Self-contained immersion exothermic fuel charge
United States Patent 1 Pava [451 Apr. 1, 1975 SELF -CONTAINED IMMERSION EXOTHERMIC FUEL CHARGE [76] Inventor: Thurman Pava, 126 Woodside Ter.,  
 Springfield, Mass. 01108 [22] Filed: July 10, 1974 211 Appl. No.: 486,951  
 [52] U.S. Cl 126/263, 126/367, 44/38, 252/70 [51] Int. Cl F24j l/00 [58] Field of Search 126/367, 263; 149/15, 16; 44/38, 40; 252/70 [56] References Cited UNITED STATES PATENTS 2,953,443 9/1960 Lloyd 44/3 3,527,201 9/1970 Epstein 126/263 12/1970 La Rocca 149/15 5/1974 Olson 126/263 Primary Eraminer-Carroll B. Dority. .lr. Assistant Examiner-Larry l. Schwartz Attorney, Agent, or Firm-Chapin, Neal and Dempsey [5 7] ABSTRACT An immersion heater having a combustible heating charge in helical tubular form. The heating charge is form-stable and constituted of a combustible composition in unitary helical configuration. A refractory material is interposed between each convolution of the heat generating helix. In the preferred form of the invention, the heating charge is bonded to the inner wall of a tubular receptacle for immersion in a medium to be heated in its container.  
 6 Claims, 3 Drawing Figures WENT 1197s 3, 874,365  
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 SELF-CONTAINED IMMERSION EXOTHERMIC FUEL CHARGE BACKGROUND For a number of years attempts have been made to produce a solid fuel charge for use as an immersion heater capable of heating beverages or foods in the container in which they are packaged so as to provide a convenient, safe, reliable, inexpensive self-heating package which will meet with wide market approval.  
  A number of suitable combustible compositions containing their own source of oxygen have been provided for such immersion heaters. These are disclosed in numerous prior art patents, including U.S. Pat. Nos. 802,256, 2,384,278, 2,388,466, 2,953,443, 3,527,021 and British Pat. Nos. 8642 of l9l5 and 8l6,5l2.  
  In general, the approach heretofore utilized in such seltheating containers was to heat the outside walls of the container. This approach proved too slow and too expensive and the containers were generally too heavy and too bulky.  
  Another significant approach was to use an immersion heater, and while this proved to be advantageous from the standpoint of heating efficiency, the fuel compositions used were generally characterized by too violent or rapid combustion. Attempts to overcome this problem involved the use of heavy fuel holders, heat sinks and the construction of special heating chambers divided by partitions to slow combustion. In addition, various exothermic compositions were used in an at tempt to provide controlled burning. None ofthese approaches for one reason or another was found entirely acceptable in the market place.  
  The principal object of this invention is to provide an immersion type heater which is safe, reliable, compact, easy to use and relatively inexpensive to produce.  
  Another object of this invention is to provide a food or beverage package with a built-in self-contained heater so that the contents of the container can be completely heated anywhere indoors or outdoors to provide a convenient hot meal or beverage without the need of any utensiles or heating equipment.  
  A further object of this invention is to provide a food or beverage container of the above type constructed so that in order to initiate combustion one must of necessity vent the container to prevent pressure buildup from heating the contents of the container.  
  The above and other objects and advantages of this invention will be more readily apparent from the following description and drawing, in which:  
  FIG. I is a perspective view partially in section of a type of beverage container embodying the invention;  
  FIG. 2 is a cross sectional view showing the immersion heating element removed from the container of FIG. I; and  
 FIG. 3 is a section taken along line 33 of FIG. 2.  
