Coating processes – Electrical product produced
Reexamination Certificate
1999-03-17
2001-08-07
Walker, W. L. (Department: 1723)
Coating processes
Electrical product produced
C427S121000, C427S179000, C427S421100, C493S308000, C429S133000
Reexamination Certificate
active
06270833
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates in general to an alkaline cell and more particularly to a separator for the alkaline cell and a method of producing the separator.
Generally known alkaline cells such as LR-6 type alkaline cells have, as illustrated in
FIG. 1
, a cylindrical casing
2
having a bottom end for serving as a cathode, an electrically conductive membrane (not shown), three cylindrical cathode mixes
3
piled within the cathode cylindrical casing
2
, a cylindrical separator
4
having a bottom end, an electrolyte in both the separator
4
and the cathode mixture
3
, and an anode active mass
5
of zinc in the form of gel.
The cathode metal casing
2
has an opening to which a closure body
6
is mounted snugly. The sealing body
6
has an anode terminal
7
, a current collector
8
fixed to an inner central portion of the anode terminal plate
7
by spot welding and the like, a gasket
9
fitted to the current collector
8
with a sealing material disposed therebetween, and an annular sealing cap
11
firmly fitted to the opening of the cathode casing
2
. When the current collector
8
is inserted into the anode active mass
5
of gel-like zinc anode material
5
, an end
4
A of the separator
4
is pressed inside by the gasket
9
to be bent inside, and while the separator end
4
A is bent inside, an end of the opening of the cathode casing
2
is caulked and an outer circumferential portion of the gasket
9
is clamped between the outer circumferential portion of the anode terminal plate
7
and an end of the cathode casing
2
, so that the opening of the cathode casing
2
is sealed by the closure body
6
.
On an outer surface of the cathode metal casing
2
, there is provided a label
12
which has recently replaced the conventional metal jacket for the purpose of increasing the inner volume of the cell and referred to as “shrink tack label” or simply “label”, and an annular anode washer
13
is disposed between an outer circumferential portion of the anode terminal plate
7
and the label
12
.
With reference to
FIG. 2
, the separator
4
has been produced by rotating a roll
20
of a base paper
21
for the separator by pulling an end of the roll paper in its longitudinal direction and cut into a predetermined length in accordance with a length (height) of a separator to be formed, and then the base paper
21
of the predetermined length is rotated in the horizontal direction in the drawing by means of a mandrel (not shown) to form a cylindrical structure as illustrated. The cylindrical base paper
21
is then heat-bonded at its side portion and bottom portion to form a cylindrical structure having a closed bottom end. This conventional method of producing the separator base paper
21
must be turned at right angle to change its moving direction from the cutting step to a winding step in which the cut base paper is wound and adhered to form a cylindrical structure and its production rate is limited at most to 100 pieces per minute.
Therefore, if it is necessary to produce about 600 separators
4
per minute, as shown in
FIG. 3
, a roll
20
of a separator base paper
21
is rotated in the horizontal direction to pull the base paper in the longitudinal (horizontal) direction and then cut into a predetermined length, and the cut base paper is rotated in the horizontal direction by using a mandrel wound into a cylindrical form, and then the cylindrical base paper is heat-bonded at its side and bottom end portions so that a cylindrical structure with a closed bottom end is formed for a cylindrical separator. This method does not require any change of moving direction of the base paper
21
from the cutting step to the winding step and, consequently, the production can be enhanced.
However, in the production method of
FIG. 3
in which the base paper
21
is rotated in the horizontal direction and pulled in the longitudinal direction to be cut and then rotated in the horizontal direction, an axial direction of the separator
4
is coincided with a width direction of the base plate
21
of the roll
20
and, therefore, the cylindrically formed separator is likely to be deformed when the end
4
A (
FIG. 1
) of the separator
4
is pressed radially inwardly by pushing the end
4
A by the gasket
9
of the closure body
6
. If such deformation is generated, the gel like zinc anode active mass
5
is moved into the cathode active mass
3
through a gap between the separator
4
and the gasket
9
when a shock or vibration is added to the alkaline cell
1
, resulting in generation of short circuits.
An example of the production method of the separator shown and described with reference to
FIG. 3
will be described more specifically with reference to
FIGS. 4A
,
4
B,
4
C and
4
D. In
FIG. 4A
, a base paper
21
in the form of a roll
20
is cut into a predetermined dimension and the cut base paper
21
is wound to form a cylindrical body
22
and then directed to a bottom forming step by a suitable feeding device (not shown) and one end of the cylindrical body is subject to a heat bonding to provide a closed bottom end.
In order to provide a reliable sealing effect of the closed bottom end, the end portion of the cylindrical body is bent prior to the heat bonding. Namely, as shown in
FIG. 4B
, a shaft
25
is inserted through the cylindrical body
22
and a blade-like die
24
is pressed downward against the upper end of the cylindrical body
22
to form a depression
22
b
as shown in
FIG. 4C
, and then a heat curl die
29
is pressed against the depressed upper end of the cylindrical body
22
as shown in
FIG. 4D
so that a semispherical end
22
a
is formed as illustrated in FIG.
4
E. Thus, the conventional separator
4
was obtained.
However, there are some inconveniences and difficulties in the conventional production method of the separator.
First, the cylindrical body
22
must be fed to a predetermined position by means of a feeder and, therefore, it is likely that the opening end portion of the cylindrical body
22
is accidentally deformed or collapsed during the feeding transporting operation due to some mechanical factors and/or shocks applied to the cylindrical body
22
, resulting in serious reduction of productivity.
Second, when a depression
22
b
is formed on top of the cylindrical body
22
, it depends largely upon the physical properties, as hardness, of the cylindrical body
22
and there are cases that it is difficult to form a desirable depression and, therefore, a sealing (blocking) property of the closed bottom end
22
b
is not complete or satisfactory. If a depression
22
b
is forcibly formed by adjusting the time and pressure of the blade-like die
24
against the top end of the cylindrical body
22
, it sometimes results in damages of the cylindrical body and reduction of productivity. Thus, a care must be taken to select definitely the material for the base paper for the separator but this is troublesome and requires additional time and labor.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a new separator for an alkaline cell, which can prevent any deformation to an end of the separator and also prevent short circuit within the cell structure when a shock or any other external force is added to the cell.
Another object of the present invention is to provide a new method of producing a separator for a battery or a cell such as an alkaline cell which permits reliability in sealing properties of the bottom end portion and high productivity of the separator.
In order to satisfy the first object of the invention, there is provided a separator for an alkaline cell, wherein the cell has a cylindrical cathode metal casing, a cathode mix mounted within the cathode metal casing, a separator which is formed by rotating a roll of a separator base paper
21
to be pulled out and cut to a predetermined length and then the separator base plate is rotated in the horizontal direction to form a cylindrical structure, an electrolyte dipped into the separator and the cathode mix, an anode active
Murakami Shuji
Ota Hirohiko
Tsutsui Kiyohide
Yamashita Katsuhiro
Crowell & Moring , L.L.P.
FDK Corporation
Sorkin David
Walker W. L.
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