US2620788A

US2620788A - Self-heating container

Info

Publication number: US2620788A
Application number: US193868A
Authority: US
Inventors: Eugene J Rivoche; Sukacev Lev
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-11-03
Filing date: 1950-11-03
Publication date: 1952-12-09
Anticipated expiration: 1969-12-09

Description

Dec. 9, 1952 E. J. RlvocHE ET AL 2,620,788

SELF-HEATING CONTAINER Filed Nov. 5, 1950 3 Sheets-Sheet l /9 @ww QQQQQQ@ 27 @QQ/9@ I @QQ/99@ Q EUGENE J- 11, N n l b l H N ,f mw ATTORNEYS Dec. 9, 1952 Filed Nov. 5, 1950 E. J. RlvocHE ET AL 2,620,788

SELF-HEATING CONTAINER 3 SheeLS-Sheetl 2 Dec. 9, 1952 E. J. RlvocHE ET AL 2,620,788

SELF-HEATING CONTAINER Filed NOV. 5, 1950 5 Sheets-Sheet 5 INVENTORS G. u@ Rn/@CHE F1 9 E fgwv ATTORNEYS Patented Dec. 9, 1952 SELF-HEATING CONTAINER Eugene J. Rivoche and Lev Sukacev, Washington, D. C.

Application November 3, 1950, Serial No. 193,868

36 Claims. l

This invention relates to self-heating containers for the packaging of foods or other materials which it may be desired to heat without recourse to extraneous heating agents. Such containers are particularly adapted for emergency use by the Armed Forces and others under conditions where it is impossible or impractical to prepare hot foods under the usual conditions.

The self-heating containers of the present invention embody improvements on the type of self-heating container disclosed in the application filed by Lev Sukacev on June 28, 1950, Serial No, 170,757. In that application there is disclosed and claimed a self-heating container in which the container for the foods which it is desired to heat is mounted for telescopic movement in an outer supplemental container, and lime or other material, which on reaction with water liberates heat and in doing so expands in volume, is interposed between the bottom of the food container and the outer supplemental container. The telescopic mounting of the food container within the outer container permits expansion of the lime when water is added without subjecting either container to excessive pressure, and thereby makes it possible to construct both containers of relatively light-weight material.

An important consideration in any self-heating container is the eiiiciency of the transfer ol" heat from the exothermic material to the food container, particularly if the container may be used in cold climates where the heat necessary to bring the food to the desired temperature is greater, and where dissipation of liberated heat may be greater than otherwise.

As the amount of exothermic material needed to bring the food of the container to the desired temperature is vinversely proportional to the efliciency of heat transfer thereto from the exothermic material, a high heat transfer eiciency permits the use of less of the exothermic material, as well as making it possible to use a smaller container, an important factor where transportation space is of importance.

When water is added to burnt lime, the resulting exothermic reaction, or slaking, causes the body of lime to swell or expand, if unrestrained, to approximately three times its original size. The expanding or swelling of the lime reduces the heat conductivity thereof by as much as 90 to 95%.

When the exothermic material is lime or other material which expands appreciably whenv Cil water is added to it, some expansion is desirable in order that it shall not be necessary to use materials for the container which will be strong enough to resist the entire pressure developed by the expanding exothermic material. but unlimited expansion is not desirable since it too greatly reduces conduction of heat to the food container. Consequently, one of the features of the present invention is to provide a self-heating container of the type disclosed in the aforesaid application in which the food container has only a limited outward movement relative to the outer container, with the outward movement being stopped when the slaking lime has expanded to from about one and onehalf to two and one-half times its original volume, and before it has reached its normal unrestrained expansion. Adv'antageously, the outward movement of the food container may be stopped when the lime has expanded to about twice its original volume. By thus permitting a partial expansion only of the lime, the lime will be maintained in a somewhat compressed, more dense state, and its heat conductivity will be much greater than that of the lime in its fully-expanded state. Also, as the bottom of the food container is the restraining force on the expanding lime, the lime will cause a good heat-conductive contact to be made with the food container, which also enhances the conduction of heat from the lime to that container. The fact that neither the food container nor the outer supplemental container has to resist the full expansive force of the lime permits the use of relatively light material for construction of both of those containers, and thereby lessens the cost of the self-heating container. The present invention further provides for increased conduction of heat from the exothermic material to the food container by providing metal, or other elements of good heat-conducting properties which, throughout all stages of expansion of the lime, are maintained in contact with the body of lime and the food container and act as conductive paths for transferring heat from the hot lime to the food container.

The dissipation of heat from the exothermic material, other than to the food container to be heated, is prevented, or largely retarded, by suitable insulating means, and by enclosing the entire self-heating container in an enclosingpcasing of cardboard or other material Lhaving relativelyA good insulating properties which insulates it from the surrounding atmosphere and also prevents air-currents from picking up heat both from the food container and the outer supplemental container.

