Abstract:
A trigger to activate a supercooled aqueous salt solution wherein the solution is encased in a flexible container to form a heat pack, the trigger made of dry or partially dry particles adhering to a support so that when the trigger is manipulated, allowing the dry or partially dry particles to be released and contact the supercooled salt solution, crystallization is initiated and heat is released.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority of Provisional Patent Application Ser. No. 60/276,295, entitled “TRIGGER TO ACTIVATE SUPERCOOLED AQUEOUS SALT SOLUTION FOR USE IN A HEAT PACK” filed Mar. 16, 2001, continued preservation of which is requested. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a trigger to activate a supercooled aqueous salt solution wherein the solution is encased in a flexible container to form a heat pack. The trigger is made of dry or partially dry particles adhering to a support. When the trigger is manipulated, allowing the dry or partially dry particles to be released and contact the supercooled salt solution, crystallization is initiated and heat is released. 
     BACKGROUND OF THE INVENTION 
     Heat packs utilizing supercooled aqueous salt solution have been used for the treatment of soreness of muscles of athletes and sportsmen. Heat packs are also used as infant heel warmers in medical facilities as an aid in drawing blood. Such supercooled solutions include aqueous solutions of sodium acetate and calcium nitrate tetrahydrate. 
     Various techniques of initiating crystallization have been proposed, including inserting a crystal of material into the supercooled solution, injecting air by means of a valve, scraping metal into the container, and squeezing a plurality of rigid objects. Examples of these techniques and others are disclosed in U.S. Pat. Nos. 1,915,523, 1,433,010, 2,289,425, 2,220,777, 3,093,308, 4,077,390, 4,572,158, 5,275,156 and 5,305,733. 
     The present invention provides a trigger made from a support material to which adhere dry or partially dry particles. Such a trigger is typically made from sand paper which is easily manufactured and used. The trigger is used by manipulating to cause the dry or partially dry particles to be released into the salt solution. Preferably, the trigger can be activated using one hand. None of the above references disclose the claimed invention. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a trigger to initiate crystallization of a supercooled aqueous salt solution wherein the trigger is made of dry or partially dry particles adhering to a support. A preferred trigger is made from sandpaper. When the trigger is immersed in the salt solution and manipulated to release dry or partially dry particles, crystallization is initiated and heat is released. The present invention further relates to a heat pack comprising a supercooled aqueous salt solution and a trigger encased in a flexible container, wherein the trigger is made from a support material to which adhere dry or partially dry particles. When the trigger is manipulated, dry or partially dry particles are released, thereby initiating crystallization. Optionally, the trigger is sandpaper is in the form of a disc and is coated with a water-resistant resin 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above advantages may be more clearly understood from the following detailed description and by reference to the drawings. 
         FIG. 1  is a side, sectional view of the heat pack and trigger, wherein the trigger is not activated. 
         FIG. 2A  is a side view of the trigger, not activated, with an optional coating. 
         FIG. 2B  is a side view of the trigger, not activated, uncoated. 
         FIG. 3  is a side view of the heat pack with the trigger being manipulated to activate. 
         FIG. 4  is a side view of the heat pack fastened to an ankle. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 ,  2  and  3 , a heat pack  100  having a trigger  200  made of a support material to which dry or partially dry particles adhere  10 , optionally coated with a water resistant resin  20  has a flexible container  30  which contains a supercooled salt solution  40  which, when activated, releases heat. Suitable solutions include supercooled sodium acetate, lead acetate, calcium nitrate tetrahydrate, sodium pyrophosphate and sodium thiosulfate solutions. The preferred solution is sodium acetate, which is generally harmless to humans. 
     The salt solution  40  is made by dissolving the salt in the desired amount of water. The amount of salt to be utilized should permit the salt solution to be supercooled to at least the ambient temperature at which the heat pack is intended to be utilized. Said solutions are disclosed in U.S. Pat. No. 5,305,733, which is hereby incorporated by reference. 
     Flexible container  30  of heat pack  100  can be made from any water-tight flexible material not adversely affected by the supercooled solution. Preferably, the flexible material is able to withstand the temperatures (generally on the order of about 60° to 65° C.) to which the heat pack  100  can be heated to re-dissolve the precipitated salt in order to reuse the pack. Suitable flexible materials include plastics such as rubber, vinyl, vinyl-coated fabric, nylon polylaminate and polyethylene. Preferably, the flexible container is made from nylon polylaminate of a thickness in the range of about 1 mil (0.026 mm) to 10 mils (0.26 mm). 
     A trigger  200  is made of support material to which adheres dry or partially dry particles  10  optionally coated with a water resistant coating  20 , as shown in FIG.  2 A. The support material can have particles on one side or both. Preferably, the trigger is made from sandpaper  10  which has a rough side  11  and a smooth side  12 . The roughness of the sandpaper can be the result of sand, or other abrasive materials such as aluminum oxide, adhering to the paper. A preferred trigger is emery cloth, which has aluminum oxide particles cemented to a fabric. When the rough side of the sandpaper trigger is manipulated by flexing, rubbing or kneading, aggregate particles break off, causing a dry or partially dry side of the aggregate to contact the supercooled solution. The dry or partially dry particles activate the heatpack, causing crystallization and subsequent heat release. 
     The optional water resistant coating  20  need only be applied to the rough side  11  of the trigger, although both sides may be coated. The coating should be applied sufficiently thick that the rough side of the sandpaper is covered and remains dry, even when immersed in the supercooled salt solution  40 . A suitable coating is a solvent-free adhesive made of 4,4-diphenylmethane diisocyanate sold under the tradename Supergrip 2000. The size and shape of the trigger is not critical. Typically, the trigger is a disc with a diameter in the range of about 1 to 5 cm. 
     Referring to  FIG. 3 , the trigger is activated by being manipulated by flexing, rubbing or pinching between the thumb and forefinger. The trigger can be activated with one or two hands. When the trigger is manipulated, dry or partially dry particles are released, activating the heat pack. Optionally, the heat pack can be reused by heating the heat pack and reforming the supercooled solution. For re-use, the trigger  200  is flexed again to release additional dry or partially dry particles to retrigger the heat pack. 
     The heat pack of the present invention can be used to heat body parts, such as wrists, ankles, arms and infant heels. In a preferred embodiment, the heat pack has a fastening means for securing the heat pack to a body part. The fastening means can be an elastic band, a contact adhesive applied to the bottom surface of the flexible container, or a strip which encircles the body part. The preferred fastening means is a flexible plastic strip which secures the heat pack to the body part. As shown in  FIG. 4 , a heat pack  100  is applied to the heel and secured with flexible strap  50 . Under either or both ends ( 60  and  70 ) of the strap is an adhesive, such as contact adhesive or pressure sensitive adhesive, which allows the strap to be applied and removed. 
     The invention and its attendant advantages are understood from the foregoing description and it is apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope thereof or sacrificing its material advantages. The arrangements described are merely examples. The claims of the invention are not restricted to the specific forms shown.