WO1997000055A1

WO1997000055A1 - A device for heating or cooling a body part

Info

Publication number: WO1997000055A1
Application number: PCT/AU1996/000352
Authority: WO
Inventors: Peter Lawrence Murphy; Terry Howard Solomon
Original assignee: Thermal Energy Accumulator Products Pty. Ltd.
Priority date: 1995-06-15
Filing date: 1996-06-12
Publication date: 1997-01-03
Also published as: AUPN358495A0

Abstract

The present invention relates generally to a device (10) comprising a container (12) sealably containing a phase change substance (14) having a relatively high latent heat of fusion. The device (10) can be used for either heating or cooling a body part. The container (12) comprises a first and a second mutually opposing sheet (16, 18) joined around their peripheral edges (20). A chamber (22) is thus formed between the first and second sheets (16, 18). The chamber (22) of the container (12) is filled with the phase change substance (14) during manufacture of the device (10). When the device (10) is used for heating the hydrate salt sodium acetate trihydrate may be used, having a melting point of approximately 58 °C. On the other hand, when the device (10) is used for cooling a phase change substance such as a stoichiometric mixture of ammonium bicarbonate, ammonium chloride, and demineralised water having a melting point of approximately -4 °C may be used. The device is then either heated or cooled so the phase change substance either melts or crystallises. The device (10) is then manually applied to a persons skin and the phase change substance as it either chrystallises or melts, releases or absorbs heat thus heating or cooling the body part. The device (10) provides either heating or cooling which is effective over a relatively long period of time. Furthermore, the device (10) provides an effective means for heating or cooling safely using latent heat without the risk of being burnt or scalded by sensible heat.

Description

A DEVICE FOR HEATING OR COOLING A BODY PART

FIELD OF THE INVENTION

The present invention relates generally to a device for heating or cooling a body part and relates particularly, though not exclusively, to a device adapted for remedial or therapeutic heating or cooling by manually applying the device to a person's skin.

BACKGROUND TO THE INVENTION

A rubber bottle having a screw cap for sealably containing hot water, commonly known as a hot water bottle, is used to heat a person's feet while they are in bed. Heating is effected by the specific or sensible heat of the hot water being absorbed by the feet via the rubber bottle. Specific heat for water is relatively low, approximately one (1) kilocalorie/litre (kcal/1) , and thus effective heating is provided for a relatively short period. Furthermore, hot water has the potential to burn or scald a person if the bottle is not adequately insulated or sealed to safeguard against this problem.

Plastic containers designed to hold ice or iced water, commonly known as ice packs, are used during physiotherapy treatment for muscular aches and pains. In use, the ice pack is applied directly to the skin of a person and the person's muscles are thus contracted by the chilling or cooling effect of the ice or iced water. However, body heat together with ambient heat melt the ice and thus the ice pack is effective for a relatively short period.

SUMMARY OF THE INVENTION

An intention of the present invention is to provide a device for heating or cooling a body part that is effective in use for a relatively long period. According to the present invention there is provided a device for either heating or cooling a body part, said device comprising: a container adapted to be heated or cooled by an external heat source; and a phase change substance, having a relatively high latent heat of fusion, sealably contained within the container whereby, in use, at least a portion of said phase change substance can be either substantially fused or crystallised using the external heat source, and thereafter the container contacted with a body part so that latent heat is either released from or absorbed by the phase change substance, as the substance either crystallises or fuses, and the body part is either heated or cooled, respectively.

Typically, the phase change substance is hermetically sealed within the container. Preferably, the container is constructed of a resilient material so that, in use, when a portion of the container is contacted with a body part, said portion is resiliently deformed to substantially contour to the body part for effective heat transfer therewith. Typically, the container is constructed of a material having relatively low thermal conductivity so that, in use, the period during which the phase change substance remains in either the liquid or solid phase is substantially maximised thereby providing effective heating or cooling for a relatively long period. In one example, the material is a synthetic rubber material.

Typically, when the device is to be used for heating, the container is adapted to be heated in an oven so that, in use, the phase change substance is substantially fused in said oven. Preferably, the oven is a microwave oven. Alternatively, when the device is to be used for cooling, the container is adapted to be cooled in a refrigerator so that, in use, the phase change substance is substantially crystallised in said refrigerator. Typically, the phase change substance is a hydrate salt or a derivative thereof having a relatively high latent heat of fusion. Preferably, when the device is used for heating, the hydrate salt has a melting point of between approximately 30°C to 70°C. In one such example the hydrate salt is sodium acetate trihydrate or a derivative thereof, having a melting point of approximately 58°C. Alternatively, when the device is used for cooling, the hydrate salt has a melting point of between approximately -10°C to 5°C. In one such example the hydrate salt is a substantially stoichiometric mixture of ammonium bicarbonate, ammonium chloride, and demineralised water, having a melting point of approximately -4°C.

