US2520972A - Heat insulating cover - Google Patents

Description

Sept. 5, 1950 P. A. slPLE HEAT INSULATING COVER 4 Sheets-Sheet 1 FileMay 22, 1945 Sept. 5, 1950 Filed May 22, 1945 IP. A. SIPLE HEAT INSULATING COVER 4 Sheets-Sheet 2 INI/EN TOR.

ffm ww 4 Sheets-Sheet, .E

P. A. SIPLE HEAT INSULTING COVER Sept. 5, 1950 Filed Mayfzzn 1945 INVENTOR /w mww Septo 5, 195@ P. A. SIPLE 2,520,972

HEAT INSULATING COVER Filed May 22, 1945 4 SlLxeelzs-SheeI 4 -l N V EN TOR.

l "i: "66 M@ g Patented Sept. 5, 1950 UNITED STATES PATENT OFFICE HEAT INSULATING COVER Paul A. Siple, United States Army, Arlington, Va.

Application May 22, 1945, Serial No. 595,229

(Granted .under the act of March 3, 1883, as

Claims.

The invention described herein, if patented may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

My invention relates to protective covers and more particularly to a cover for enclosing nonanimate bodies of various sizes and shapes to protect them from flames and intense heat so constructed that it may be permanently or removably secured about the body and including means sealed within its walls for dissipating the heat therefrom under conditions of abnormal temperature.

In the past various means have been devised for protecting safes, file cabinets, mail pouches and other receptacles for containing or storing valuables oi all kinds against heat and flames. In all of these covers the protection aorded is secured by thermally insulating the inner storage space from exterior heat, and various constructions have been devised for this purpose. The Walls of the protective covers may be made from material of low heat conductivity, or a thermal insulating material may be disposed intermediate the inner and outer Walls of the protective container, or a dead air space or spaces may be provided in these walls or various combinations of these constructions may be used. Such covers and containers are effective only to the extent that these specially constructed walls prevent conduction of heat inwardly, and in this respect they are often inadequate. Although ames may be prevented from reaching the interior compartments, nevertheless, so much heat is conducted through the walls that the objects or materials stored therein are scorched or damaged in other respects by the heat. The only means of preventing this is by increasing the thickness of the walls of the containers, but consideration of factors such as the space available or limits on permissible loads may limit the thickness oi' the walls. For example, pouches for carrying registered mail, air mail or valuable cargoes by train, ship or air express must not only be sturdy and compact but also light in Weight so that the largest possible pay load can be carried on each trip. There is a practical limit to the permissible wall thickness in such containers or pouches which, if exceeded, destroys the usefulness of the container. The protective covers described and claimed in this application are particularly suitable, but not limited to use in such applications. As the description proceeds, it will be obvious that they are equally adaptable and effective for use in protecting stationary storage receptacles such as le amended April 30, 1928; 37.0 O. G. 757) cabinets, safes and storage boxes of all kinds. By making use of my invention it is possible to construct a heat insulating protective cover with relatively thin walls because I provide a vaporizable coolant sealed in the walls of the cover or container and releasable after a predetermined temperature is reached, for absorbing heat from the walls of the cover and dissipating it to the surroundings to prevent its transfer inwardly t0 the interior of the container. Thus, it is possible to provide ample protection with a relatively thin walled cover. It has been found that covers constructed in accordance with my invention are particularly suitable for use in protecting valuable cargoes carried by airplanes because in the event the plane crashes and burns the re, ordinarily, is of relatively short duration, but the heat generated is very intense. Sufcient coolant can be carried within the Walls of my protective cover to prevent the transfer of heat therethrough for the duration of the fire. It is, therefore, an object of my invention to provide a new and improved heat insulating cover in which a coolant is provided in the walls of the cover for absorbing heat conducted into the walls and dissipating it to the surroundings after a predetermined temperature is exceeded.

Another object of the invention is the provision of a new and improved protective cover for normally stationary cabinets, safes and other receptacles for valuables which may be constructed in sections and dismountably secured about the receptacle to be protected to provide all around protection therefor.

Another object of the invention is the provision of the new and improved heat insulating cover which has a readily vaporizable substance having a high heat of vaporization non-escapably sealed Within its Walls at normal temperatures, but which is vaporized by abnormal external heat and as a vapor discharges outwardly from the walls carrying with it the absorbed heat of vaporization which is thereupon dissipated to the surroundings.

