thermic module; (iv) or as part of the first compartment  18  and part of the thermic module  14 .  FIGS. 1-5  show the second compartment  20  being formed by the upper extension of the first compartment  20  and the upper part of the thermic module  14 .  
         [0037]     Alternative to holding the food container  16 , the second compartment  20  may directly contain the food products without the use of the food container  16 . In such a configuration, the food products within the second compartment  20  would be sealed in the compartment by a removable lid placed over the top of the second compartment. The removable lid could be a full-panel pull off, a foil lid adhesively attached to the top surface of the second compartment, a lid removable by a standard can-opener or other suitable lid.  
         [0038]     The food container  16  may have one or more partitions to create two or more food compartments. In this way, the thermic module  14  can be configured to heat each food compartment at different heat levels, including little or no heat at all to one or more of the compartments.  
         [0039]     The thermic module  14  has two reactant chambers. The thermic module  14  is shown separately from the assembly  10  in  FIGS. 8 and 9 . The first reactant chamber  30  contains a first reactant  62  that is physically separated from a second reactant  64  contained in a second reactant chamber  32 . The thermic module  14  comprises a dome-shaped body  34 . The actuator button  38  is disposed at the bottom outer surface of the body  34 . The walls of the body  34  extend radially outward from the actuator button  38  in a wavy surface  36 . The wavy surface  36  makes the bottom of the body  34  relatively flexible so that the actuator button  38  can be pushed inwardly to actuate the thermic module  14 . The actuator button  38  is accessible through the hole  22 . A tamper-evident seal  58  is attached to the bottom surface  24  and covers the hole  22  such that the seal  58  must be removed or damaged to actuate the button  38 . The tamper-evident seal  58  may be a foil decal adhesively attached to the bottom surface  24 .  
         [0040]     First reactant chamber walls  40  extend upwardly from the outer edge of the wavy surface  36  to form the upper boundary of the first reactant chamber. Outer walls  48  extend upwardly and radially in a stepped configuration from the first reactant chamber walls  40  to form the side perimeter of the second reactant chamber  32 . The outer walls  48  may extend just to the bottom surface of the food container  16  or they may extend further up the side of the food container to provide heating on the sides of the food container  16  in addition to the bottom of the food container  16 .  
         [0041]     A plurality of cylindrical prongs  44  with elongated notches  46  are provided on the interior surface of the body  34  in the area of the wavy surface  36 . A breakable reactant barrier  42  is provided at the top of the first reactant chamber walls  40  to separate the first reactant chamber  30  from the second reactant chamber  32 . In general, one of the reactants is a liquid, such as water, and the other reactant is in a solid powdered or granular form, such as calcium oxide. The reactant barrier  42  may be made of foil and may be attached using adhesive or other suitable means. While the reactant barrier  42  may be adhesively attached to just the top annular surface of the first reactant chamber walls  40 , it is preferable that the reactant barrier  42  extend over edge and down the side of the outside surface of the walls  40 . Attaching the barrier  42  to the outside surface of the walls  40  creates a much stronger adhesive seal by increasing the shear strength of the bond.  
         [0042]     A top surface  49  is provided at the top of the outer walls  48  to seal the second reactant chamber. The top surface  49  may be made of foil and may be attached to the outer walls  48  by adhesive or other suitable method. One or more vent holes  50  may be provided in the wall of either the first or second reactant chambers to provide a path through which gas can escape during the reaction to relieve the pressure within the first and second reactant chambers  30  and  32 . The gas flows through the vent holes  50  and into an air space  52  between the body  34  of the thermic module  14  and the container body  12 . This hot gas helps heat the sides of the second compartment  20  which in turn helps heat the food container  16 . The large surface area of the container body  12  which is in contact with the cooler ambient air cools the steam thereby reducing the gas pressure.  
         [0043]     The thermic module  14  may have a ring-shaped detent  66  for receiving a lip  68  of the container body  12  for retaining the thermic module in the container body  12 . The thermic module  14  simply snaps into the container body  12  and the interference between the detent  66  and the lip  68  holds the thermic module in place. Alternatively, the thermic module  14  can be attached to the container body  12  by an adhesive, by ultrasonic or spin welding or by any other suitable method.  
         [0044]     The food container  16  has a bottom surface  54  and a top surface  56 . The food container  16  is shown separately from the assembly  10  in  FIGS. 10 and 11 . The bottom surface  16  is pressed against the top surface  49  in order to make a good thermal connection between the second reactant chamber  32  and the food container  16 . The top surface of the food container  16  has a removable closure  60 . The removable closure  60  is preferably removable as a full panel pull-off or by using a standard can opener. A full panel pull-off typically comprises a closure with a weakened region in the shape of the desired opening along which a pull-off lid breaks away from the remainder of the top surface  56 . Alternatively, the closure a pop tab closure (e.g. the closure on a soft-drink aluminum can) or other removable lid which can be removed to access the food product contained in the food container  16 .  
         [0045]     The preparation of the self-heating tray  10  can be done in several ways. The food container  16  can be snapped or attached into the second compartment  20  after the tray  10  has gone through a retort process. Alternatively, an unfilled food container  16  can be placed into the second compartment  20  and the assembly can be sterilized in a retort process. Then the food container  16  can be filled and sealed. In still another process, the filled food container  16  can be installed in the tray  10  and then the entire assembly can be subjected to a retort process.  
