Surgery: light – thermal – and electrical application – Light – thermal – and electrical application – Thermal applicators
Reexamination Certificate
2001-03-26
2003-03-25
Dvorak, Linda C. M. (Department: 3739)
Surgery: light, thermal, and electrical application
Light, thermal, and electrical application
Thermal applicators
C126S263010, C126S263030
Reexamination Certificate
active
06537309
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a reusable heat pack. The present invention also relates to a trigger device for a heat pack. The invention also relates to a supercooled supersaturated recrystalizable solution for use in heat pack and to a process for the preparation thereof.
BACKGROUND OF THE INVENTION
Use of heating or cooling for many applications has been done by a variety of techniques depending on the specific need. For example, persons suffering from muscular pains normally use rubber bags filled with hot boiling water to alleviate the pain. In case of any head injury normally the doctor's prescription is to apply ice as a first aid. In case of high fever the common house remedy has been to apply a cloth soaked in cold water on the forehead to bring down the temperature. Many a time on a recreational trip people tend to take packed food or even carry cooking apparatus and the raw, materials for cooking food. The other need of heat energy is in the remote areas where availability of the fuels may not be possible or may be very expensive. Therefore to get over all these difficult situations it is necessary to devise ways and means to generate heat in an economical way and preferably without the use of conventional fuels. To address this very need, development of device called the heat pack has occurred over the past 15 years. The main principle underlying the heat pack is to use heat generated due to a start of a chemical reaction between two or more chemicals or due to triggering of initiation of crystallization of a supercooled chemical solution. In the context of the present invention it is the second aspect which is disclosed
Several warming materials are available in the market such as hot water bag, portable electrical bag warmer or battery operated warmer. However, in case of hot water bag, hot water is to be poured in the bag which can only be obtained either by using fuel or electrical energy. Further the heat of the water bag does not last long enough for giving any observable effect. In case of electrical bag warmer a permanent supply of electricity is needed. This limits the use of this heating device to only such places where there is electricity available i.e only indoors. In case of battery operated warmer the battery needs to be charged regularly and needs replacement as and when it gets exhausted. In all these cases another drawback is that the use is very limited and safety precautions need to be taken in case of electrical heat packs.
A non-conventional heat pack has been disclosed in a U.S. Pat. No. 4,532,110(1985). In this disclosure heat energy is generated by a trigger action on a supercooled saturated solution of sodium acetate. The triggering is accomplished by a specially designed device. The entire assembly of trigger and the supercooled solution is kept in a plastic container made of PVC, polyurethane or the like. The drawback in the invention is that the trigger used to initiate the crystallization of the super cooled sodium acetate solution has to have a protective layer of gold or silver to prevent any corrosion due to contact with the chemical. This is not desirable since the material used for the trigger is already an expensive CuBe alloy. Further the PVC material for the heat pack manufacturing has a very limited shelf life due to inevitable leaching of the chloride ion due to the presence of sodium salt solution. This drawback is present in the other disclosed inventions as well as disclosed in U.S. Pat. Nos. 4,572,158; 5,058,563 and 5,205,278. A further drawback in the disclosed inventions, except in U.S. Pat. No. 5,058,563, is that the supercooled solution tends to flow to one side giving rise to uneven heating effects thereby rendering the heat pack difficult to use by needing to adjust the contour of the pack for a particular application before initiation of crystallisation and resultant heat generation.
In U.S. Pat. No. 5,058,563 use has been made of an additive to induce gelation during crystallisation. This gelation helps in maintaining the desired density of the solution and hence uniformity of heat over the entire useful area. The gelation material used in the said disclosure is a water soluble hydroethyl cellulose polymer. This material though giving the advantage of gelling the solution suffers from the disadvantage of being unstable, thereby rendering the heat pack in capable of reuse.
U.S. Pat. No. 5,843,145 discloses a reusable heat pack wherein a mixture of three constituents forming a gel, is sealed in a plastic bag. This reusable heat pack needs an external heating or cooling means to give a useful application of the device. In case of heating application, the heat pack is put in a microwave oven or any other heating means to energise the pack. It is claimed that the temperature of the heat pack is maintained for a sufficient length of time thereby claiming its use as a heat pack. In view of the fact that the pack needs an external heating means, the invention proves to be disadvantageous in its claimed use as a heat pack. This is mainly due to the fact that in the invention discloses that the preconditioning of the pack is to be done for a time period typically two hours. This renders the pack as disclosed not advantageous in an emergency practical situation and also in remote areas, where heating means such as microwave oven may not be available.
JP 58180575 discloses a cooling pack with a mixture provided therein containing inter alia, aniline chloride. However, in this disclosure, the mixture acts as an endothermic material wherein the material when dissolved in water absorbs heat and produces a cooling effect.
The present invention circumvents the drawbacks of the inventions of the prior art.
Objects of the Invention
An object of the present invention is to provide a reusable heat pack which obviates the drawbacks mentioned above.
Another object of the invention is to provide a heat pack with a shelf life of at least six months.
A further objective of the present invention is to provide a heat pack which can be recycled at least a hundred times.
Still another objective of the present invention is to provide a heat pack with heat retention for at least two hours.
Yet another object of the present invention is to provide a heat pack capable of being used for therapeutic application.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a reusable heat pack, which comprises a soft sealed plastic bag containing a mixture of supercooled supersaturated recrystalizable solution of inorganic substance, alcohol, chemical compound additives, and means to trigger recrystallization of supercooled supersaturated recrystalizable solution of inorganic substance.
In an embodiment of the invention the plastic bag is made of polypropylene or polyvinyl chloride.
In another embodiment of the invention, the inorganic substance is selected from sodium acetate and calcium nitrate.
In still another embodiment of the present invention the supercooled supersaturated recrystalizable solution of inorganic substance is made in good quality water.
In a further embodiment of the invention, the good quality water is bacteria free municipal supply or distilled water.
In a further embodiment of the present invention the alcohol is selected from ethylene glycol and glycerol.
In yet another embodiment of the present invention the chemical additive comprises an organic amine.
In a further embodiment of the invention, the organic amine comprises aniline.
In another embodiment of the invention, the supercooled supersaturated recrystalizable solution comprises a mixture of hydrated salt of sodium acetate 50-70 wt %, ethylene glycol 1-10 wt %, aniline 10-20 wt % and water 10-29 wt %.
In another embodiment of the present invention the means for triggering recrystallization comprises a mechanical device selected from the group consisting of crocodile clip and a safety pin.
In a further embodiment of the present invention the material of the means for trigger comprises a noncorrosive material.
In a further embodimen
Kant Chandra
Sarkar Ajit Kumar
Sharma Chattrapal
Sharma Rajendra Kumar
Council of Scientific and Industrial Research
Dvorak Linda C. M.
Ladas & Parry
Schopfer Kenneth G
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