Another object of the invention is the provision of a new and improved heat insulating cover having laminated walls, including laminations which non-escapably retain a coolant therein at normal temperatures, but which upon heating of the walls above a predetermined temperature permits the escape of the coolant in vaporized form.

Another object of the invention is therprovision of a new and improved heat insulating cover having outer wear resistant walls and having inner Walls for non-escapably retaining a coolant Y section, ofthe cover .show-n atoae'm between the outer walls at normal temperatures, the exteriorly facing walls being weakened by abnormal external heat so that rupturing of these walls by the Vaporized coolant is promoted and the vapor discharges through the outer walls thereby dissipating the absorbed heat of vaporization.

Another object of the invention is the provision of a new and improved heat insulating cover which is light in weight, durable and compact in construction, inexpensive to manufacture and which may be used in covering objects'of various sizes and shapes. v l v These and other objects of the invention will become apparent from the following idescription and accompanying drawings in which, Figure Al is a front elevational view of my improved cover secured on a iile cabinet the front :panel removed to more clearly` illustrate the Aconstruction and the manner in which my cover is mounted.

2 a side elevational View of the pro- .teetive covershovmzin Figure 1 with a side 'panel removed.

Figure is :a top plan lviewrpartly in section, of the protective cover shown in Figure 1 with the .topfpanell removed Fig-.ure 4 a fragmentary :sectional View taken 'on the 'line tt :of .Figur-e 5' is fa tragrrentarysectional View ftaken on the 1li=ne5-5lof Figure i3.

'Figure l6 is la :side elevational View partly Yin section Aslfrowin'g anexrble 2'heat insulating-cover constructed in accordance withmy invention.

.Figure E7 is a partial top plan view'partly--in 1 Figureb'.

Figure i8 is a fragmentarysectional view show# ing'the manner 4in which the Walls lof the cover shownin Figure dare constructed.

Figure 9 isa verticalfsectional' view :showin-g a serniexiblle vvcontainer constructed accordwith my invention.

Eiglure lfd is aperspective ew showingfafskel'eton [for snpporizing the walls of "the .protective cover :shown in .Figure Q.. Y

Figurel'l is a horizontal'cross'sectional view taken on the line H-II of Figure 9.

Referring to the drawings, in which similar characters oi' reference indicate similar .pants throughout theseveral lviews, -Inav'e .shownV by stay-nf 'illustration in ylili-.figures l "to 5.a heatinsulating Acover for :a rile y.cabinetinnerdorati-ng'the princtple of niyiirzvention. `@he cabinet "Ms of standard construction'and isfsurroundedvby panels i2 which when assembled toria or ures .4 and :5. A plurality 'of thermal insulating.

pads I1 are secured in the space between panel Walis |.3-'a'nd 14, four Apads of similar construction .being shown in the side andend -ipanel-s. Each of these-pads consist of an inneriayer of absorbent material 18 completely *enclosed lor jacketed by 'a layer ofliduid and vapor inlpermeablezmaterial t9. The :absorbent-layer *t8 ,is

4 are of such size that when placed in juxtaposed relation in the panel they completely overlie the inner wall thereof. Any material having high water absorbent properties such as Fiberglas cloth or wool may be used for the absorbent layer I8, and the impermeable jacket is made from a material impermeable to both vliquid and vapor at normal temperatures, Aas rubber or vinylite latex or any of the synthetic rubbers or plastics which are impermeable to both liquid and Vapor. The .pads in this form of the invention are not Te'qlnred to'be flexible so the impermeable jacket I9 maybe constructed from a rigid material if desired.

The bolts cr rivets l5 are so spaced in the walls :of the panel that they pass between adjacent pads l'! as shown in Figures 4 and 5, and thepads l'are held place by a plurality of metal straps 21B extending from top to bottom of the panel. These straps have apertures through which-the bolts i5 and .sleeves iS pass, and Ithey are held 'in .snug engagement with the router face oi rtl-ie 'pads by means of spacing sleeves or blocks 2l secured ron the bolts .l 5 .over the spacing sleeves l5. These blocks 21 bear against inner side .oi theouter wall 'til of the panel and the loutersuriac'e of the-strap 2l@ as -rnost clearly in 1l' and 5.