Whereas the self-heating container of the foresaid application included a receptacle for water to be added to the exothermic material, the container of the present invention is packaged dry, that is, without Water to be added to the exothermic material, and special means are provided to facilitate the addition of Water and also to assure that the proper amount of water to liberate the maximum heat from the exothermic material is added.

Other features of the invention will be clear from the following more detailed description taken in connection with the accompanying drawings. However, it is to be understood that such further description is by. Way of exemplication and the invention is not limited thereby, except to the extent set forth in the appended claims.

In the drawings:

Fig. 1 is a vertical cross-sectional viewv o f a self-heating container embodying the invention.

and enclosed. in an insulating casing,

Fig. 2 is a View similar to,y Fig. 1 showing the relative position of the partsafter the exothermic material has expanded on reaction with water,

Fig. 3 is a vertical sectionalI view of the lower portionv of the self-heating container removed from its insulating casing and showing the manner in which water is retained on the bottom ofthe outer supplemental containerfor; passage to the exothermic material,

Fig. 4 is a horizontal cross-sectional. view, partly broken away, on line 3.--3v of Fig. 1,

Fig. 5 is a perspective view, with parts broken away, of one of the expansible containers for the exothermic material,

Fig. 6. is a vertical cross-sectional view of a modified form of a self-heating container embodying the invention, with the` insulatingA casing removed, g

Fig. 7 is. a horizontal cross-sectional View on line 1 1 of Fig. 6,

Fig. 8 is a vertical cross-sectional view. of a self-heating container having a space| withiny the outer confines ofthel food container for thez exothermic material, also shown withv theA outer insulating casing removed, and

Fig. 9 is a vertical cross-sectionalz view ofa self-heating container embodying the invention and particularly adapted for the thawing and heating of frozen foods, removed from itsouter insulating container.

Referring now tol the drawings, and. first to the form of the invention shown in Figs. 1 to 5, the material which isA packed for subsequent heating, hereinafter referred to. as food but which may be, material ofl any kind, ishermetically sealed in, a, container I of metal or other material having good heat conductivity, in a,

manner well-known, in the food packaging art. Such containers may be theI usual tinned. or lacquered metal, cans.

The food container l is mounted for subsequent telescopic movement in an outer, openended supplemental' container 2, of' the same shape as the container I and having a, bottom 3 and side wallsv 4. The food container I and the supplemental. container 2, may be of any desired shape and proportions, although normally, a round, relatively flat food containeris preferred. When the food container has relatively little height, the heating of the food therein, in the manner set forth below, as facilitated.

The side walls 4 of the outer container have an inside diameter sufiiciently larger than the outside diameter of the food container to just compensate for the increased diameter caused by the crimped seal 5 at the periphery of the bottom of the food container. Thus, while the food container may move freely within the outer container, the crimped seal 5 lies sufficiently close to the outer container to effectively prevent any appreciable amount of the exothermic material being forced past it.

After the food container has been placed in the outer container 2, the outer free edge of the side walls 4 are bent or curled inwardly to provide an internally-extending flange or projection 6 to form a stop. which on outward movement of the food container is engaged by the crimped seal 5 and thereby limits the outward movement of the food container.

If the food is not packaged in a container having an outwardly-extending crimped seal which can engage the inwardly-extending ange. or projection 6, a suitable outwardly-extending ange or projection should be formed on, the lower portion of the food, container. Such a projection may be in the form of an annular ridge formed by grooving from the inside, as inv a modification to be described later.l or spaced projections formed by indenting from the inside.

For the purpose of heating the food Within the container I, exothermic material 1, that is, a material which will react with water toliberate heat, is placed between the bottom of the food container I and the bottom` of the outer supplemental container. The exothermic ma.- terial may be of any knownmaterial or composition which will react with water to liberate a substantial amount of heat. but we prefer burnt lime as it is readily available, is` cheap, andon reacting with water liberates large amounts of heat.

The exothermic material 1 is placed in sectorshaped receptacles 8 of aluminum or-other metal having good heat-conductiveproperties; Four such containers are used but a lesser or greater number may be used if desired. If the food container is quite large, six or even eight. or more such containers may be used. Each of the sector-shaped receptacles comprises a lowerv tray portion 9 and a cover portionl0 having downwardly-extending side` anges II and I-2which make a sufficiently good contact with the upwardly-extending sidesl I3 ofthe lower trav,v portion to readily conduct heat from the trayK p01'.-

tion to the topof the cover portion. However..

the frictional engagement of the flanges of the cover portion with the side walls of the tray portion is no t such aswill prevent relative movement of the cover and tray portions on expansion of the exothermic material when` reacted4 with water.

