Electric resistance heating devices – Heating devices – With heat storage means
Patent
1998-10-20
2000-03-28
Jeffery, John A.
Electric resistance heating devices
Heating devices
With heat storage means
219530, 12626305, C09K 500, C09K 506
Patent
active
060442018
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device for storing and gradually dispensing heat or cold, comprising a container having an at least partially heat-conducting wall which encloses a space in which a material having a high heat capacity is present.
DESCRIPTION OF THE RELATED ART
Such devices are known. A known example is a hot-water bottle, usually a sealable metal or rubber shell which is filled with hot water. Such bottles may leak and therefore carry the risk of scalding by the hot water. Particularly in the case of babies, the sick or the elderly this presents an unacceptable risk.
Safer alternatives to the hot-water bottle have been investigated for some time now. Thus, EP-A-290240 describes an electric heating device which consists of a block containing mineral powder in a polymer matrix and contained therein a heating element and the required electrical leads. In this case there is no risk of leakage, but the limited heat capacity and the high weight form drawbacks.
GB-A-2192118 discloses a bed heater which consists of a flexible container which is made of rubber or an elastomer and which contains a vegetable oil and is provided with electric heating means. The heat capacity of this heater is lower than that of a water bottle, and there is a similar risk of leakage.
U.S. Pat. No. 3,840,985 discloses a water bed heater which consists of two layers of styrene-butadiene rubber with electric heating wires installed in between these. In view of, among other factors, the low heat capacity, such a heater is virtually unsuitable as a heat-chargeable device.
SUMMARY OF THE INVENTION
We have now found a device for storing and dispensing heat or cold, which has a high heat capacity and cannot leak. The device according to the invention is characterized in that the material having a high heat capacity comprises a hydrogel formed by a hydrophilic polymer which contains or is able to contain 50-99.5 wt % of water, based on the sum of polymer and water.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a plan view of the device and FIG. 2 is a cross-sectional view along II--II.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The device according to the invention is not limited to being used as a substitute for hot-water bottles, but can also be used for the purpose of keeping meals, drinks and other materials and aids warm or cool.
With reference to FIG. 1, the container (1) of the device may be made of any suitable material. What matters is only that the wall material (2) will withstand the temperatures at which it is used. Suitable materials are polyamide (PA, nylon), polycarbonate (PC), polyethylene terephthalate (PET), poly(ethylenenaphthalene) (PEN) and poly(oxymethylene) (POM). The container can then be shaped by, for example, blow-moulding, casting or extrusion. The material may also be a heat-resistant rubber or a metal, such as aluminium, stainless steel or chromium copper. It is also possible to use a metal (3) with a plastic coating (4) on top of it. The shape of the container can be varied without restrictions. Examples are cylinders, flat, triangular or square blocks, possibly rounded off, discs, rolls and the like. The container may also have the shape of a bowl or trough, so that materials are able to come into contact with the device on more than one side.
The hydrogel (5) is formed by a hydrophilic polymer which, as a result of hydrogen bond formation, has pronounced water-binding characteristics. The hydrophilic polymer can absorb at least its own weight in water. Preferably it can contain 75-99.5 wt %, in particular 90-99 wt % of water, based on the sum of polymer and water. The structure of the hydrophilic polymer must be such that the hydrogen bonds remain intact up to a temperature of about 80.degree. C., preferably up to at least 90.degree. C. Optionally, a hydrophilic organic solvent such as an alcohol, acetone, glycol, glycerol or polyglycol may also be present, but preferably less than 20 wt %, in particular less than 5 wt %, of this is present, based on the water.
In
REFERENCES:
patent: 4042012 (1977-08-01), Perry et al.
patent: 4209413 (1980-06-01), Kent et al.
patent: 4273667 (1981-06-01), Kent et al.
patent: 4619778 (1986-10-01), Chalk et al.
patent: 5423996 (1995-06-01), Salyer
Jeffery John A.
Technische Universiteit Delft
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