I-f desired ya lpad or layer of thermal insulating material 122 may be placed between `the pads 'll the inner wall i3 'of the panel l2 to prevent the transfer v'of heat from the pad yI' to the inner wall of the panel or to the walls Aof the cabi-riet, but `this insulating layer lis not allisolutely essential `in all lcases because the tempera-ture of thenner A'side .ofthe pads i? will rarely exceed the boiling point Aof water, and, except in unusual cases, this deg-ree of temperature will not damage 'thelcontents @faille cabinet.

iA-plurality of vents 123 are provided in the outer walls -Il or" each 'of the panels I2 to ypermit the escape-ef "vapor from the interior of `the panels. A 'veiitically extending flange 2'4 is formed on each of the vertically extending edges 'of the outer walls :lf3 o'f the side panels of the cover by folding these edges inwardly through an angle` oi 'These flanges are secured to fthe outer edges of the outer wall-s M oi the front and rear panels which' extend beyond the ledges -of- `tl 1e inner walls oi these panels to engagethese -ilanges on'the iside panels. A plurality of bolts' 25 vare permanently secured v'in the Vflanges and engage in apertures adjacent the edges of .the outerwall of the front and rear `panels of the covering asshown in Ylil-igures-'Zand-ii. Wing nuts-'are threaded on-'the outer ends of these bolts and, when tightened, secure the front and back panels to the side panels to 'form a housing 'having an open top and bottom. I

The top and bottoni 'panels of the cover-ing are of 'similar l'construction 'to the side 'panels'but the outer edges of the outer walls- I4 of "these panels are folded downwardly to form sides `anden'dsf'l for 'these panels, 'and the free edges of these sides and -ends are Aoil-set Iinward-ly as indicated at in Figures 4v and so 'that these edges of the top-and bottoni panels are receivable in the open top vand bottom of 'the y'covering and snug-ly engage the edges of the outer walls M of the front, 'and side panels l2. 'If desired 'the oft-set vedges ofthe top and bottom panels and the adjacent edges of the vertically extend-ing panels may be rapertured for the reception of bolts for permanently securing the atop 'antibot-torn panels to the vertically extending iront, rear and side panels.

andere'.

` It will be apparent from this description that the panel construction which I have described is subjected to abnormal heat the water in thev pads I1 is vaporized and as the pressure in the pads increases the vapor ruptures the impermeable walls I9 of the pad and escapes to the space in the interior of the panel and from this space to the exterior through the vents 23 in the walls I4 of the panels. Escaping vapor carries with it the latent heat of vaporization absorbed by it in being vaporized and dissipates it to the surroundings. In this manner heat is carried from the walls of the cover and is prevented from being conducted inwardly through those walls, and, as a result, the interior compartment of the cover is maintained at a relatively low temperature.

If the walls of the pads I1 are constructed from a rigid material they are provided with vents which have Stoppers adopted to be blown out by the vapor in the pad when its pressure exceeds a predetermined amount. Vents of this type may also be used if desired when the pads are provided with exible impermeable walls, but rupn turing of the impermeable Walls will be facilitated by the action of heat because the heat tends to cause deterioration of these walls so that they are more easily ruptured. The absorbent layers I8 holdthe liquid water after the impermeable walls are ruptured so that it does not leak from the pad.

For certain types of depositories for valuables such as safes or even in iile cabinets a thermal insulating means constructed as above described may be built into the walls of the depository or cabinet. If this type of construction is applied to a safe the thermal insulating pads Il are posiu tioned in the walls of the safe under the outer armor plating of all of the walls including the door, and vents 23 are provided in those walls to permit escape oi vapor. When the thermal insulating pads are built into a file cabinet an outer metallic shell is provided and the pads are secured in the space between the cabinet wall and the shell. A layer of thermal insulating material, similar to the layer 22, is preferably positioned between the Walls of the cabinet and the pads and the drawers are provided with double front walls within which is inserted a heat insulating pad and a thermal insulating layer.

In Figures 6 to 8, I have illustrated a form of my protective cover which has flexible walls and may be used to contain objects of various sizes and shapes or may be used for transporting valuables such as registered mail. This cover conu sists of two bags placed one over the other as illustrated in the drawings, but in many instances a singlev bag of this type will be sufcient. The double bag construction in addition to providing greater protection over the sides has the advantage of providing a 4permanently closed end of the bag over each end of the object.