The cover portion of each4 of the receptacles for the exothermic material' is contoured to ac,- curately conformto the contour of that portion of the bottom of the food receptacle withwhichit is in contact, so that the: bottom of the-l food container will lie in close, heat-conductive contact with the top of the several receptacles for the exothermic material. When the bottom ofthe food receptacle is reinforced with annular. outwardly-extending grooves or ribs, the several Ireceptacles 8 will haveY aligned' arcuate grooves 5 complementary to such grooves or ribs of the food container.

The top of the cover portions I lpreferably are solid to provide a continuous heat-conduct- `ing surface to the bottom of the food container, although, if desired, one or more openings may be placed in the top of the cover portion to permit direct conta-ct by the lime in the receptacles with the bottom of the food container.

To permit access of the water to the exothermic material. as described later, the bottom of the tray portions are perforated as at I4. The perforations -advantageously are so arranged that continuous straight metallic vpaths for the conduction of heat are provided both to the straight radial walls and to the arcuate outer wall of the tray portions. The perforations advantageously are formed by a punching operation which will leave inwardly-extending flanges or burrs I at the sides of the perforations. Such flanges or bur-rs when the exothermic material .is reacted with water, will assist in tr-ansferring heat from the body of the exothermic material to the metal walls of the lower tray portions.

The straight radial side walls and the outer arcuate walls of the cover portions I 0 are of a depth suilcient to extend below the bottom of the -lower tray porti-on 9, the depth of the outer arcuate Wall is greater than the straight radial side walls, and to accommodate such additional depth the periphery of the bottom of the outer supplement-al container 2 is grooved outwardly as at I6 to provide a trough into which the arcuate outer wall of the cover is received.

The depth of the flanges I I and I2 is such that when the exothermic material has expanded and moved the cover members IU relative to the tray porti-ons 9 the maximum amount permitted by the limiting flange 6, they still will contact the side walls of the tray portions S and provide a good conductive path for the conduction of heat from the exothermic material to the top of the covers and to the bottom of the food container.

In the drawings the flanges of the covers are shown as making a close fitting contact with the outside of the side walls of the tray portions. If desired, the flanges of the covers can be received within and make a close fitting contact with the inside of the side walls of the tray portions.

To further assist in the transfer of heat from the internal portions of the body of reacting exothermic material to the top of the receptacles 8 and from them to the bottom of the food container, a mass of metal shavings or other flexible springy material I1 of high heat conductivity, such as shavings of aluminum, copper, etc., are embedded in the exothermi-c material in each of the receptacles 8. These shavings normally are in the form of a springy mass several times the depth of the receptacle 8 so that when the covers I0 are placed on the tray portions and pushed tothe position shown in Fig. 1, the mass of shavings will be compressed. As the receptacles eX- pand under the expansive force of the reactingr exothermi-c material, the springy mass of shavings II will open up and maintain contact with the covers I0 and form a metallic path for good conduction of heat from the mass of expanded exothermic material to the covers I0 of the receptacles, from which the heat is conducted to the bottom of the food container.

Instead of using a springy mass of metal shavings or the like to conduct heat from the mass of exothermic material to the covers of the receptacles, springs, or flexible members secured to the covers I0 and extending down into the mass of yexothermic material, as disclosed in other embodiments of the invention to be described, may be used.

A layer I8 'of exothermic material of the order of one-tenth inch in thickness is interposed between the bottom of the sector-shaped receptacles 8 and the bottom of the outer container 2 and serves to insulate the receptacles 8 from the container 2 and thereby prevents or greatly retards the passage of heat from the receptacles 8 to the outer container. The .layer I8 also serves to maintain the lower edges of the flanges I I and I2 of the cover portion spaced from the bottom of the :outer container so that they Will not provide a path -for the conduction of heat from the receptacles 8 to the outer container. To further insulate the receptacles 8 from the outer container and thereby further reduce loss of heat, rings I9 of suitable insulating material are interposed -between the arcuate flanges I2 of the several receptacles 8 and the side wall of the outer container.

The exothermic .material normally is maintained hermetically sealed between the food receptacle and the -outer container 2 by a sealing band 20 extending around the side walls of the food container and overlying the upper end of the side Walls of the outer container 2. The sealing band may be an adhesive tape, a strip of plastic, or rubberized, or other appropriate material. The sealing band 20, while adequate to hermetically seal the container, is sufficiently weak to rupture under the expanding force of the ex-othermic material sh-ould its removal be overlooked before the container is put into use. If desired, a metal tape, wire, or band 2I may be wound about the food container and the outer container from top to bottom to give protection against removal of the food container from the outer `container until heating of the material in the food container is desired.

Water is admitted to the exothermic material in the receptacles 8 by punching holes in the bottom of the outer container 2 thro-ugh which it passes. To facilitate the punching of such holes, the bottoms of the receptacles 8 are formed with a series of slight indentations 22. As the selfheating containers are designed primarily for emergency use, or for use where punching tools may not readily be accessible, a nail or other punching tool may be packed in the container for use in making the punch holes for the entry of water.

