Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Patent
1994-06-16
1995-12-26
Kalafut, Stephen
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
429180, 429181, H01M 208
Patent
active
054786690
DESCRIPTION:
BRIEF SUMMARY
This application is a national phase application of PCT/CA92/00550, published as WO 93/12549.
FIELD OF THE INVENTION
The invention relates to a cylindrical cell with improved closure assembly.
BACKGROUND OF THE INVENTION
The leakage proof closure of cylindrical cells with an aqueous alkaline electrolyte solution has long been the objective of research and development activity, as can be demonstrated by a large number of patents. The different cell closure types of commercially available cylindrical cells released by major manufacturing companies embody the most up to date technical solutions.
The available cell closure assemblies have the following main common properties: terminal of cells. The cap has a disc-like central portion, and a flange portion extending towards the interior of the cylindrical can; and for providing a sealing gasket. In most designs, a blow out vent is provided in the plastic top that ruptures if the inner gas pressure exceeds a predetermined limit; the inner surface of a gasket zone of the can, and provides a tight sealing between the can and the plastic top if a sufficiently large pressure is maintained between the contacting surfaces to be sealed; of the plastic top provides electrical insulation between the can and the flange. The crimped metal has the task of maintaining the pressure required between the can and the critical portion of the plastic top for a leakage proof sealing.
In LR6 (North American AA) type cells manufactured by Union Carbide Corporation, the flange of the negative cap has a sharp circular edge, and the crimping pressure of the can acts on the outer side of an outer cylindrical portion of the plastic top which is supported from the inside by this edge and by the edge of a washer. The crimping step should be performed carefully, since in case of higher forces the circular edge of the flange can cut through the thin plastic wall and a short circuit will be experienced.
The pressure distribution along this thin plastic wall is uneven, and the maximum pressure is limited by the load bearing ability of the plastic material. After longer use or at elevated temperatures the resiliency of thermoplastic materials decreases, whereby the quality of the sealing can worsen.
In the closure assembly of LR6 cells manufactured by DURACELL Inc., the negative cap is separated from a resilient metal disc used to support the inner wall of the plastic outer cylinder of the plastic top pressed from outside by the crimped can. An outwardly bent portion of the disc presses the wall out in a radial direction; however, an outwardly projecting edge exerts shearing load on the wall of the plastic material. In case of higher pressures this edge might cut the thin plastic wall. The design is capable of providing radial forces only.
In the closure assembly of LR6 cells manufactured by FUJITSU Inc., the negative cap also has an outwardly and upwardly bent flange portion, and the crimping of the can bends the thin plastic wall over this portion so that the upper edge of the bent flange portion is pressed against the thin plastic wall. The edge to wall attachment between a metal and a plastic material is made in such a way that at higher load the edge might tend to cut through the plastic wall, so that such loads should be avoided. This closure assembly is capable of maintaining a radial bias only.
There are a number of other closure designs which combine the aforementioned principles only, and for that reason they also have limited long term leakage proof properties.
The problem of appropriate cell closure acquires an increased significance in mercury free cell technique, since mercury was an efficient material which reduced gassing within the cells. In mercury free cells, specific measures should be taken for reducing hydrogen formation and for recombining any evolved hydrogen gas.
It is the primary object of the present invention to provide a cell closure assembly which has improved performance; i.e. which can provide a better sealing effect and in which the hazard of cell shorts ar
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patent: 3694267 (1972-09-01), Angelovich
patent: 4227701 (1980-10-01), Tsuehida et al.
patent: 5080985 (1992-01-01), Wiacek et al.
patent: 5150602 (1992-09-01), Payne et al.
patent: 5272020 (1993-12-01), Flack
Battery Technologies Inc.
Hewson Donald E.
Kalafut Stephen
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