  Referring now in detail to the drawing, in FIG. 1 is shown a can or container 4, such as a sealed cylindrical receptacle, which may be fabricated of any suitable material, such as metal or plastic and may be an ordinary tin plated food or beverage container in which foods and beverages are hermetically sealed for preservation, shipment and marketing. A sleeve of insulating material is shown about the circumference of the container 4 and serves to insulate the container against too rapid heat transfer from the contents of the container. Moreover. the sleeve enables handling ofthe container without danger of the user being burned, even though its contents are hot. Thesleeve may be any suitable insulating material, including polystyrene foam, corrugated fibrous sheet material or the like and may be perforated to enable safe handling, while at the same time providing good heat transfer from the metal container should the heating composition be ignited when the container is empty. A sleeve is shown at 6.  
  In the embodiment shown, the container 4 is filled with a supply of liquid 8 which is to be heated by the immersion heater shown generally at 1&#39;0. The immersion heater 10 comprises an upwardly opening cylindrical tube 12 having a closed lower end. At its upper end the tube has an outwardly extending flange 13 which forms or is joined to the top wall of the container 4. A pair of ports or holes 14 are provided through the top wall 13 of the container to provide means for venting the container to prevent excess pressure buildup when the liquid 8 is being heated. A closure .member&#39;or cap 16 is fitted into the upper end of the tube 12 and includes a central aperture 18 through which extends the upper end of an igniter strip or fuse 20. The lower end of the fuse 20 terminates in an igniter head 22 engaged with a solid combustible fuel charge 24 disposed within the tube 12. A suitable gas permeable refractory insulation 25 may be packed around the fuse 20 and igniter 22 to secure the latter in place within the heater tube 12 and serves as a flame suppressor and smoke filter.  
  A closure strip 26, which may be fabricated of any suitable material, such as plastic or metal foil having its undersurface coated with a suitable adhesive or bonding agent, removable seals over the vents l4 and also over the upper end of the fuse 20. The vent ports are disposed on diametrically opposite sides of the hole 18 in the upper end of the heater tube 12. Therefore, to uncover the fuse 20 one necessarily also uncovers the ports 14. This safety feature prevents ignition of the fuse strip 20 without venting the container to the atmosphere, thereby preventing pressure buildup in the co ntainer as a result of heating its contents. v I  
  The heating charge 24, best seen in FIGS. 2 and 3, is in the form of a cylindrical tube having a central bore 28 extending therethrough from end-to-end. The charge, while integral, is composed of two interfitted or mating helices, one axially offsetfrom the other. The outer helix 30, in an axial direction, is a solid, integral fuel train in helical configuration with each convolution thereof separated from the adjacent convolution by a convolution of a skeleton or inner helix 3 2. The inner helix is also in unitary form and composed of a suitable refractory material which will prevent combustion in one layer of the fuel train from advancing linearly in an axial direction of the charge. .As a consequence, combustion, which starts at the igniter 22, will follow a helical path, starting at one end of the fuel train and advance continuously to the other end.  
  Preferably fuel charge 24 is retained in fixed location in the tube 12 in uniformly spaced relation with respect to the inner surface of the tube. This is achieved by a thin layer 34 of refractory mortar or sand bonded to the inner wall of the tube. The refractory layer 34 provides a insulating barrier layer which protects the thin metal tube 12 against becoming overheated from direct Contact with the Thermit&#39;- mixture. In addition, the layer 34 serves to retain the fuel charge 24 in fixed position within the tube 12.  
  The fuel charge 24, embodying this invention, burns at a controlled rate so that the maximum temperature encountered at any point within the tube 12 is maintained well below the melting point of the tube. Indeed, when a fuel helix as described was burned in a steel fuel holder or tube I2 surrounded by air at room temperature, having a wall thickness of 0.01 inch and the wall coated with a thin layer of refractory material 34, the fuel holder did not melt. As a result, it has been found that relatively low cost, highly exothermic materials can be safely used in combination with low cost, light weight, thin wall fuel holders.  
  The fuel charge 24 may be fabricated in any suitable manner, such as by feeding alternate layers of the combustible mixture which will form the layers of the helix 30 and the refractory mixture which will form the layers of the helix 32 into a rotating mold or directly into the fuel holder.  
