Chemistry: electrical current producing apparatus – product – and – Means externally releasing internal gas pressure from closed...
Reexamination Certificate
1999-04-16
2001-07-24
Dunn, Tom (Department: 1725)
Chemistry: electrical current producing apparatus, product, and
Means externally releasing internal gas pressure from closed...
C429S171000, C429S185000, C429S056000
Reexamination Certificate
active
06265096
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention generally relates to an electrochemical cell construction. More particularly, the present invention relates to the containers and collector assemblies used for an electrochemical cell, such as an alkaline cell.
FIG. 1
shows the construction of a conventional C sized alkaline cell
10
. As shown, cell
10
includes a cylindrically-shaped can
12
having an open end and a closed end. Can
12
is preferably formed of an electrically conductive material, such that an outer cover
11
welded to a bottom surface
14
at the closed end of can
12
serves as an electrical contact terminal for the cell.
Cell
10
further typically includes a first electrode material
15
, which may serve as the positive electrode (also known as a cathode). The first electrode material
15
may be preformed and inserted into can
12
, or may be molded in place so as to contact the inner surfaces of the can
12
. For an alkaline cell, first electrode material
15
will typically include MnO
2
. After the first electrode
15
has been provided in can
12
, a separator
17
is inserted into the space defined by first electrode
15
. Separator
17
is preferably a non-woven fabric. Separator
17
is provided to maintain a physical separation of the first electrode material
15
and mixture of electrolyte and a second electrode material
20
while allowing the transport of ions between the electrode materials.
Once separator
17
is in place within the cavity defined by first electrode
15
, an electrolyte is dispensed into the space defined by separator
17
, along with the mixture
20
of electrolyte and a second electrode material, which may be the negative electrode (also known as the anode). The electrolyte/second electrode mixture
20
preferably includes a gelling agent. For a typical alkaline cell, mixture
20
is formed of a mixture of an aqueous KOH electrolyte and zinc, which serves as the second electrode material. Water and additional additives may also be included in mixture
20
.
Once the first electrode
15
, separator
17
, the electrolyte, and mixture
20
have been formed inside can
12
, a preassembled collector assembly
25
is inserted into the open end of can
12
. Can
12
is typically slightly tapered at its open end. This taper serves to support the collector assembly in a desired orientation prior to securing it in place. After collector assembly
25
has been inserted, an outer cover
45
is placed over collector assembly
25
. Collector assembly
25
is secured in place by radially squeezing the can against collector assembly
25
. The outer cover
45
is then placed over and in contact with collector assembly
25
. The end edge
13
of can
12
is then crimped over the peripheral lip of collector assembly
25
, thereby securing outer cover
45
and collector assembly
25
within the end of can
12
. As described further below, one function served by collector assembly
25
is to provide for a second external electrical contact for the electrochemical cell. Additionally, collector assembly
25
must seal the open end of can
12
to prevent the electrochemical materials therein from leaking from this cell. Additionally, collector assembly
25
must exhibit sufficient strength to withstand the physical abuse to which batteries are typically exposed. Also, because electrochemical cells may produce hydrogen gas, collector assembly
25
may allow internally-generated hydrogen gas to permeate therethrough to escape to the exterior of the electrochemical cell. Further, collector assembly
25
should include some form of pressure relief mechanism to relieve pressure produced internally within the cell should this pressure become excessive. Such conditions may occur when the electrochemical cell internally generates hydrogen gas at a rate that exceeds that at which the internally-generated hydrogen gas can permeate through the collector assembly to the exterior of the cell.
The collector assembly
25
shown in
FIG. 1
includes a seal
30
, a collector nail
40
, an inner cover
44
, a washer
50
, and a plurality of spurs
52
. Seal
30
is shown as including a central hub
32
having a hole through which collector nail
40
is inserted. Seal
30
further includes a V-shaped portion
34
that may contact an upper surface
16
of first electrode
15
.
Seal
30
also includes a peripheral upstanding wall
36
that extends upward along the periphery of seal
30
in an annular fashion. Peripheral upstanding wall
36
not only serves as a seal between the interface of collector assembly
25
and can
12
, but also serves as an electrical insulator for preventing an electrical short from occurring between the positive can and negative contact terminal of the cell.
Inner cover
44
, which is formed of a rigid metal, is provided to increase the rigidity and supports the radial compression of collector assembly
25
thereby improving the sealing effectiveness. As shown in
FIG. 1
, inner cover
44
is configured to contact central hub portion
32
and peripheral upstanding wall
36
. By configuring collector assembly
25
in this fashion, inner cover
44
serves to enable compression of central hub portion
32
by collector nail
40
while also supporting compression of peripheral upstanding wall
36
by the inner surface of can
12
.
Outer cover
45
is typically made of a nickel-plated steel and is configured to extend from a region defined by the annular peripheral upstanding wall
36
of seal
30
and to be in electrical contact with a head portion
42
of collector nail
40
. Outer cover
45
may be welded to head portion
42
of collector nail
40
to prevent any loss of contact. As shown in
FIG. 1
, when collector assembly
25
is inserted into the open end of can
12
, collector nail
40
penetrates deeply within the electrolyte/second electrode mixture
20
to establish sufficient electrical contact therewith. In the example shown in
FIG. 1
, outer cover
45
includes a peripheral lip
47
that extends upwardly along the circumference of outer cover
45
. By forming peripheral upstanding wall
36
of seal
30
of a length greater than that of peripheral lip
47
, a portion of peripheral upstanding wall
36
may be folded over peripheral lip
47
during the crimping process so as to prevent any portion of the upper edge
13
of can
12
from coming into contact with outer cover
45
.
Seal
30
is preferably formed of nylon. In the configuration shown in
FIG. 1
, a pressure relief mechanism is provided for enabling the relief of internal pressure when such pressure becomes excessive. Further, inner cover
44
and outer cover
45
are typically provided with apertures
43
that allow the hydrogen gas to escape to the exterior of cell
10
. The mechanism shown includes an annular metal washer
50
and a plurality of spurs
52
that are provided between seal
30
and inner cover
44
. The plurality of spurs
52
each include a pointed end
53
that is pressed against a thin intermediate portion
38
of seal
30
. Spurs
52
are biased against the lower inner surface of inner cover
44
such that when the internal pressure of cell
10
increases and seal
30
consequently becomes deformed by pressing upward toward inner cover
44
, the pointed ends
53
of spurs
52
penetrate through the thin intermediate portion
38
of seal
30
thereby rupturing seal
30
and allowing the escape of the internally-generated gas through apertures
43
.
Although the above-described collector assembly
25
performs all the above-noted desirable functions satisfactorily, as apparent from its cross-sectional profile, this particular collector assembly occupies a significant amount of space within the interior of the cell
10
. Because the exterior dimensions of the electrochemical cell are generally fixed by the American National Standards Institute (ANSI), the greater the space occupied by the collector assembly, the less space that there is available within the cell for the electrochemical materials. Consequently, a reduction in the amount of electrochemic
Sondecker George R.
Tucholski Gary R.
Cooke Colleen P.
Dunn Tom
Eveready Battery Company Inc.
Toye, Jr. Russell H.
Welsh Robert W.
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