Warming device for generating heat by controlled exothermic oxidation of iron powder

Claim 1

A heating device for generating heat by an oxidizing reaction caused by contacting iron powder, metal salts of acids, with water and air, to gradually oxidize the iron powder, said device comprising: an inner pouch having an air and water permeable wall; a quantity of initially dry iron powder and metal salts of acids within said inner pouch; means closing said pouch to prevent the escape of the iron filings and metal salts of acids from the pouch; an outer covering of waterproof material for containing the inner pouch; means for opening and closing an opening in said outer covering to permit insertion into, and removal of said inner pouch from the outer covering; an initially dry water absorbing element within said outer covering and engaging said wall of the inner pouch said water absorbing element being selected from the group consisting of, a sponge, synthetic resin-foamed material, or cellulose; said outer covering having a plurality of thermoregulating holes formed therein on only one side thereof and said water absorbing element facing toward another side of the outer covering which is free of holes; said air and water permeable wall of said inner pouch cooperating with said water absorbing element and the holes in the outer covering to provide means for moistening the iron filings and salts and for allowing the circulation of air, to provide a controlled exothermic reaction, after supplying the water absorbing element with a predetermined quantity of water; said water absorbing element moistening said iron powder and salts through the water permeable wall, without excessively wetting said iron powder and salt, so that vapor generated by heat in the pouch can permeate the wall of the pouch together with air to control the generated heat; and wherein said water absorbing member comprises means for allowing the user, when heat is to be generated, to add to the device a predetermined quantity of water less than that required for complete oxidation of the iron powder, by wetting the moisture absorbing element, so that the device can be reused by later adding more water to the water absorbing element.