Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Separator – retainer or spacer insulating structure
Reexamination Certificate
2000-11-30
2003-04-01
Ryan, Patrick (Department: 1745)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Separator, retainer or spacer insulating structure
C429S129000, C429S140000, C429S145000, C429S133000, C429S247000, C029S623100
Reexamination Certificate
active
06541152
ABSTRACT:
TECHNICAL FIELD
The present invention related to a cylindrical battery wherein discharge performance and reliability are enhanced by improving the mounting structure of the separator that seperates the positive electrode material and negative electrode material within the battery, and a method and device for manufacturing such a cylindrical battery.
BACKGROUND ART
FIG. 9
is a partially sectioned front view showing a prior art construction of an alkaline dry battery
30
as one example of a cylindrical battery. A battery casing
1
of cylindrical shape having a bottom is integrally provided with a positive electrode projection
6
constituting the positive electrode terminal of the battery, in the middle of its bottom face. This battery casing
1
accommodates positive electrode mixture pellets
2
and a negative electrode gel
4
in the interior thereof, with a tubular separator
35
interposed therebetween. The open end of battery casing
1
is sealed by a sealing plate
7
made of resin, a negative electrode terminal
8
connected to a negative electrode current collector
9
being mounted on this sealing plate
7
. Tubular separator
35
is formed in cylindrical shape by winding separator paper into a roll, a portion at the bottom end thereof being folded inwards contacting the bottom face of the battery casing
1
and constituting a bottom part
35
a.
Since the middle portion of this bottom part
35
a
is open, a circular bottom separator
36
having a larger diameter than the internal diameter of tubular separator
35
is inserted within tubular separator
35
in order to cover this aperture portion and thereby prevent internal short circuits between negative electrode gel
4
and battery casing
1
. Furthermore, a step
1
a
is provided in the bottom face of battery casing
1
, to absorb even if only to a small extent, the thickness of the bottom part
35
a
of tubular separator
35
and bottom separator
36
, so as to avoid, as far as possible, offset in the vertical direction of the reaction surfaces where the negative electrode gel
4
and positive electrode mixture pellets
2
face each other.
The mounting of tubular separator
35
and bottom separator
36
in the manufacturing step of this alkaline dry battery
30
is performed by a manufacturing device shown in
FIGS. 10A-10D
.
In
FIG. 10A
, a battery feed jig
15
holding a battery casing
1
is moved directly below a winding rod
33
of a tubular separator installation device
32
, after positive electrode mixture pellets
2
have been accommodated in battery casing
1
in a previous step, not shown. The diameter of winding rod
33
below step
38
is formed smaller than the diameter thereabove by an amount corresponding to the thickness of tubular separator
35
, and this winding rod is supported such as to be rotated in the forwards and reverse directions and can be raised and lowered. When separator paper, that has been cut to prescribed dimensions, is supplied to the gap between winding rod
33
and winding guides
34
, winding rod
33
is rotated in the forwards direction, and the separator paper is wound about the portion of winding rod
33
lower than step
38
. In this process, slackness in winding is avoided by pressing the separator paper on to winding rod
33
by means of winding rollers
37
. In this way, a tubular separator
35
is formed on winding rod
33
as shown, by winding the separator paper about winding rod
33
a prescribed number of times.
Next, as shown in
FIG. 10B
, winding rollers
37
are retracted from winding rod
33
, winding rod
33
is lowered, and battery feed jig
15
is raised, so that winding rod
33
with tubular separator
35
wound thereon is inserted into battery casing
1
. At this point the tubular separator
35
, when inserted into battery casing
1
, is released from the restraint applied by winding guides
34
, so it increases its winding radius by springing back of its own accord so that it is in tight contact with positive electrode mixture pellets
2
. Since the tip of tubular separator
35
is wound in a hollow condition with no winding rod
33
at its center, tubular separator
35
is pressed by step
38
and thereby inserted into battery casing
1
; furthermore, when it is pressed against the bottom face of battery casing
1
, this tip is squeezed inwards. Then, by further pressure applied by the tip of winding rod
33
, the bending produced by this squeezing is molded into a flat condition, forming bottom part
35
a
(see FIG.
9
). After this, winding rod
33
is released from tubular separator
35
by backwards rotation and raised, while battery feed jig
15
is lowered, so that tubular separator
35
is left in a condition in which it is installed in battery casing
1
.
Battery casing
1
with tubular separator
35
installed therein is then fed to the next step by battery feed jig
15
and, as shown in
FIG. 10C
, is moved below bottom separator installation device
39
. Bottom separator installation device
39
is provided with an insertion rod
40
and insertion guide hole
41
; when bottom separator
36
that has been cut to circular shape is supplied to above insertion guide hole
41
, insertion rod
40
is lowered. Simultaneously, battery feed jig
15
is raised and the open end of battery casing
1
is brought into contact with a locating element
42
of bottom separator installation device
39
. Since insertion guide hole
41
is formed of cylindrical shape of smaller diameter than the diameter of bottom separator
36
, when bottom separator
36
is inserted into insertion guide hole
41
by insertion rod
40
, the circumferential region of bottom separator
36
is raised, forming a flat-bottomed U-shape in cross-section. When insertion rod
40
is further lowered, as shown in
FIG. 10D
, bottom separator
36
is installed on bottom part
35
a
produced by squeezing in of the bottom end of tubular separator
35
.
After undergoing the steps of insertion of tubular separator
35
and bottom separator
36
, battery casing
1
is fed to the subsequent steps (not shown) to complete the alkaline dry battery
30
.
However, the battery construction and its manufacturing steps in the prior art described above were subject to the following problems.
(1) The bottom end part of tubular separator
35
was squeezed inwards to form bottom part
35
a
and further, in order to block the aperture produced in the middle of bottom part
35
a,
this aperture portion was closed by placing on bottom part
35
a
a bottom separator
36
. Because of this, since a double-layer structure is adopted in which, in addition to the folding-over produced by squeezing of the bottom part
35
a,
bottom separator
36
is overlaid thereon, the thickness of the separator portion is increased, resulting in the production of a step (offset in the axial direction) in the reaction surfaces of negative electrode gel
4
and positive electrode mixture pellets
2
that face each other through tubular separator
35
. Even though, as described above, a step
1
a
is provided in the bottom face of battery casing
1
, this is still insufficient to eliminate the step previously referred to. Furthermore, the discharge performance of the battery is lowered due to the diminution in capacity to receive the negative electrode gel.
(2) In addition to the overlapping in pleated form of the bottom part
35
a
produced by the squeezing of the bottom end part of tubular separator
35
, due to the double-layer construction with bottom separator
36
, a construction is produced in which the separator portion at the bottom of battery casing
1
is resistant to deformation. As a result, if the negative electrode gel
4
is caused to expand by over-discharging, since this expansion force cannot escape at the bottom, the internal pressure produced by the expansion acts on the sealing plate
7
, risking failure of the thin part
7
a
provided in sealing plate
7
. The purpose of the provision of this thin part
7
a
is, in the first place, to prevent bursting of the battery if the internal pressure rises abnorma
Aoi Takayuki
Koda Minoru
Moriwaki Tsutomu
Nakatsuka Saburo
Noya Shigeto
Jordan and Hamburg LLP
Martin Angela J.
LandOfFree
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