Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
1997-07-25
2001-06-19
Nuzzolillo, Maria (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S168000, C429S167000, C429S163000, C429S164000, C429S166000
Reexamination Certificate
active
06248473
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to a battery cell construction, and more particularly relates to a positive cover for an alkaline battery cell.
Current alkaline batteries are typically constructed in the manner shown in
FIGS. 1 and 2
. Specifically, alkaline battery
10
includes a steel can
15
having a cylindrical shape with one open end. A metalized, plastic film label (not shown) is formed about the exterior surface of steel can
15
except for the ends of steel can
15
. At a closed end
14
of steel can
15
is a positive cover
17
preferably formed of plated steel. A cathode
20
, preferably formed of a mixture of manganese dioxide, graphite, potassium hydroxide solution, deionized water, and a TEFLON™ solution, is formed about the interior side surface of steel can
15
. A separator
30
, which is preferably formed of a non-woven fabric that prevents migration of any solid particles in the battery, is disposed about the interior surface of cathode
20
. An electrolyte formed of potassium hydroxide, is disposed in the interior of separator
30
. An anode
50
, preferably formed of zinc powder, a gelling agent, and other additives, is disposed within an electrolyte in contact with a current collector
60
, which may be formed of brass. Current collector
60
contacts a brass rivet
70
projecting through a nylon seal
71
formed at the open end of steel can
15
to prevent leakage of the active ingredients contained in steel can
15
. Nylon seal
71
contacts a metal washer
72
and an inner cell cover
74
, which is preferably formed of steel. A negative cover
75
, which is preferably formed of a plated steel, is disposed in contact with inner cell cover
74
and brass rivet
70
. Rivet
70
contacts current collector
60
through a hole formed in nylon seal
71
. Negative cover
75
is electrically insulated from steel can
15
by nylon seal
71
.
Positive cover
17
includes a protruding nub
18
at its center which forms the positive contact terminal of the battery. As shown in
FIG. 1
, positive cover
17
has a diameter that is substantially equal to the diameter of cylindrical steel can
15
. Positive cover
17
contacts the closed end
14
of steel can
15
about its peripheral edge. Because the cell may bulge during storing, discharge, etc. and because positive cover
17
is rigid and inflexible, a gap
19
is provided between the inner surface of positive cover
17
and the exterior surface of closed end
14
of approximately 0.022 inch to allow for such bulging. The positive cover
17
can be fastened to the container by welds
42
after the cathode is rammed into place.
As shown in
FIG. 2
, positive cover
17
further includes a reinforcing rib
16
, which protrudes outward about a peripheral edge of cover
17
. In the assignee's current design, this reinforcing rib protrudes a little more than 0.042 inch from the outer surface of the closed end
14
of can
15
. Further, the outer surface of positive contact terminal
18
extends an additional 0.090 inch from the outer surface of reinforcing rib
16
in the current design.
A primary goal in designing alkaline batteries is to increase the service performance of the cell. The service performance is the length of time for the cell to discharge under a given load to a specific voltage at which the cell is no longer useful for its intended purpose. One approach taken to increase service performance was to increase the interior volume of the cell in order to increase the amount of active materials within the cell. However, the commercial external size of the cell is fixed, thereby limiting the ability to increase the amount of active materials within the cell. For example, the cell length from the end of positive contact terminal
18
to the exterior surface of negative cover
75
is fixed by standards as well as the height of the protrusion that forms positive contact terminal
18
.
In order to accommodate more active materials within the cell while maintaining the external size of the cell, the steel label and insulating paper tube of the original alkaline cell has been replaced with one made of thinner metalized plastic film. Thus, the steel can may be enlarged to provide a greater internal volume. By switching to a thinner plastic film label, the service performance of a typical alkaline cell was significantly increased. Another approach taken to increase the service performance of a cell is to provide for better utilization of the electrode materials. This approach is taken in U.S. Pat. No. 5,501,924 issued to Wendi Swierbut et al., which discloses utilizing tin dioxide as an additive to a cathode. Despite past increases in service performance, the need to find new ways to increase service performance remains the primary goal of cell designers.
SUMMARY OF THE INVENTION
The present invention improves the service performance of alkaline cells by further increasing the internal volume of the cell. To achieve this and other advantages, and in accordance with the purpose of the invention as embodied and broadly described herein, the present invention provides a composite cover assembly for the closed end of the cylindrical can of an electrochemical cell that includes an electrically conductive contact terminal having a diameter substantially smaller than the diameter of the cylindrical can, and a flexible disk-shaped label that covers the portion of the surface of the closed end of the can that is not covered by the contact terminal. By using a smaller contact terminal, the gap
19
(
FIG. 1
) provided between the positive cover
17
and the closed end
14
of can
15
to accommodate cell bulging in the conventional construction, may be substantially eliminated and the length of the can may be increased without exceeding the standards established for overall battery length. In addition, by eliminating the reinforcing rib on the positive cover, the internal cell volume may be further increased while maintaining the 0.090 inch protrusion distance of the positive contact terminal.
More specifically, the electrochemical cell of the present invention comprises a cylindrical can for containing at least an anode and a cathode, the cylindrical can having one open end and one closed end. The electrochemical cell further includes a first contact terminal assembly mounted within the open end of the cylindrical can in electrical isolation therefrom, and a protruding second contact terminal mounted in electrical contact to the closed end of the cylindrical can, the second contact terminal covering less than all of an exterior surface of the closed end of the cylindrical can. Preferably, the first contact terminal assembly is a negative contact terminal assembly that is electrically coupled to the anode and the second contact terminal is a positive contact terminal that is electrically coupled to the cathode. The electrochemical cell may further include an end cover label mounted to the exterior surface of the closed end of the cylindrical can and covering that portion of the exterior surface not covered by the second contact terminal.
These and other features, objects, and benefits of the invention will be recognized by those who practice the invention and by those skilled in the art, from reading the following specification and claims, together with reference to the accompanying drawings.
REFERENCES:
patent: 2411272 (1946-11-01), Keller
patent: 3701689 (1972-10-01), Karobath et al.
patent: 4002808 (1977-01-01), Fafa
patent: 4079172 (1978-03-01), Potts et al.
patent: 4084045 (1978-04-01), Kegelman
patent: 4726779 (1988-02-01), Costenoble et al.
patent: 5173371 (1992-12-01), Huhndorff et al.
patent: 5464705 (1995-11-01), Wainwright
patent: 5501924 (1996-03-01), Swierbut et al.
patent: 5585207 (1996-12-01), Wakabe et al.
patent: 973083 (1951-02-01), None
patent: 1097049 (1955-06-01), None
patent: 2104613 (1972-04-01), None
patent: 2262415 (1975-09-01), None
patent: 2342561 (1977-09-01), None
patent: 2680132 (1993-02-01), None
patent: 740218 (1955-11-01), None
Eveready Battery Company Inc.
Nuzzolillo Maria
Ruthkosky Mark
Toye, Jr. Russell H.
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