A gauge ring 23 is mounted about ythe lower portion of the outer co-ntainer 2 and has its inner end 2li turned inwardly to form an inwardly-k extending flange which makes a frictional sliding fit with the side walls of the outer container. Outward movement of the gauge ring is limited by engagement of the inwardly-extending flange 24 with an outwardly-extending projection 25 adjacent the bottom of the outer container. The width of the gauge ring 23 is such that when the ring is moved outward to its maximum extent, and the container inverted, the ring will define a space having a volume equal to the volume of water which should be added to the exothermic material to give the maximum heating eifect.

To further prevent dissipation of heat when the container is being used, it is completely enclosed in an outer casing 26 of cardboard, insulating board, or the like. The casing 26 comprises a lower receptacle 21 and a cover 28 having a depending side wall 29 of suflicient depth to mainasogrss tain: contact with the side wall of the lower.' receptacleY when the foodicontainer'has been raised to the maximum amount permitted by the. limit.- ing ilange 6 under the expansive force exerted by the exothermic material., A sealing strip 20x, similar to .the band 20, may normally secure the cover. 28 in place on the. receptacle 21'..

When the container is. to he used, it is; removed from. the casing 26 and. the retaining band 2l and the. sealing strip; 20x.- are. removed. Thecontainerthenis temporarily inverted, holes punched in the bottom. of the outer receptacle.y for the passage of water toV the exothermicA material, and thev gauge ring 23 lifted to the position shown in Fig. 3. The space enclosed by the gauge rimar 23 is: then filledA with water and the. container left inverteduntil all of the water has passed through theV punch holes in the. bottom of the outer container and into the exothermic material. The

container then is .turned back to its. normal pOstion. with the exothermi'c material at the bottom so that the heat will rise upwardly therefrom in a normal manner and be conducted by the metall-ic conductive path heretofore described to. the food' container. The food container is then opened before its 'becomes too hot, and to permit occasional stirring ofthe food during the heating operation to facilitate4 transfer of heat to all portions thereof, and is replaced in theouter casing 26 and retained thereinuntil` the food in the food container is. thoroughly heated..

The. exothermic material on'. reaction with water puffs or expands; In. the case of burnt lime, the expansion if unrestrained would result in the lime being increased .to approximately three. times its original volume, with a reduction of its normally low heat conductivity by about 90 to. 95%. After thel lime has expanded to approximately two timesl its original volume, the food container will have been lifted to an extent such that the bottom crimped seal 5 engages the inwardly-extending ange 6 of the outer container and further outward movement of the food container is prevented. However, the generation of gas continues and createsy an internal pressure. within the receptacles 8 which forces their covers IU tightly against the bottom of the food container so that a good heat-conductive contact is made.

The engagement of the crimped seal 5 with the flange 6 also takes place before the side flanges l I and l2 are separated from contact with the upwardly-extending side walls of the tray portions 9. Thus, the contacting side walls of the tray and cover portions of the receptacles also provide a good heat-conductive path to the top of the covers in contact with the bottom of thev food container.

As the heat conductivity of the lime progressively decreases on expansion of the lime, the controlling of theextent of the expansion of the lime to less than its normally free expansion also makes the lime itself a better conductor for transferring heat to thev covers and from them to the food containers.

As the lime expands and separates the cover and tra-y portions ofthe receptacles 8,Y the mass of metal shavings I'I which have been maintained under compression during the shipping and storage of the container expands and continues to maintain contact with the undersurface of the cover portions IU and formpaths for good conduction of heat from the interior parts of the lime in each receptacle. The expansion of the limeY also tends to some exten-t toy expand the mass of metal shavings and to cause them to maintain. a goodv heat-conductive contact with the cover portions of the receptacles. H.

The form of self-heatingV containershown in Figsdl and'I Z generally is the same as that dis.- closed; in Figs. 1. to 5 and; comprises a food container 3U, and an. outer. supplemental container 3| having` a. bottom 32 and' sidewalls 33, the outer ends, of. which are curled inwardly to provide. a. flange 34 which,I on. expansion-.of the exothermic material, is. engaged by an outwardly-extending bulge: 35. at the peripheryof the lower portion of the. foodcontainer to limit. further outward move.- ment of that container under the. expansive force of. theV exothermic material'.

The sector-shaped, receptacles 36 for the lime or other exothermic' material are generally similar to.A those of the preceding iiguresand comprise tray portions 31 having side anges 38perforated bottoms 3.9, and cover portions 40 having soli-d tops 4l.- .and'depending sidev flanges 42 which have a close lit with and extend below the. side walls of the. tray portion. Asin the preceding figures, the arcuate outer side flanges of thev covers, which .are of greater depth than the radial side walls. of the; tray portions, are. received in an annular groove or trough 4-3 at the periphery of the bottom of the outer container. However, in this embodiment of the invention the radial side walls of the. trays and the coverportions do not extend quite to the center of the container and do not meet one another. With this arrangement,4 a cen-tralspace 44 is'provided at the. apex oieach of the. sector-shaped receptacles into which water may enter and from which it may passv to. the several. receptacles' through the openings at` their several apices.

