Abstract:
A heater device includes a container formed from a vapor impervious material and having a quantity of heat generating material therein. Also provided is an activation material proximate the container. A seal on the container is adapted to be opened to transfer the activation material into contact with the heat generating material to generate heat and be resealed to contain the reaction products generating the heat.

Description:
BACKGROUND 
       [0001]    This invention relates to a device for heating the contents of a container and for keeping it warm. More particularly, the invention relates to a self-contained heater device that allows the contents such as food in a container to be heated. 
         [0002]    Often times, it is desirable to heat food and other items at a location remote from a source of heat such as a stove or oven. Other times it is desirable to take warmed or hot food and other items from the place of heating to another location, such as a picnic, school or church basement, scout meeting and any of the myriad of events that do not meet or gather where heat is available. Sometimes the location is in a location where fire is not permitted, such as a class room or outdoors during the dry season. It is also important for military personnel to have access to warm food, particularly when deployed in locations remote from their base or station. 
         [0003]    One such self-contained warmer is disclosed in U.S. Patent Application Publication No. US 2007/0034202, to Punphrey et al. in which a container with an exothermic composition is used to heat a vessel. A membrane is used to cover the exothermic composition, which is then activated by removal of the membrane. Various compositions are disclosed that are based on iron oxidation chemistry. The heater is in direct contact with the container and must be put on a heat-resistant surface to be used without damage. 
         [0004]    U.S. Pat. No. 6,705,309 discloses a self-heating or self-cooling container in which tubular walls defining an internal cavity into which steam or hot air is placed as a source of heat. This, of course, requires a source of that heated material. 
         [0005]    Other heater devices for food generate heat by chemical reaction, and in so doing generate hot gases, steam or hot water vapor, which is potentially hazardous to the user and which may, in some instances, contribute to pollution of the environment. 
         [0006]    It would be a great advantage if a way of heating containers could be developed that has a controlled release of heat that is within acceptable safety limits. 
         [0007]    Another advantage would be to provide a way of heating containers that produces heat over an extended period of time, rather than simply having an exothermic reaction that lasts a few minutes or less. 
         [0008]    Yet another advantage would be to provide a way to generate heat by an exothermic reaction without releasing any gas, steam or hot water vapor to outside the device. 
         [0009]    Other advantages will appear hereinafter. 
       SUMMARY 
       [0010]    The unique aspect of this invention is that a controlled, dispersed exothermic reaction can be used to heat or cook the contents of a container quickly and effectively while maintaining the heat for an extended period of time without releasing any of the reaction products to outside of the device. 
         [0011]    It its simplest form, the invention comprises a container or pouch that contains a quantity of heat generating material that can be activated by the addition of an activation agent. The container or pouch includes a removable seal at one end that can be opened to add the activation agent and a seal that can be closed once the activation agent has been added to contain steam, vapor or other reaction products. 
         [0012]    In the preferred embodiment, the removable seal and the seal to re-close the end can be the same seal, such as like those found on Ziplock® brand food storage bags, manufactured and sold by S.C. Johnson &amp; Sons, Inc. Such seals include Alternatively and also preferred are removable seals that can be pulled or torn off, with or without score lines to assist in its removal, and are-able to be re-closed. A zipper that is vapor tight is also useable. The function of the seal or seals is to prevent moisture from entering the pouch until activation is desired and then to contain any vapor, steam or other gas that might be generated during the activation of the heat generating material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a schematic view of one embodiment of this invention. 
           [0014]      FIG. 2  is a schematic view of a second component of the embodiment in  FIG. 1 . 
           [0015]      FIG. 3  is a schematic view of another embodiment of this invention. 
           [0016]      FIG. 4  is a schematic view an embodiment in a package. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    The heater device of this invention is shown generally in  FIGS. 1 and 2 . The device includes a container or pouch  11  formed from a vapor impervious material. Preferred is a container  11  made from Aclar®, which is a polychlorotrifluoroethylene (PCTFE) material manufactured and sold by Honeywell International Inc. A clear film is crystal clear, biochemically inert, chemical-resistant, nonflammable, and plasticizer- and stabilizer-free. Aclar laminates provide a wide range of gauges and thus barrier levels to allow flexibility in selecting the optimum barrier level for the chemical system chosen. Other similar pouch materials may be used as well. All that is required is that the material has a functional moisture and vapor barrier for the other components of the invention. The container  11  includes a quantity of heat generating materials  13 , described in detail herein below. 
         [0018]    The heat generating materials are activated once the device has been placed proximate an object to be heated by opening seal  15  and adding a quantity of an activation agent, followed by quickly closing the seal  15  to contain any reaction products such as steam, other vapors, and the like. 