Preferably, the container comprises one or more sheets arranged so as to define a chamber in which the phase change substance is contained. Typically, the volume of the chamber is less than approximately one (1) litre. Typically, the chamber is substantially full of said phase change substance. It is believed that by reducing the volume of phase change substance within the chamber that the number of phase change cycles the substance can effectively perform is significantly increased. In another embodiment at least a portion of an external surface of the container is ribbed or textured to provide an increased surface area for heat transfer to the body part via the container. Furthermore, the ribbed or textured external surface insulates the phase change substance from ambient temperature conditions and thus maximises the period during which the phase change substance remains in either the liquid or solid phase.

Typically, the device is adapted for direct heating or cooling of the skin of a human body. In one example the device is adapted to be used on the human body part such as in physiotherapy treatment. Alternatively, the device is designed for remedial heating or cooling of the human body part such as for warming a person's feet. BRIEF DESCRIPTION OF A DRAWING

In order to achieve a better understanding of the nature of the present invention a preferred embodiment of a device for heating or cooling a body part will now be described, in some detail, by way of example only, with reference to the accompanying drawing in which:

Figure 1 is a perspective view of a device for heating or cooling a body part, the device cut transversely.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

As shown in Figure 1 there is a device 10 for heating or cooling a body part (not shown) , the device 10 comprising a container 12 sealably containing a phase change substance, in this example a hydrate salt 14. The hydrate salt 14 has a relatively high latent heat of fusion.

The hydrate salt 14 of this example is either: i) sodium acetate trihydrate or a derivative thereof; or ii) a stoichiometric mixture of ammonium bicarbonate, ammonium chloride, and demineralised water depending on the application.

When the device 10 is to be used for heating the sodium acetate trihydrate salt is used, and when the device is to be used for cooling the hydrate salt containing ammonium bicarbonate and ammonium chloride is used. It will be appreciated however that a variety of phase change substances may be used depending on whether heating or cooling is required. Furthermore, the choice of phase change substance will also depend on what temperature the heating or cooling is required which is dictated largely by the melting point of the phase change substance. Sodium acetate trihydrate has a melting point of approximately 58°C, and the hydrate salt containing a stoichiometric mixture of ammonium bicarbonate, ammonium chloride and demineralised water has a melting point of approximately - 4°C.

The container 12 comprises a first and a second mutually opposing sheet 16, 18, respectively, of substantially the same shape and size. The first and second sheets 16, 18 are joined around opposing peripheral edges 20 of each sheet 16, 18. In this example, the container 12, and the first and second sheets 16, 18 are substantially rectangular in shape. The opposing sheets 16, 18 are joined together by heat sealing adjacent the peripheral edge 20. A chamber 22 is thus formed between the first and second sheets 16, 18. In this example, the chamber 22 has a volume of approximately one (1) litre.

An upper surface of the first sheet 16 has a series of parallel ribs 24 extending longitudinally along the first sheet 16. The ribs 24 are formed integral with the first sheet 16. In this example, the first and second sheets 16, 18, and thus the container 12 is constructed of a synthetic rubber material. Advantageously, the synthetic rubber material is resilient and has relatively low thermal conductivity.

The chamber 22 of the container 12 is filled with the hydrate salt 14 during manufacture of the device 10. In this example, the hydrate salt 14 is hermetically sealed within the chamber 22, and the chamber 22 is substantially full of the hydrate salt 14. In an alternative embodiment, the container 12 may comprise an opening through which a phase change substance can be poured. In this alternative embodiment, a closure meanε, such as a screw cap, is connected to the container so as to sealably contain the phase change substance within the container.

Operation of the device 10 described above will now be explained, in some detail, when used either for heating or cooling a body part (not shown) . When the device 10 is used for heating the hydrate salt 14 sodium acetate trihydrate is used, having a melting point of approximately 58°C. The device 10 containing the phase change substance 14, is placed in a microwave oven and heated so that substantially all of the hydrate salt 14 fuses. Heating in a domestic microwave oven, rated from between 800 to 1000 kW, is required for between approximate seven (7) to ten (10) minutes for one (1) litre of sodium acetate trihydrate. The device 10 is then removed from the microwave oven and preferably the externally ribbed surface of the first sheet 16 contacted with the skin of a person. As the hydrate salt 14 gradually crystallises, under ambient temperature conditions, latent heat is released from the hydrate salt 14 and the person's skin is heated via the ribbed first sheet 16.

Trials performed, with the device 10 containing approximately one (1) litre of sodium acetate trihydrate, have shown that heat effective for warming the skin is evolved for between four (4) to seven (7) hours. The surface temperature of the container 12 is maintained at approximately 50°C over this period.

In this example, where the container 12 is constructed of a synthetic rubber material having relatively low thermal conductivity, the period during which the hydrate salt 14 remains in the liquid phase is substantially maximised. Effective heating of the skin is thus provided for a relatively long period. Furthermore, the parallel ribs 24 located on the first sheet 16 increase the surface area of the container 12 for effective heat transfer to the skin. Because the container 12 is constructed of a resilient material the device 10 can be wrapped or contoured around a body part to be treated which provides increased heat transfer between the hydrate salt 14 and the skin. The device 10 may be used for a variety of applications where heating or cooling of a body part is required. For example, the device 10 may be used for heating of a person's feet in bed as a substitute for a known hot water bottle. In this application, the device 10 is believed to provide heating for a period of at least twelve (12) hours.