This form of the invention is adapted for use with foodv containers which have a concave bot'- tom, and the several receptacles 36 are. curved so that. at least their cover portions. accurately conform to the curvature of the. bottom ofthe food container so. as to make good heat-conductive. contact therewith. The receptacles 36` also are insulated from the. outer container by an insulated layerv ofi lime or other exothermicv ma-` terial 45', and a ring 45" of insulatingy material isv interposed between thel outer flange of the cover portions. 40 and the o uter container tov prevent transfer of heat when the container is put into operation. .f

The depth of the. groove or trough 43 is sutilcient. that', with thevconcave bottom 32 of the outer container, it provides.A a space. adequate, when the container is. inverted, to contain sufl`- cientA water to properly activate the exothermic material in the receptacles 36.

The concave bottom 32v of the outer container is provided with slight indentations to facilitate punching.

Instead of a sealing bandoverlapping the topV edge of the outer container 3l and being secured to.- the sidewalls of the food container, like the band 2u previously described, the exothermic material in the receptacles 3S is hermetically sealed* by a.v metallic cover 48 for the outer container 3f having aside flange 41. suiciently wide that when the, cover i's placed over the outer container with the. fcod container in it, it. will overlap the side walls; of the outer container. Hermetic sealing is obtained by soldering the lower edge of the nange 41 to the side Wall of the outer container with a solder which is suiciently weak to rupture.` under the expansive force of the exothermic material should the cover 46 not. be removed before the, container is put into operation.

Instead of embedding metal shavings in the body of the exothermic material placed in the receptacles to transfer heat from the body of the expanded exothermic material to the covers of the receptacles 36,' each receptacle contains a spring member 48 having a flat top section 49 lying in close heat-conductive contact with the top of the receptacle, and a plurality of

radiallyextending legs

50 and 50.

In order that the legs will extend to `different parts of the body of the exothermic material for the purpose of conducting heat therefrom to the flat top section, the legs 50 extend radially outwardly, while the legs 50' extend radially inwardly from the periphery of the central fiat -top section 49. When the receptacles are closed with the springs in them, the tops of the receptacles exert a pressure on the legs which spreads the legs 50 outwardly and the legs 50 inwardly, as shown in Figs. 6 and 7. When the exothermic material expands and lifts the cover portions 40 of the receptacles 36 and the food container, the legs 50 and 5U', which were under compression, raise the covers 49 and maintain them in tight heat-conductive contact with the bottom of the food container. The legs U and 50 of the spring member conduct heat from the m-ass of the exothermic material to the central flat top section 49 from which it is conducted to the top of the receptacles 36 and by them to the bottom of the food container.

The self-heating containers of this form of the invention will be enclosed in an insulating casing, the same as the container of the'preceding figures; and otherwise are the same and put into operation in the same manner as the container of that embodiment of the invention.

Fig. 8 illustrates a somewhat simplified design of lthe self-heating container. In this embodiment of the invention, the metallic food receptacle 52 has its bottom formed with a dome-like portion 53 which extends into the food container a distance equal approximately to one-half its height. The food container is completely enclosed and hermetically sealed within an outer supplementary container 54. The top of the outer container is removably connected to the body portion thereof by a sealing strip 56 which may be wound onto a suitable key when the cover is to be removed. Such means for hermetic-ally sealing metal containers are well known in the packaging art and are used extensively in the hermetio sealing of packaged coifee.

The side walls of the outer container are provided with an inwardly-extending peripheral groove or circumferentially spaced indentations 51 for engagement by the crimped sealing flange 58 at theperiphery of the bottom of the food container to limit outward movement of the food container.

The space within the dome-like portion 53 and the space between the bottom of the food container 52 and the bottom of the outer container 54 is filled with burnt lime or other exothermic material which will react with water with resultant expansion and liberation of heat.

As in the previously-described embodiments of the invention, the bottom of the outer receptacle is provided with slight indentations 59 to facilitate the punching of holes for the passage of water to the exothermic material when the container is to be put into operation.

The side walls of the outer container 54 extend below the bottom wall of that container to provide a circumferential flange 60 of adequate depth 10 to define a space just suiiicient to receive an amount of water to properly activate the exothermic material.

To facilitate the transfer of heat from the interior parts of the exothermic material, metal shavings such as are shown in Figs. 1 to 3, or metal springs, such as are shown in Fig. 6, may be embedded in the body of exothermic material; or chains or other exible members 6| of good heat-conductive material may be soldered to the bottom of the food container and extend into the body of exothermic material. As the food container 52 is raised under the expansive force of the exothermic material, such flexible members provide a good heat-conductive path from the interior of the body of exothermic material to the bottom of the food container.