         [0046]     The use of the self-heating tray  10  is as follows. First, the user removes the tamper-evident seal  58  to expose the actuator button  38 . The user depresses the actuator button  38  by pushing it inward. As noted above, the actuator button  38  is coupled to the flexible wavy surface  36  so that the wavy surface  36  resiliently deflects to allow the button  38  to move inwardly. The force exerted upon outer actuator button  38  urges the prongs  44  into the reactant barrier  42 . The prongs  44  puncture the reactant barrier  42  which allows the first reactant in the first reactant chamber  30  to mix with the second reactant in the second reactant chamber  32 . In general, the first reactant is a liquid which flows through the punctured reactant barrier  42  into the second reaction chamber  32  containing a solid reactant. The notches  46  in the prongs  44  facilitate the flow of the liquid reactant into the second reaction chamber  32 . The resulting-exothermic reaction produces heat, which is transferred to the food container  16  by conduction through the top surface  49  to the food container  16 . As noted above, in other embodiments of the invention, other reactants may be selected that give rise to an endothermic reaction when mixed.  
         [0047]     Gas or steam produced in the reaction escapes the reaction chambers  30  and  32  through vent holes  50 . The hot gas or steam flows through the vent holes  50  and into an air space  52  between the body  34  of the thermic module  14  and the container body  12 . This hot gas helps heat the sides of the second compartment  20  which in turn helps heat the food container  16 . The large surface area of the container body  12  which is in contact with the cooler ambient air cools the steam thereby reducing the gas pressure.  
         [0048]     The user can then invert the tray  10  and wait until the reaction heats the food in the food container  16 , which typically occurs within about seven to ten minutes in a tray having a capacity of four to sixteen ounces of food. When the food is heated to the temperature at which it is to be consumed, the user removes the closure  60  giving access to the food contained within the food container  16 . The heated food may be consumed directly out of the food container  16  or it may be removed and placed into or onto a plate or dish).  
         [0049]     One of the reactants  62  or  64  may comprise specially designed calcium oxide particles. There are several characteristics of calcium oxide particles which will effect their reaction with the water. For example, varying the characteristics of the calcium oxide particles can affect such reaction attributes as volatility, rate of the reaction, and total amount of energy obtained from the reaction. Based on these characteristics, specific calcium oxide particles can be designed and produced to attain the desired overall reaction properties.  
         [0050]     The porosity of the calcium oxide particles can greatly effect how volatile a particle will react when water is added. The processing of calcium oxide involves cooking it at 1000 degrees Fahrenheit which drives off moisture and gases that are naturally found in the material. This release creates pores in the material. The cooking time can be increased to a point where the pores will start to close back up in a process call a hard burn. By subjecting the particles to a proper amount of hard burn, the volatility of the reaction with water can be reduced to a more desirable level.  
         [0051]     The size of the calcium oxide particles has an effect on how reactive that particle is. A group of small particles has more surface area that one large particle of equal weight. The greater the surface area, the faster and more thorough the particle will react when mixed with water.  FIGS. 6-9  show transient temperature curves for particles of various sieve sizes ranging from a ¼ inch mesh (largest particle) through sieve #30 (smallest particle). In general, the curves show that smaller particles will heat up faster and also attain a higher maximum temperature. Accordingly, particles of various sizes may be chosen to produce the desired heating profile for the specific application for the container  100 . For an application such as heating solid or semi-solid foods, a preferred distribution of particles sizes is:  
                                                   Particle Size (mesh)   Amount (%)                           #7   2% maximum           #14   80% +/− 5%           #20   15% +/− 5%           Finer than #20   3% maximum                      
 
         [0052]     Another preferred distribution of particle sizes is:  
                                                   Particle Size (mesh)   Amount (%)                           filter thru #7   80% +/− 5%           filter thru #20   15% +/− 5%           filter thru finer than #14   3% maximum                      
 
         [0053]     In still another preferred distribution of particle sizes, 100% of the particles filter through a #7 mesh and are captured by a #14 mesh.  
         [0054]     Additives can also be added to the calcium oxide to increase or decrease the reaction rate. The additives work by several different methods, including chemically, mechanically, or physically altering the interface of the calcium oxide with the water. One of the most important characteristics effecting the reaction is the reaction ratio, i.e. the ration of the calcium oxide to water. Different reaction/temperature curves can be obtained by varying the ratio of calcium oxide to water. For example, it is possible to maximize the peak energy produced by any one size of particle or porosity of a particle. The ratio can also be altered to slightly increase or decrease the overall rate of the reaction. The graphs of  FIGS. 10-11  show the reaction/temperature curves for various ratios of water to calcium oxide. It can be seen that increasing the amount of water to 1.15 parts per 4 parts calcium oxide by mass (i.e. +15% H 20 in  FIG. 20 ), the fastest reaction is obtained and also the most energy of the ratios tested.  
         [0055]     The water comprising the other reactant  132  or  138  may also be modified to optimize its use in the present invention. For example, the water quality is a critical component. Any chlorine in the water may cause the breakable barrier  130  to corrode and fail. Minute deviations in water quality can adversely affect the thermal reaction with the calcium oxide. Trace mineral components in the water should not exceed the concentrations shown on the table in  FIG. 12 .  
         [0056]     Additives may also be added to the water to modify the reaction and improve the compatibility of the water with the other materials of the container. A list of possible additives and their properties is included in the table of  FIG. 13 .