         [0019]    In a preferred embodiment, seal  15  includes a pair of elongated mating strips across the top of the container, wherein one strip has a tongue disposed thereon and the other strip includes a mating groove thereon, wherein the tongue and groove engage to form a seal and disengage to open. This is often described as a “zip lock” seal. Ziploc® is a brand of disposable, re-sealable zipper storage bags and containers originally developed by Dow Chemical Company, and now produced by S. C. Johnson &amp; Son. According to Dow&#39;s website, the bags were originally test marketed in 1968. The bags and containers come in different sizes for use with different products. The brand offers sandwich bags, snack bags and other bags for various purposes. 
         [0020]    In  FIG. 2 , a second container  17  contains an activation agent  19 , described in detail below, that is accessed by removing the top of second container  17 , such as by pulling the top so that gap  21  starts a tear alone the line extending from gap  21 . 
         [0021]      FIG. 3  illustrates an alternative embodiment where container  31  is similar to bag  11  with a heat activation material  13  inside. The seal in  FIG. 3  includes a tear tab  35  that moves along container end  36  to provide access to container  31 . Once the activation agent has been added, a second seal  37  is closed. Seal  37  may be similar to seal  15  of  FIG. 1 , with or without the tab portion. 
         [0022]      FIG. 4  illustrates the use of this invention with a box  41  that contains food or other material that is to be heated. Typical food boxes  43  and  45  are what is known in the military as MRE, which is an acronym for “meals ready to eat.” A heater  47  of the type shown in  FIGS. 1 and 3  is placed proximate the boxes  43  and  45 , and seals  15  or  35  or the like are opened and an activation agent is placed inside container  47  and the seal  15  or  37  is closed as described above. 
         [0023]    There are a number of combinations of heat generating materials and activating agents that are suitable for use in the present invention. The selection of specific components is to be based upon cost, compatibility, ease of control of the exotherm, and other factors. 
         [0024]    The preferred activating material of this invention is water. This is plentiful and safe, and reacts with a number of materials to produce an exothermic reaction. 
         [0025]    The preferred heat generating material is a solid formed from several components that, when free from moisture, are stable for up to three to five years or more, and which react when moisture is present to generate heat. The preferred solid is made from crystalline calcium oxide, a zeolite powder, and a polyalkyl glycol such as polyethylene glycol. The amount of activation material, such as water, is preferably from about 75 to 125 weight percent, based upon the total weight of heat generating material. Approximately equal amounts by weight of water and heat generating material is the preferred ratio. 
         [0026]    The amount of calcium oxide ranges from about 30 to 70 weight percent, the amount of polyethylene glycol ranges from about 15 to about 35 weight percent, and the amount of zeolite ranges from about 15 to about 35 weight percent, based on the total weight of heat generating material. Preferred is about 25 weight percent each of the polyethylene glycol and zeolite and about 50 weight percent calcium oxide. 
         [0027]    The heat generation material most preferred, using the above components includes a calcined calcium oxide. This material is available as a small particle size, with a diameter less than about 0.2 mm, and as a particle of somewhere between 0.2 and 0.8 mm. Larger particles are ground and smaller ones sieved, and the calcium oxide is then calcined. It has been found to be effective to calcine for at least 60 to 120 minutes, and preferably about 90 minutes, at temperatures above 500° C., and most preferably at about 550° C. for that period of time. The calcined calcium oxide is, of course, desiccated to prevent any contamination by moisture. 
         [0028]    More than 150 zeolite types have been synthesized and 48 naturally occurring zeolites are known. They are basically hydrated alumino-silicate minerals with an “open” structure that can accommodate a wide variety of positive ions, such as Na+, K+, Ca 2 +, Mg 2 + and others. These positive ions are rather loosely held and can readily be exchanged for others in a contact solution. Some of the more common mineral zeolites are: analcime, chabazite, heulandite, natrolite, phillipsite, and stilbite. An example mineral formula is: Na 2 Al 2 Si 3 O 10 -16H 2 O. Zeolites, by their nature, are finely porous structures that are “hungry” for water and that have the ability to hold heat. In the present invention, the activation agent, water in the preferred embodiment, enters into the zeolite pores, trapping the water as it is heated by reacting with the calcium oxide, thus storing heat, providing a longer, more evenly distributed supply of useable heat. 
         [0029]    The polyethylene glycol component of the heat generating material is admixed with the calcium oxide and zeolite and placed in the outer container as described above. When the activation agent, water, is introduced into the heat generating material, the polyethylene glycol coats the calcium oxide and zeolite, further delaying the exothermic reaction between calcium oxide and water, and adding to the utility of this invention. 
         [0030]    The present invention provides a significant advantage over the prior art in several ways. Because the outer container is sealed, as described above, the exothermic reaction when heat is generated does not release steam or other vapor as do presently available heaters. In addition, the heater device of this invention is much more effective that what has been done in the past. The heater of this invention has been used to heat products to 150° F. within 5 minutes and maintained the heat at or above 140° F. for 50 minutes. Prior art devices take 12 minutes to reach only 140° F. and only hold that temperature for 20 minutes. 
         [0031]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.