The provision of the dome-like portion 53 brings the source of heat into the central portion of the food in the food container and thereby enables the food to be heated more quickly, since the heat does not have to travel as great a distance to the food in the more remote portions of the food container; and also because a greater heating surface is provided for the transfer of heat from the exothermic material to the food within the food container.

In Fig. 9 we have shown a self-heating container which is particularly adapted to the thawing and subsequent heating of frozen foods.

In this embodiment of the invention, the con-v struction of the food container, its outer supplementary container and the receptacles for the exothermic material are the same as the corresponding parts of Figs. 1 to 3 except that the gauge ring 23 is omitted at the bottom of the container and the bottom of the outer supplemental container 3a is dished to provide aspace to receive water to activate the exother-mic material, and outward movement of the food container is limited by an inwardly-extending circumferential groove 6EL in the side wall of the outer container rather than by an inwardly-extending flange portion at the top of the side wall of that container. In this embodiment of the invention, the same reference characters primed are used to designate those parts which correspond to similar parts of the self-heating container shown in Figs. 1 to 3.

Frozen foods are very poor conductors of heat. Therefore, when frozen foods are to be heated, the eiciency of the heating can be greatly increased if the heating is done in two stages and. with separate bodies of the exothermic material; one stage and one body of exothermic material being used to thaw the frozen food, and the second stage and the second body of exothermic material being used to heat the thawed food to the desired temperature. To that end, the selfheating container in this embodiment of the invention includes a supplemental body of the exothermic material 63 contained in a tray or receptacle 64 of aluminum or other good heat-conductive material on top of the food container. The bottom of the receptacle 64 is shaped to accurately conform to the top of the food container I so that it will have a good heat-conductive contact therewith.

A springy body of aluminum or other metal shavings lla, or of any of the other forms of heat-conductive means heretofore described, is embedded in the exothermic material 63 to facilitate the transfer of heat from the inner parts of the exothermic material to the bottom of the receptacle 64 when that body of exothermic material is being used to thaw the frozen food.

amazes A cover 65 fits over the receptacle 64 and hasa depending side wall which extends .to .adjacent the bottom of the outer container .2' .and .is hermetically sealed thereto .by a sealing strip -66 to prevent access of moisture of the air to .the exothermic `material .in the receptacles 8 and 64. The top .of the cover member .65 has slight indentations 61 to facilitate punching to form holes for lthe admission Yof Water to the exothermic material 63 when the heating eifect thereof is to be utilized to thaw the frozen food.

The peripheral edge of the top of the ,cover member 65 is Aprovided with an outwardly-ex tending 'flange 68 which limits outward .movement of .a gauge ring 69, which, like vthe gauge ring23 of Figs. 1 to 3, is provided to denne aspace to receive a supply of water just sumcient to activate the exothermic material 263. Outward movement of the gauge ring '69 is Ylimited by .an inwardly-extending flange 'ILO at 'its inner end engaging the outwardly-extending flange '6B cf the cover 65.

The entire unit above described is enclosed .in a casing 2E'3L of cardboardor other insulating .material. The cover of the casing 2lia normally is secured in place by a sealing strip '3911.

When the self-heating container of 'this embodiment of the invention is to .be put into operation, the sealing strip 36a vis removed .and the self-heating unit removed from the .insulating casing 26K. The sealing strip 66 is then removed. Holes are then punched through .the indentations 61, the gauge ring 69 lifted until the flange 10 at the lower edge thereof engages the ila-nge G8, and the space defined by .the gauge ring .lled with Water. As soon as V.the water has passed through the punched holes into thelime or other exothermic material, the unit is .inverted and put back into the casing with Vthe receptacle G4 for the exothermic material `63 at the bottom and permitted to remain therein until all of the 'heat given off by the exothermic material is absorbed by the frozen food.

As the lime or other exothermic material expands on reaction with the water, the wall ofthe receptacle 64 in contact with the food container will be pushed tightly against the food container in good heat-conductive relation thereto. Also, the expansion of the lime will cause both the food container and the outer supplemental Vcontainer 2 to be raised with the vcover member '65.

After the frozen food has absorbed the `heat from the exothermic material, the unit is again removed from the casing and the cover member 65 and the receptacle .64 both removed and discarded. The exothermic material 4in the receptacls 8' is then activated and the food, now completely thawed, is heatedin the manner previously described in connection with the embodiment of the invention shown in Figs. 1 to 5.

Ordinarily, means will not be provided .to limit the expansion of the exothermic material 63, since the use of such means might interfere with the ready removal of the receptacle '64 after the heat of the exothermic material E3 .has been Autilized to thaw the frozen food.

