Portable flameless heat pack

Abstract

A user-activatable, flexible heat pack ( 100, 300 ) has two opposed major surfaces. ( 102,104/302,304 ) The heat pack includes a first chamber ( 106,306 ) containing a first reactant and a second chamber ( 108,308 ) containing a second reactant. The first and second reactants are adapted to react exothermically with one another when mixed. The first ( 106,306 ) and second ( 108,308 ) chambers are separated by a frangible seal ( 112,312 ). A third chamber ( 110,310 ) contains solid-to-liquid phase change material that is substantially across one of the opposed major surfaces.

1 . A user-activatable, flexible heat pack having two opposed major surfaces, the heat pack comprising:
 a first chamber containing a first reactant;   a second chamber containing a second reactant, wherein the first and second reactants are adapted to react exothermically with one another;   a third chamber containing a solid-to-liquid phase change material,   wherein said first and second chambers are separated by a manually frangible seal and wherein the phase-change material is located substantially along one of the opposed major surfaces.   
     
     
         2 . The heat pack according to  claim 1 , wherein the phase-change material comprises a flexible wax sheet. 
     
     
         3 . The heat pack according to  claim 1 , wherein the phase-change material comprises discrete solid units at fixed locations across the one of the opposed major surfaces. 
     
     
         4 . The heat pack according to  claim 1 , wherein said first heat-producing reactant is sodium permanganate and said second heat-producing reactant is glycerol. 
     
     
         5 . The heat pack according to  claim 1  further comprising a non-reactive liquid heat sink in at least one of said first and second chambers. 
     
     
         6 . A method of heating a surface of an object comprising:
 activating a heat pack according to  claim 1 ;   applying the heat pack to said surface; and   reversibly mechanically conforming the heat pack to the surface.   
     
     
         7 . A user-activatable heat pack comprising:
 a first chamber containing a first reactant;   a second chamber containing a second reactant;   a frangible seal between the first and second chambers, wherein rupturing the frangible seal permits mixing of the first and second reactants to initiate an exothermic reaction; and   a third chamber containing a phase-change material,   wherein the phase-change material is adapted to at least partially change phase by absorbing at least some of the heat generated by the exothermic reaction, and   wherein the phase-change material is adapted to at least partially return to its original phase by releasing at least some heat to its surroundings.   
     
     
         8 . The user-activatable heat pack of  claim 7  wherein the phase-change material is adapted to change between a solid phase and a liquid phase during the exothermic chemical reaction. 
     
     
         9 . The user-activatable heat pack of  claim 7  further comprising two opposed major surfaces, wherein the phase-change material is formed as a sheet that extends substantially across one of the two opposed major surfaces. 
     
     
         10 . The user-activatable heat pack of  claim 7  wherein the phase-change material comprises wax. 
     
     
         11 . The user-activatable heat pack of  claim 7  wherein the third chamber is substantially vacuum sealed. 
     
     
         12 . The user-activatable heat pack of  claim 7  wherein the third chamber is subdivided into a plurality of compartments, each compartment containing a discrete unit of the phase-change material. 
     
     
         13 . The user-activatable heat pack of  claim 7  wherein the phase-change material's melting temperature is lower than a desired maximum operating temperature of the heat pack. 
     
     
         14 . The user-activatable heat pack of  claim 7  further comprising a non-reactive liquid heat sink in at least one of said first and second chambers. 
     
     
         15 . The user-activatable heat pack of  claim 7  wherein the first reactant is permanganate and wherein the second reactant is glycerol. 
     
     
         16 . A method of heating a surface, the method comprising:
 providing a user-activatable heat pack according to  claim 7 ;   rupturing the frangible seal to initiate an exothermic chemical reaction in the heat pack; and   placing the heat pack in contact with the surface to be heated.   
     
     
         17 . The method of  claim 16  wherein the heat pack comprises at least one major surface and the phase-change material is a sheet that is proximate the at least one major surface, wherein placing the heat pack in contact with the surface to be heated comprises:
 placing the at least one major surface that the phase-change material is proximate against the surface to be heated.   
     
     
         18 . The method of  claim 16  wherein the heat pack comprises two opposing major surfaces and the phase-change material is a sheet that is proximate one of the two opposing major surfaces, wherein placing the heat pack in contact with the surface to be heated comprises:
 placing the major surface that is not proximate the phase-change material against the object.   
     
     
         19 . The method of  claim 16  further comprising reversibly mechanically conforming the heat pack to the surface to be heated. 
     
     
         20 . A user-activatable heat pack having two opposed major surfaces, the heat pack comprising:
 a first chamber containing permanganate;   a second chamber containing glycerol;   a frangible seal between the first and second chambers, wherein rupturing the frangible seal permits mixing of the permanganate and glycerol to initiate an exothermic reaction; and   a third chamber containing a phase-change wax material; and   a non-reactive liquid heat sink in at least one of said first and second chambers;   wherein the phase-change wax material is adapted to at least partially change phase by absorbing at least some of the heat generated by the exothermic reaction,   wherein the phase-change wax material is adapted to at least partially return to its original phase by releasing at least some heat to its surroundings, and   wherein the phase-change wax material's melting temperature is lower than a desired maximum operating temperature of the heat pack.