In this form, the invention consists essentially of a plurality of sleeves having one end closed arranged one over the other in predetermined orderI to form an inner bag 28 and an outer bag 29. In Figure 8 I have shown a cross section thou'ghthe walls 'of these bags on a slightly en-llarged scale. Each of the bags comprising thisdouble ncover includes an inner layer or sleeve 39 of any suitable water absorbent material similarl to the absorbent material |8 used in the padsI I"| of the modification first described. This sleeve is completely overlaid and underlaid by a layer' of liquid and vapor impermeable materialwhich forms 'an inner sleeve 3| and an outer sleeve 32 adapted to seal therein at normal temperatures the liquid coolant contained in the absorbent. layer. A flexible material, similar to that previously described forV use in the impermeablejacket I9, may be used in making these impermeablel sleeves. The outer impermeable sleeve 32 of the inner bag 28 and both of the impermeablesleeves in the outer bag 29 are of reduced thickness with respect to the inner sleeve 3| of the rinner bag 28 so that under conditions of ex ternal heat and internal pressure on these sleeves the thinner sleeves will rupture whereas the thicker inner sleeve 3| of the inner bag 28 remains whole and prevents vapor or liquid from reaching the space within the covering.

= TheV inner bag 2B is provided with a sleeve .33 of thermal insulating material underlying the impermeable sleeve 3|. This sleeve prevents the transfer of heat from the absorbent layer 30 of the inner bag 28 in cases where the heat is so intense or the period of exposure so long that the exterior heat penetrates the absorbent layer` 30 of the inner bag 28.

The outer and inner surfaces of each bag are formed by sleeves 34 constructed from any durable wear resistant textile fabric. These sleeves protect the other layers of the bag from ordinary wear and from accidental damage by sharp objects.

In using this type of cover the objects to be protected are inserted in the inner bag and the open end: thereof is drawn together and held in closed position by binding with a wire 44 or other noncombustible ycord as shown in Figure 6. The inner bag is then inserted in the outer bag, openu able end first, so that this end is overlaid by the permanently closed'end of the outer bag and the open end of the outer bag is closed and secured in a manner similar to the inner bag. When this cover is subjected to abnormal temperatures the water in the absorbent layer 30 of the outer bag 29 begins to vaporize and at the same time the impermeable sleevesv 3| and 32 of bag 29 are weakened by the heat. As the vapor pressure increases these limpermeable sleeves are ruptured,

'and' the vapor escapes outwardly through the outerwear resistant vfabric sleeve 34. If the heat is so intense or the period ofl exposure so long that the absorbent layer 30 of the inner bag 28 becomes heated to the point where the vapor pressure increases suiiiciently to rupture the outer impermeable layer 32 of this bag, then the vapor formed will pass outwardly through the outer bag and to the exterior and the heat carried by it is dissipated to the exterior. In this manner the interior of the covering is maintained in a cool condition.

v The outer wear resistant fabric sleeve 34 and the outer impermeable sleeve 32 of the outer bag 29 will very likely burn off if the heat is intense, but this promotes rather than hinders the cool-l ing action because it allows the vapor to escape more easily. The protected body will remain contained in the inner bag 28, fully protected by it,

even though the entire outer bag burns off, but

this: isrnetflilrelic tmoccuninetherresnordinailyr experienced. f

It willzbesobviousfthaa in sonrie-asituations.ssuf1 cientgzprotection rwillfbezaorded .whema singlet: loagsismsedrandithat other;closure?trienios;y may, berv provided for: sealinge thee openr endsf of thee bagn In; Figures e9; toi 11;. inclusi-vm. Ir havef shown azi insulating cover.: ofi senneflexibler.;construct tion.. Inzthis forrmof; tnefinyenton@ provide-21o;- afa-.skeleton 35iformed.;irormmetallibarsi,orrrodss 36;'which1are secured together. torform thelouts linesaofra-frectangular. shapedetramk and aicnver; 38if'receivabler overrthe trays.. Vilallsgofrlamirrated construction .are isecurednto the.l barsnto-.iornnthe-s s sidesiandrtonandvbottom of thetcompletedcoyerr These; Wallscinclude; an: absorbent layenI 39; urated with-1 water anda impermeables; layers-x 405' which,- extend. over.l all; the.; surfacesl of itherainr sorbent .layers1392 and-r alongr: the f edgesf thereof-i j so'thatohewatergabsorbedin thefabsorbentflavors; isenon-escapablyn seaiedr. therein.: at normaliteme peratures:- The absorbent-layerfandethe;impenmeable layersrrnay be; formedrfrom.anygofitha materials. previously?` nfrentionedr;V in connection with thesimlar layersfini therotheriformsaofrtlie itu/en tion:` TheV :impermeable7 layers arerpreferarfk bly made y'of 1ess1thickness: ori;the:outward-ly;timev r ing surfacesytha-ng onA tlqieffin,wardlygY facing-sur:v faces or.; offa; materialfmorefeasil-y rru'pturedaby.1 3.0;;