In order to facilitate the inward .turning of the upper edge portions of the side walls of .the .outer supplemental containers to ,form the .limiting flanges shown in Figs. Yl, .2 and 6, after the flood container has been Iinserted into the outer container, a wire ring H is .dropped into the space between the side walls .of the food container 'and the outer container to rest upon and be supported by the outwardly extending vcrimped seal at the lower peripheral edge of the `food container to A12 act as an anvil about which the umn' -eugefot the outer -containersmay lbe turned during the iianging operation.

While yall .embodiments of the invention -above described `are dry packs, in that none .of the units is provided with water to activate y.the exothermic material, it is to be understood that, if desired, .the several Vforms of the self-.heatingcontainers specically described may be modified to include a water receptaclesuch as is Idisclosed in the fore-said application.

In `the several forms of the inventiondescribed, the Yheat generated by the reaction .of the exothermic material with water .is utilized to .the maximum .extent in heating the food, and -dissipation of heat to :the .surrounding atmosphere is maintained at a minimum. Consequently, less of the exothermic material .is needed to bring the food `toa predetermined temperature, and .the voverall size of the self-heating containers may be smaller lthan otherwise. Also, .the invention .provides .a .self-.heating container in which all of the ex=othem1ic material is between the bottom of .the food container and the bottom of the outer container, and .good heat-conductive paths are provided Vfor Iconducting lthe heat therefrom .to-the flood in thefood container.

Various changes may be made .in .the .details of 'the construction of the various self-heating containers without ,departing from the invention or sacri'cing the advantagesthereof.

We claim:

l. A self-heating container comprisinganouter container. a food container of heat-conductive material within the outer container .and telescopi-cally movable therein, an .exothermic material which on reaction with water liberates heatVJan-d expandsbetween adjacent .ends of Athe food container and the outer container, Vand means for 'limiting telescopic .movement of lthe food container within the outer container when the food .container .is subjected to the force of the expanding exothermic material.

2. A self-heating container as `defined in claim l in which the limiting means includes cooperating engaging vportions carried lby vthe outer oontainer and the food container, respectively.

3. A-self-heating container as defined in claim 2 in which .the amount of exothermic :material between Ithe food container and the outer Vcontainer is such that .the .cooperating ,portions lcarried .by those containers will engage and limit telescopic movement of the food container while the exoithermic material still is ten-ding to-expand when .reacting with water.

4. A self-heating container as defined in .claim 3 in which the .outer container is enclosed .in a telescoping insulating casing.

5. A self-heating container as defined in=claim 3 in which the outer container has one end'open and the cooperating means carried thereby :for limiting telescopic movement of the food container is .positioned |adjacent the open end'thereof.

`6. A self-heating container as Ydefined in claim 5 in which the cooperating Ylimiting means carried by the food container is an outwardly-extending projection adjacent the inner end of 'the food Container.

'7. A self-heating container as dened in claim 5 in which the routwardly-eictending projection of the food container is continuous-and its outer edge lies lclosely adjacent the inner surf-aces of the side walls of the outer container to prevent substantial passage of exothermic materialfwhen the exoth-ermic material is activated by reaction with water.

8. A self-heating container as defined in claim in which the cooperating limiting means carried by the louter container is lan inwardly-extending 'flange at the open end of the sid-e walls thereof.

9. A self-heating container as deiined in claim 5 in which the `cooperating limiting means carried by the outer container is an inwardly-e tending projection adjacent and inwardly from the open end of the side walls thereof.

10. A self-heating container as defined in claim 5 in which means are provided at the open end' of the louter ycontainer for making a hermetic seal with the side walls of the food container.

11. A self -heating container as deiined in claim 1 in which material of good heat-conductive properties extends into the body of the exothermic material and is in good heat-exchange relationship with the adjacent end of the food container.

12. A self-heating containerl icomprising an outer container, a food container of heat-conductive material Within the 'outer Icontainin and telescopically movable therein, a plurality of telescopic receptacles of good heat-conductive material between adjacent ends of the food `container and fthe outer container, said receptacles making a good heat-conductive contact with the adjacent en-d of the `food container, an exothermfic material which on reaction with water liberates Iheat and expands iwithin 'said receptacles, whereby when the exothermic material within the lreceptacles is activated, th-e receptacles Will Iconduct heat from said material to the adjacent end of the food receptacle.

13. A self-heating container as defined in claim 12 which includes means for limiting telescopic movement of the food container within the outer container when the food container is subjected to the force of the expandingexothermic material.

14. A self-heating container as deiined in claim 13 in which the receptacles generally are sector shaped.

15. A self-heating container as defined in claim 13 which has heat-insulating means between the outer edges of the receptacles and the outer container.

16. A self-heating container as deiined in claim 13 which has heat-insulating material between said receptacles and the adjacent end of the outer container.