  The refractory skeleton 32 may be formed of any suitable material which will retain its helical configuration and be ofsufficient integrity to support the burning convolutions of the fuel helix and insulate one convolution of the fuel train from the other so that direct axial transgression of combustion from layer to layer is prevented. The refractory convolutions of the skeleton 32 may be formed of any suitable material to provide such insulation, including refractory mortar or sand with suitable binder of sodium silicate to insure form stability of the helix 32.  
  The fuel helix 30 embodying this invention may be a mixture of iron oxide, aluminum, widely known as Thermit and inert filler, such as sand, with a sodium silicate to bond the other constituents into helical cylindrical tubular configuration. The amount of inert filler, such as sand, and selection of its particle size from fine to coarse are variables which may be controlled to achieve the desired combustion rate. Using a fuel charge made in accordance with this invention. the combustible helix 30 supported by the refractory skeleton helix 32 will retain its helical configuration throughout the combustion during which the Thermit mixture reacts with very high temperatures over 3()()() F. The fuel charge 10 is thus characterized as form stable prior to, during and after combustion, thereby pre venting agglomeration of molten residue or slag which might tend to concentrate heat at one location in tube .12. This is an important safety factor, especially if the container is empty, as in the case of a defective container from which the liquid contents have leaked out. Even in this unusual situation, the heater embodying this invention will not pose a danger to the user.  
  To use, the sealing or closure strip 26 is simply grasped at one end and peeled from the top of the container. In so doing, the fuse 20 is exposed and simultaneously the ports I4 are uncovered, thus venting the contents of the container. The fuse 20 may then be ignited by any ordinary match, cigarette lighter or the like. The igniter 22, which may be in the nature of an enlarged match head will also be ignited and cause the upper end of the fuel train helix 30 to commence combustion. Burning will advance helically around the fuel charge at a controlled rate so that the contents of the container will be rapidly but safety heated. Since the immersion heater I0 is disposed generally in the center of the container, efficient heat transfer to the contents is achieved. Any steam evolved will be vented by ports 14. During combustion, the bore 28 serves to vent the burning fuel charge through the port I8 provided in the cap 16.  
  During and after combustion the combustible helix retains its helical form and remains fixed in place in the fuel holder 12. As a result, when the contents of the container is liquid, boiling will occur in a very short time without danger of excessively high temperatures melting the relatively thin wall forming the fuel holder 12. When the liquid has been heated, it may be poured into a suitable serving vessel, using one of the vent ports 14. If the liquid is water, it may be used for making instant soup, coffee, tea or other beverage.  
  Having thus described my invention, what is claimed is:  
  l. Immersion heater comprising a heating charge, including a combustible mixture ofunitary helical configuration and a refractory material interposed betweenadjacent convolutions of the combustible mixture, said heating charge being of tubular cross section from en to end and disposed within a receptacle.  
  2. Immersion heater as set forth in claim 1 in which said heating charge is form stable during and after combustion.  
  3. Immersion heater as set forth in claim 2 in which said receptacle is tubular and said heating charge is bonded to the inner wall of said receptacle and being spaced therefrom by a layer of refractory material.  
  4. Immersion heater as set forth in claim 2 in which said combustible mixture is composed of a mixture of iron oxide, aluminum, refractory filler and a binder to hold the constituents thereof in said form stable condition during and after combustible reaction of the mixture and in which said refractory material is in helical form and serves as a skeleton for the combustible mixture.  
  5. Immersion heater as set forth in claim 3 in which igniter&#34; means is provided for igniting said combustible mixture, said igniting means including a fuse extending outwardly of said tubular receptacle.  
  6. Immersion heater as set forth in claim 5 in which said heater is disposed within a sealed container for holding a beverage or food to be heated, said container having vent means opening through the top wall thereof, and a sealing strip removably bonded to the top wall of said container sealing said vent means and preventing access to said fuse whereby removal of said sealing strip provides access to said fuse and simultaneously vents said container.