Y heat sof.thatzthe.seisides willzrupturesmore;easily.;

than the inwardly facing sides when: they'are'. subj ectedfto; internallpressurefibyj the-evaporizing coolant;4

Tf1-@protectthesewlaversffrom:Ordinary -wear orf 35,; from;aocdentaldamagefa .wea-r. resistantlayer 414; offtextile -fabric isfprovidedzcompletelyl jacket-me; the impermeable layer 40. In assembled relation;` a..coyerconSruG1?d;as abnileedescribedf, comprises altrayli;I and a.,cover. 43 Vreceivableioveiatheetravg 40jassshown irr. Figure Qfanclnsnusly; engaeinerthee sidesfof/:the tray.; It; should begobyous; frmnzfthe1;A descriptionf givenfd thatl the container; just: def scribed mayrbefmade in anysize or-,shapedesiredi and thatwhen vnecessary,t additional ,rods may used at-intermediateippintsinthefskeletontdg. gljaterrigiditytofthe framework.

This `form ofacoverismaintainedin'alcool-,cone lditionlinna2 .manner similar :to that :described with@ than other` formsfof.. the inventiona, The. ati-.wmy sorbedV liquid` in the layers ,V39 is vvaporized ex:- terior-heat and-as other pressure increases :andathe Walls,sbecomewweakened byetheheatfthefyapore ruptures :ther outer WallsAO andescanes. In., .es-..- caping to.the surroundings, it,.,-dissipates..to the, 5.5E exteriorthe latent ,heatnof vaporizationabsorbed. by it in vaporizing andathereby maintainsrtheinal terionoftheycover in afcool .conditionr Whenr coversof any of [the insulatings typs..0 mentioned above are to be used.. where the tern: 6111sk perature drops lbelow the .freezing lpoint. o ffwater 1' it may beadvsable toinclude an' antiefr'eeze in. the water to prevent its "freezing:n Various-other". modifica-tions lmay -be'made irrthe -invention to" provide al -heat insulating cover foreparticulare 65,52 obj eetsf-for `for-use irrfspecial-'locations-orwforespeem cial purposes. For example, the traymandi'covenf shown-inv Figures.A 9 '5tol inmay. bef/provided fwith rigid outer wallsdnateadfioe the l-textile;fabric;:Wallaz el fas-:abone-rdescribedr omtherthermal -ainsnlationr ofgfthe f1astatwoomodiicationsfdesoribed':may bee obtained-.bv .fusingesepanate padsasain theerstfi modincation. .Theavarious,speeic{structures-deffT scribed :hereinl .are f illustrative only and larefnota intended :torestrict theeinventionrto .-.anypo tliefflIY 851 narticolarel forms described except: as limitediby thefclaims included herein:

What I claim as new; and .i desire: :to tsecureby.l Letters Patent .fis-asY follows 1.A l A flexible two:piece.heat finsulatingacover: for: protecting,bodies.nffvariousfsizeszand;shap es;froml external heatcom-prising inner-:andaouter meme:i bersadapt-ed .Lto ber-received `one within .the ^other,-. saidfmembers:comprisingfspaced-feinnerrandiouter-f' sleeves-1,.: absorbent material contained inthespam-ril between said inner-and.outerwsleevesa; coolant-L absorbed: inw-said absorbent'material; said coolant havin-g awhighv heat of vapori'zation anda beina; adaptedfto; bevaporizecl wherr abnormalieXterna-l; heatiscconducted iintosaid*` space vinner:anctouter.` liquid.- and vaporrimpermeable sleeves finesaid ine't ner-z. and; outer members-:for noneescapably 'seal-H ingrsaid coolant in said :membersiatfnormal atom-e peratures;v said'. impermeable!sleevesg-ini.saidfouterr member. andsaid Iouter impermeabletsleeve-inisaidi innerfmember beings. of Weakenedc construction., with respect tofthef-inner impermeable sleevezof' saidinner fmember tov `facilitate;rupturing?theres.- of-runder vconditions- .of eXternal--heatandi internal; pressure, said` vaporized'i coolant?` rupturingsaids weakened 1 sleeves and: f' escaping'v to the'.Y exterion'. said 'escaping vapordis'sipatingstov the-.exterior the absorbed-heat o1vaporization therebyfmainta -f ing the interior 'of-:saidi cover `inta* ;coo1:con'ditin,; saidwmembers :each havingv a permanentlyclosedi end'andran open end adaptedftobe closed:to'.'frmzY av .bagf completely'v enclosing :the bodyftorbefproe tected; said; permanentlyl closed; ends:v of said." members;l being; oppositelyF disposed; whent saidi members are-placedonsaidfbody toxprovide a; permanently .closedsurface over 'each' endsof saido body.:

2: .Af heat insulating; protectivef cover comprise Y ingrfexible-:laminated innerrfan'dfouter vwallsIdirsi-f loosedgto'Y form a `confined4 'space-.thereb'etvveen, absorbent -materiakcontained in saidgvspace; aricoole.; ant:e absorbed; in said; absorbent In'aterfiaL'. sai'dif coolant havingf'iahigh heat'rofv vaporiz'ation; andbeing :l adapted' to. be: vaporized.- when abnormal 2 la external heat isf.. conducted: throne-lr.: said outer;y

Wall, said ,outeitwallgbeingy adaptedzto permit'. 'diss l charge iof'vapor I therethrough," said'. vapor dissie pating the:- absorbed Aheat .of-:vaporizatiomito :thee surroundings whenescaping thereby maintaiming;` the interiorj of said Lcover in. aV coolv condition;` .as liquid` andivapor. impermeable lamination in said :s inner v and outergwalls for.. noneescapa-bly -sealinggj saidzcoolanttintisaid confined space 'at.normalf temperatures, said lamina in saidv outer:wal 1beeing;v of weakened construction r with Y respect; to said-lamina inY saidinnerfwall :to: -faciiitate .-'rupy turingfthereof underzcondtionsfof. external heat; and internal. .vapor pressure, said':cover;having.. a'f permanentlyfclosedend and 'aneopen endi-adanted toiv` be; closed upon-.thee contents: :.A provider all f aroundprotectiontherefor;

gaAitwoepiececheat insulating: covers/compris:

ing-etw@ intertting laminatedzmembers f ofi fiexe iblewmaterial, each of said. members; having; az; permanentlyfclosedifend :and an -opening..facing inlthe direction of the closedlend:ofrthefotherf member, .and leach'n of saidzimernbersf comprising. spaced inner androuter.flexible sleeves; ayflexiblel absorbent .material 'containedin vthe-space within said inner and outer-sleeves, saidiabsorbenty materialrbeingrgadapted to :holdria liquid coolant having arshigl'rrheatio '..vaporization andzvaporize ablefmhemebnormal Xternal heat issconnzluctede` inter. thenspaee rbetweennsaidfsleeves; liquidi: ande vaponeimpermeableiflexbleldaminations-iintermes diate said absorbent material and said sleeves for non-escapably sealing said coolant in said absorbent material at normal temperatures, at least one of said laminations being rupturable under conditions of external heat and internal vapor pressure whereby vaporized coolant may rupture said laminations and may escape to the exterior, said escaping vapor dissipating the absorbed vheat of vaporization to the exterior, thereby maintaining the interior of said cover in a cool condition.

4. A two-piece heat insulating cover according to claim 3, wherein the outer laminations are of lesser thickness than the inner of said laminations, whereby rupturing of said outer laminations under conditions of abnormal heat is facilitated.

5. A heat insulating protective cover comprising flexible inner and outer walls disposed to form a confined Space therebetween, a iiexible absorbent material contained in the space within Said inner and outer walls, said absorbent material being adapted to hold a liquid coolant having a high heat of vaporization and vaporizable when abnormal external heat is conducted into the space between said walls, said outer wall being adapted to permit discharge of vapor therethrough, said vapor dissipating the absorbed heat of vaporization to the surroundings when escaping thereby maintaining the interior of said cover in a cool condition, and liquidand vapor-impermeable flexible laminations intermediate said absorbent material and said Walls for non-escapably sealing said coolant in said absorbent material at normal temperatures, at least one of said laminations being rupturable under conditions of external heat and internal Vapor pressure, said cover having a permanently closed end and an open end adapted to be closed upon the contents to provide all around protection therefor.

PAUL A. SIPLE.

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

UNITED STATES PATENTS

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