17. A self-heating container as defined in claim 13 in which a layer of the exothermic material is between said receptacles and the adjacent end of the outer container to heat insulate the receptacles from the outer container.

18. A self-heating container as deiined in claim 13 in which the walls of the receptacles nearest the adjacent end of the outer container have openings therein for the passage of Water to the exotherinic material.

19. A self-heating container as defined in claim 13 in which the walls of the receptacles nearest the adjacent end of the outer receptacle have openings therein for the passage of water to the exothermic material, and in which portions of said walls of the receptacles adjacent the openings are bent inwardly into the exothermic material.

20. A self -heating container as deiined in claim 13 in which the walls of the receptacles in contact with the food receptacle are shaped to accurately conform to the contour of the portion of 1'4 the wall of the food container with which they are in contact.

21. A self-heating container as defined in claim 13 in which the overlapping sides of the telescoping receptacles make a good heat-conductive contact with one another.

22. A self-heating container as defined in claim 13 in which the overlapping side Walls of the telescoping receptacles are of sufficient height to remain in heat-conductive contact with one another when the food container has telescopically moved the maximum amount permitted by said movement-limiting means.

23. A self -heating container as deined in claim 13 in which members of good heat-conductive material are embedded in theiexothermic material and continuously maintain contact with the walls of the receptacles nearest the food container during expansion of the exothermic material and provide a good heat-conductive path from within the mass of the exothermic material to said walls of the receptacles. v

24. A self-heating container as defined in claim 23 in which said members of good heat-conductive material are an expansible mass of flexible material.

25. A self-heating container as defined in claim 23 in which said members of good heat-conductive material are springs.

26. A self-heating container as defined in claim 23 in which said members of good heat-conductive material are spring members having a at central portion in contact with the walls of the receptacles which contact the food container, and radial ngers extending from said iiat centrai portion into the mass of exothermic material.

27. A self-heating container as defined in claim 1 in which flexible members of good heat-conductive material are attached to the wall of the food container adjacent the exothermic material and extend into the exothermic material.

28. A self-heating container as deiined in claim 12 in which the end of the outer receptacle has means for retaining a body of water to activate the exothermic material.

29. A self-heating container as dened in claim 28 in which the water-retaining means comprises a gauge ring telescopically mounted on said end of the outer receptacle and means for limiting the outward movement of said gauge ring.

30. A self-heating container as defined in claim 28 in which the water-retaining means comprises an inwardly-concaved end wall at said end of the outer container.

31. A self -heating container as defined in claim 12 in which means are provided for hermetically sealing the cuter container.

32. A self-heating container as defined in claim 12 in which the outer receptacle comprises a bottom and side walls and a cover that extends over the food container and has side walls overlapping and hermetically sealed to the side walls of the outer receptacle.

33. A selfheating container as defined in claim 12 in which the receptacles generally are sectorshaped and have their radial side walls terminating short of one another at their inner ends to provide an opening into each receptacle at its apex, and a central space communicates with the respective openings at the apices of the receptacles.

34. A self -heating container as defined in claim 1 in which the end of the food container adjacent 15 the `exothermic material has a concave portion extending well into said container toprovide `space `for the exothermic material.

35. A self-heating container .for frozen foods which .comprises an outer container, a food container of heat-conductive material within the outer container and telescopically movable therein, an exothermic material which on reaction with Water liberates heat and expands between one .end of the food container and the corresponding end of the outer container, means for limiting telescopic movement of the food container within the outer container when the .food containeris subjected to the force of said expanding ,materiaL and similar exothermic material between the food container andthe other end of the outercontainer.. Y

`16. A self-heating container as defined in claim 35 in which the exothermic material at said other end is in a receptacle of good heat-conductive material which has a good heat-conductive contact with said other end of the food container, in which the outer container is an open-ended one having a bottom and side walls, and in which a. cover member extends over the food container and the receptacle for the exothermic material at said other end of the food container and has side Walls overlapping the side walls of said openended outer container.

EUGENE J. RIVOCHE. LEV SUKACEV.

i6 REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number vName Date 249,769 Johnston Nov. 22, 1881 794,848 Bohm July `-18, 1905 820,638 Gabriel May 115, 1906 1,751,387 Bielek Mar. 18, 1930 1,955,610 Seipt Apr. 17, 1934 1,971,364 vZimmer etal Aug. 28, 41934 2,185,799 Blake retval Jan. 2, 1940 2,212,441 Katz Aug. 20, 1940 2,327,447 `OBrien Aug. 24, 1943 2,425,900 Steven Aug. 19, 1947 '2,553,878 vSteven May 22, 1951 'FOREIGN APATENTS Number lCountry Date 35,021 Australia Nov. 10, 1908 70,425 Australia Nov; ll), 1915 V2,360 Great Britain Yof 1915 747,004 France Mar. 21,1933