Chemistry: electrical current producing apparatus – product – and – Current producing cell – elements – subcombinations and... – Cell enclosure structure – e.g. – housing – casing – container,...
Reexamination Certificate
1999-04-08
2001-05-08
Shaw, Clifford C. (Department: 1725)
Chemistry: electrical current producing apparatus, product, and
Current producing cell, elements, subcombinations and...
Cell enclosure structure, e.g., housing, casing, container,...
C429S171000, C429S172000, C029S623100, C029S623200
Reexamination Certificate
active
06228530
ABSTRACT:
BACKGROUND
The present invention relates to a dry cell which is relatively small in size and has a cylindrical appearance and to a method of manufacturing an outer metal jacket of the dry cell.
Since the material for outer jackets of a small cylindrical dry cell was changed from paper to metal, its ability to prevent leakage has been improved thus increasing the performance of the dry cell. Such a metallic outer jacket of a dry cell (referred to as simply an outer metal jacket) is commonly fabricated in such a producing process as shown in FIG.
6
. The procedure starts with cutting a hoop material of about 0.2 mm thickness made of tin-plated steel into rectangular base sheets
1
of predetermined dimensions, for example 785 mm wide and 850 mm long, as shown in FIG.
6
(
a
). This is followed by slitting and trimming two edges of about 2 mm width along both opposing sides of the base sheet
1
. After removing the two edge pieces
2
, slits are formed which are equally spaced and parallel to the sides of the base sheet
1
as denoted by the two-dot chain lines in FIG.
6
(
b
). The base sheet
1
is then cut along these slits into a group of intermediate strips
3
as shown in FIG.
6
(
c
). Each intermediate strip
3
is punched out with a blanking die as shown in FIG.
6
(
d
), thus producing a number of metal jacket blanks
4
, one of which is shown in FIG.
6
(
e
).
The metal jacket blank
4
is then rolled to a cylindrical shape as shown in FIG.
6
(
f
). While two side edges
4
a
and
4
b
of the blank
4
are adjoined to each other, a base
4
c
is inwardly crimped to form a bottom
5
, thus making a cylindrical outer metal jacket
7
with a bottom. The outer metal jacket
7
is loaded through the open end thereof with a cell member which comprises a power generating element filled in a zinc can and is coated with an insulating tube. The upper end
4
d
of the outer metal jacket
7
is then inwardly crimped to be pressed via an insulating ring against the shoulder of the cell member, thus producing a small cylindrical dry cell
8
as shown in FIG.
5
.
The rectangular blank
4
punched out from the intermediate strip
3
has notches
9
a
,
9
b
at four corners thereof formed by removing triangular segments as shown in FIG.
6
(
e
). When the blank
4
is rolled and its base
4
c
is crimped inwardly or its upper end
4
d
is crimped inwardly with the cell member loaded therein, each pair of notches
9
a
or
9
b,
at the upper or lower side are adjoined to each other along a joint
10
between the two side edges
4
a
and
4
b
or in the radial direction R of the outer metal jacket
7
, forming a curled abutment joint
11
as shown in FIG.
5
.
More specifically, for forming the curled abutment joint
11
, the periphery of the outer metal jacket
7
at its upper end is pressed into a specific semicylindrical curling mold which has a curved cross section. As the upper end of the outer metal jacket
7
is gradually bent to form an even curve all around its periphery, the opposing notches
9
a
are steadily adjoined to each other from the outer side to the inner side. When the notches
9
a
are bent to abut each other, a considerable amount of stress is locally exerted along the curled abutment joint
11
and the bending stress is concentrated thereon thus causing buckling.
Further, the cell member loaded in the outer metal jacket
7
varies in height. If the cell member is short, an extra stress is given after the two notches
9
a
are attached to each other to form the curled abutment joint
11
. Such locally concentrated bending stress causes dents
12
on either side of the abutment joint as shown in
FIG. 5
, which damage the appearance of the outer metal jacket
7
. Also, the two notches
9
a
are fixedly pressed against each other along the curled abutment joint
11
, thus firmly pressing a seal member of the cell, which may obstruct the discharge of a gas from the cell in case the gas pressure inside the cell
8
soars unexpectedly.
In order buckling, an improved cylindrical dry cell has been proposed in which four corners of an outer metal jacket blank at upper and lower ends of both sides are rounded off by removing segments of different lengths or heights which are determined in a specific ratio (as disclosed in Japanese Utility-model Publication No. 1-19053). However, it is necessary to cut the blank of the cylindrical dry cell to a desired shape under precise control of the blanking operation. Especially for producing dry cells of small size, it is difficult to precisely control the configuration of tiny blanks when punching them out. On the other hand, the outer metal jacket for dry cells of larger size is jointed by laser welding, whereby the buckling is prevented. However, laser welding is generally not utilized for producing small dry cells because of its low productivity and high producing cost.
In order to form the small notches
9
a
,
9
b
having a desired configuration at four corners of the metal jacket blanks
4
in the production process of the outer metal jacket
7
described above, there is virtually no alternative but to punch out a plurality of blanks
4
from the rectangular intermediate strip
3
which is slightly greater in width than a pair of blanks
4
arranged side by side as shown in FIG.
6
(
d
). When the dry cell is large in overall size, the notches may be provided by cutting off four corners of a rectangular strip. However, the notches
9
a
,
9
b
of the blank
4
for smaller dry cells are normally minute, i.e., have a height h of 2.2 mm along the sides
4
a
and
4
b
and a width d of 0.35 mm from the sides
4
a
and
4
b.
The cutting tool of the cutting machine for providing such minute notches
9
a
,
9
b
must be extremely sharp and has a short life. Moreover, it is impossible in practice to securely hold a tiny metal jacket blank
4
precisely at a given position.
Accordingly, a waste of material is left in a large amount after the intermediate strip
3
is punched out as can be seen from FIG.
6
(
d
). The number of the blanks
4
punched out from the intermediate strip
3
is limited thus being inefficient in production. In light of the mass production of small dry cells in recent years, such method as described above which creates the loss of material is unfavorable from the economical point of view.
It is thus an object of the present invention to provide a dry cell having such a configuration that any dents caused by the buckling when crimped is effectively prevented, and a method of producing the outer metal jackets efficiently.
SUMMARY OF THE INVENTION
In order to solve the above described problems, a dry cell of the present invention is comprised of a cylindrical cell member and an outer metal jacket for encasing the cell member, the metal jacket being formed by rolling a metal jacket blank of a rectangular metal strip into a cylindrical shape to cause the opposing side edges thereof to abut each other and by inwardly curling and crimping a lower end of the blank to make a bottom, the cell member being sealed in the metal jacket by inwardly curling and crimping an upper end of the metal jacket. The metal jacket blank is provided with notches at both corners of one side edge thereof where the abutment joint is formed, and the notches are respectively adjoined to an upper end and a lower end of the other side edge of the blank, forming a curled abutment joint along a direction which is different from the radial direction of the metal jacket.
The blank for the metal jacket has notches at the upper and lower ends of only one side thereof. Thus, the upper and lower notches come into direct contact with their corresponding edges of the other side at the very end of the curling action. As the notches come to join with the other end to form the curled abutment joint at the very end of the curling action, the bending stress is not concentrated locally to the curled abutment joint, thus creating no dents caused by the buckling.
It is preferable that the width of the notches at one side edge of the metal jacket blank is determ
Dokyu Tensaburo
Ogino Keiji
Sakamoto Akio
Cooke Colleen P.
Jordan and Hamburg LLP
Matsushita Electric - Industrial Co., Ltd.
Shaw Clifford C.
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