Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed...
Patent
1996-04-15
1998-08-04
Nuzzolillo, M.
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
429 54, 429 59, H01M 1002
Patent
active
057890960
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a gas-tight alkaline accumulator.
2. Discussion of Prior Art
The requirements made in respect of accumulators of that kind are progressively rising, in the field of electronics. Continuously increasing mobility and rising demands in regard to operating comfort are compelling the development of ever more powerful, lighter and smaller energy sources. Thus for example hand-held mobile telephones such as the present-day D-network or future E-network telephones are admittedly becoming smaller and smaller and lighter and lighter, but, in order to be able to achieve market successes at all, they must ensure minimum times in respect of operational readiness, which are usually in the range of several hours.
In regard to the development of integrated circuits and very large-scale integrated chip sets for mobile telephones of that kind or other portable equipment such as for example lap-tops or palm-tops (portable computers), camcorders and hearing aids, enormous sums are spent on miniaturising the electronic circuit assemblies, but corresponding small energy sources are also required.
With the development of prismatic casings of plastics material for gas-tight alkaline accumulators, it has already been possible to achieve considerable success in terms of improving those accumulator properties. The use of a light plastic material casing and adaptation of the casing to the geometries which are predetermined by the respective equipment manufacturer or adaptation to wide-spread rectangular casing configurations provide for light accumulators with a high storage density. With adapted electrode shapes, it is possible to use almost the entire remaining volume of the equipment for the storage of electrical charge; reference is directed in this respect to German patent application No P 43 25 464, the disclosed content of which is completely incorporated herein by reference thereto and made the content of the present application.
However, it is precisely in the case of light and small accumulators that a high degree of attention must be paid to the prevention of bursting, in order to avoid unnecessarily losing the advantages attained, by virtue of an additional thickness of material or a more expensive casing structure. In the event of overcharging or charging with excessively high currents, and also after polarity reversal or a short-circuit, high increased pressures may occur in the interior of the casing, and such pressures can ultimately result in bursting of such cells.
Although glass or carbon fibre-reinforced plastic materials have high levels of strength and impact toughness, bursting of the accumulator must be certain to be excluded at any time. Particularly in the case of hand-held items of equipment, the explosive escape of the strongly alkaline and corrosive electrolyte can result in injury to persons and/or damage to expensive items of equipment.
In the case of larger accumulators, to control the increased pressures and the safety risks involved therewith, use is made of screw-in pressure-relief valves which however cannot be used in the case of small gas-tight alkaline accumulators, because of the additional amount of space required for the screwthread and the valve unit which is generally of an expensive construction.
The desired-rupture locations which are known in the field of gas-tight alkaline accumulators with a metal casing are also disadvantageous in regard to damage to high-quality equipment in the event of continuing discharge of the electrolyte. After the desired-rupture location has opened, it continues to result in a loss of sealing integrity of the accumulator casing, and that can therefore involve the undesired discharge of further electrolyte.
SUMMARY OF THE INVENTION
Tests have further shown that such desired-rupture locations used in connection with metal casings cannot be directly transferred to plastic casings. Metal casings, in particular of round cells, can in part withstand pressures of 20 bars and higher, but
REFERENCES:
patent: 4532705 (1985-08-01), Zupanic et al.
patent: 4745039 (1988-05-01), Yoshinaka
patent: 5080983 (1992-01-01), Alexon et al.
patent: 5171647 (1992-12-01), Dean et al.
Christoph Emmerich GmbH & Co. KG
Nuzzolillo M.
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