The device 10, when used for cooling a body part, comprises a phase change substance, such as a stoichiometric mixture of ammonium bicarbonate, ammonium chloride, and demineralised water, with a relatively low melting point. In this example, the melting point of the hydrate salt including ammonium bicarbonate and ammonium chloride is approximately -4°C. The device 10 is placed in a refrigerator so that the hydrate salt 14 within the container 12 substantially crystallises. The device 10 can then be removed from the refrigerator and applied to a person's skin for cooling of the skin. As the hydrate salt 14 fuses having a melting point of approximately -4°C, the hydrate salt 14 absorbs heat from the skin which is thus cooled. The device 10 can be manually applied to a person's skin for therapeutic treatment of muscular aches and/or pains .

The container 12, constructed of a relatively high heat insulation material, retards the rate at which the hydrate salt 14 fuses and thus provides effective cooling for a relatively long period. Furthermore, the container 12 is designed so that it can be wrapped or contoured around the skin of a person so that effective heat transfer is provided between the device 10 and the person's skin.

Now that a preferred embodiment of the present invention has been described in some detail it will be apparent to those skilled in the relevant arts that the device for heating or cooling a body part has at least the following advantages over the admitted prior art: (i) the device provides either heating or cooling which is effective over a relatively long period of time; and (ii) the device provides an effective means for heating or cooling safely using latent heat without the risk of being burnt or scalded by sensible heat.

It will be appreciated that the present invention is not limited to the embodiments described above, and that numerous variations and modifications can be made to the device for heating or cooling a body part which are considered to be within the ambit of the present invention. For example, the container is not restricted to the shape and configuration described herein but may be of practically any shape so long as the container sealably contains a phase change substance, and the substance can be heated or cooled by a heat source, such as a microwave oven or a refrigerator, respectively. Furthermore, the container need not be resilient as described herein. The container may also be constructed of a material having relatively high thermal conductivity where rapid heat transfer over a somewhat shorter period of time is required. The present invention is not limited to any of the applications described herein but may extend to any application for heating or cooling a body part. The device is not restricted to application on humans but may also be used on animals. All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A device for either heating or cooling a body part, said device comprising: a container adapted to be heated or cooled by an external heat source; and a phase change substance, having a relatively high latent heat of fusion, sealably contained within the container whereby, in use, at least a portion of said phase change substance can be either substantially fused or crystallised using the external heat source, and thereafter the container contacted with a body part so that latent heat is either released from or absorbed by the phase change substance, as the substance either crystallises or fuses, and the body part is either heated or cooled, respectively.

2. A device for either heating or cooling a body part as defined in claim 1 wherein the phase change substance is hermetically sealed within the container.

3. A device for either heating or cooling a body part as defined in either claim 1 or 2 wherein the container is constructed of a resilient material so that, in use, when a portion of the container is contacted with a body part, said portion is resiliently deformed to substantially contour to the body part for effective heat transfer therewith.

4. A device for either heating or cooling a body part as defined in any one of the preceding claims wherein the container is constructed of a material having relatively low thermal conductivity so that, in use, the period during which the phase change substance remains in either the liquid or solid phase is substantially maximised thereby providing effective heating or cooling for a relatively long period.

5. A device for either heating or cooling a body part as defined in claim 4 wherein the material from which the container is constructed is a synthetic rubber material.

6. A device for either heating or cooling a body part as defined in any one of the preceding claims wherein the phase change substance is a hydrate salt or a derivative thereof having a relatively high latent heat of fusion.

7. A device for heating a body part as defined in claim 6 wherein the hydrate salt has a melting point of between approximately 30°C to 70°C.

8. A device for heating a body part aε defined in claim 7 wherein the hydrate salt is sodium acetate trihydrate or a derivative thereof, having a melting point of approximately 58°C.

9. A device for cooling a body part as defined in claim 6 wherein the hydrate salt has a melting point of between approximately -10°C to 5°C.

10. A device for cooling a body part aε defined in claim 9 wherein the hydrate εalt iε a εubεtantially stoichiometric mixture of ammonium bicarbonate, ammonium chloride, and demineralised water, having a melting point of approximately -4°C.

11. A device for either heating or cooling a body part as defined in any one of the preceding claims wherein the container comprises one or more sheets arranged so as to define a chamber in which the phase change substance is contained.

12. A device for either heating or cooling a body part as defined in claim 11 wherein the volume of the chamber is less than approximately one (1) litre.

13. A device for either heating or cooling a body part as defined in any one of the preceding claims wherein at least a portion of an external surface of the container is ribbed or textured to provide an increased surface area for heat transfer to the body part via the container.

14. A device for either heating or cooling a body part as defined in claim 13 wherein the ribbed or textured external surface is designed to insulate the phase change substance from ambient temperature conditions and thus maximise the period during which the phase change substance remains in either the liquid or solid phase.