Seal for a joint or juncture – Seal between fixed parts or static contact against... – Contact seal for other than internal combustion engine – or...
Reexamination Certificate
1999-06-09
2003-10-21
Knight, Anthony (Department: 3676)
Seal for a joint or juncture
Seal between fixed parts or static contact against...
Contact seal for other than internal combustion engine, or...
C277S650000, C277S924000, C429S006000, C429S185000
Reexamination Certificate
active
06634649
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cracking-resistant gasket having a function to stably prevent an explosion, a method of molding the gasket, and a cylindrical alkaline-manganese dioxide cell incorporating the gasket to provide an excellent leakage-proof structure.
2. Description of Related Art
If a cylindrical alkaline-manganese dioxide cell is overcharged or over-discharge due to an incorrect use, gases are generated furiously inside the container or can of the cell to elevate the internal pressure, possibly resulting in a leakage of the electrolyte, etc. and in an explosion in some cases. To avoid this, the cylindrical alkaline-manganese dioxide cell is provided with an explosion-proof mechanism to quickly purge gases having been generated inside the cell and elevated the internal pressure.
Generally, the above-mentioned explosion-proof mechanism adopted in the conventional alkaline-manganese dioxide cells is a thinned portion of a gasket sealing the opening of the cell can and which acts as an explosion-proof safety valve. More specifically, a stress caused by an internal pressure elevated by gases generated inside the cylindrical alkaline-manganese dioxide cell is concentrated to the gasket whose thinnest portion will be torn. The gases generated inside the cell are purged to outside through an opening thus formed in the gasket, thereby preventing the cell from exploding due to an elevated internal pressure inside the cell.
There have so far been proposed various types of conventional gaskets formed in various shapes, by molding, from a synthetic rein such as Nylon, polypropylene, etc. or a rubber as shown in
FIGS. 1
to
4
.
FIG. 1
illustrates a first example of conventional gasket in the form of an axial sectional view. The gasket is generally indicated with a reference numeral
50
. It consists of a thick-walled cylindrical portion
51
formed at the center thereof and having a convex axial-section (will be referred to as “hob portion” hereinunder), a disc-like portion
52
formed along the outer circumference of the hob portion
51
and concentrically with he hob portion
51
(will be referred to as “diaphragm portion” hereinunder), thin portions
53
formed between the hob and diaphragm portions
51
and
52
and in a position nearer to the upper side of the diaphragm portion
52
, and a peripheral portion
54
formed contiguously along the outer circumference of the diaphragm portion
52
to have the axial-sectional shape of a curve. The hob portion
51
is a cylinder having a hob hole
55
open at the top thereof as indicated with a reference numeral
55
a
and at the bottom thereof as indicated with a reference numeral
55
b
and whose inside diameter is gradually increased downward so that the lower opening
55
b
of the hob hole
55
is larger than the upper opening
55
a
. The thin portions
53
are two arcs each formed concentrically with the hob portion
51
as shown in FIG.
5
.
FIG. 2
shows a second example of conventional gasket in the form of an axial sectional view. This gasket is generally indicated with a reference numeral
60
. It consists of a hob portion
61
, diaphragm portion
62
, thin portions
63
and a peripheral portion
64
as in the gasket
50
having been described above. In this example, the hob portion
61
is a cylinder having a hob hole
65
whose lower portion is larger in diameter than the upper portion. That is to say, the wall of the hob hole
65
is stepped at the boundary between the upper and lower portions. As shown in
FIG. 5
, the thin portions
63
are two arcs concentric with the hob portion
61
similarly to the thin portions
53
of the gasket
50
.
FIG. 3
is an axial sectional view of a third example of conventional gasket. The gasket is generally indicated with a reference numeral
70
. The gasket
70
consists of a hob portion
71
formed to have a convex section, a diaphragm portion
72
formed concentrically with the hob portion
71
and obliquely towards the upper end portion of the hob portion
71
, thin portion
73
formed between the hob portion
71
and diaphragm portion
72
in a position nearer to the upper side of the diaphragm portion
72
, and a peripheral portion
74
formed contiguously along the outer circumference of the diaphragm portion
72
to have the axial-sectional shape of a curve. The hob portion
71
is formed longer than those
51
and
61
of the gaskets
50
and
60
, respectively, to project downward from the bottom surface of the diaphragm portion
72
. The hob portion
71
is a cylinder having a straight bob bole
75
having a same diameter everywhere through it. The thin portion
73
takes the form of a circle formed concentrically with the hob portion
71
as shown in FIG.
6
.
FIG. 4
shows a fourth example of conventional gasket in the form of an axial sectional view. The gasket is generally indicated with a reference numeral
80
. The gasket
80
includes a hob portion
81
, a diaphragm portion
82
formed concentrically with the bob portion
81
, a thin portion
83
formed in a portion of the diaphragm portion
82
, and a peripheral portion
84
formed contiguously along the outer circumference of the diaphragm portion
82
. The bob portion
81
consists of upper and lower halves projecting upward and downward, respectively, to a generally same extent from the diaphragm portion
82
a
. The bob portion
81
is a cylinder having formed therein a straight bob hole
85
open at the top thereof as indicated with a reference numeral
85
a
and at the bottom thereof as indicated with a reference numeral
85
b
and having a same diameter everywhere through it. The thin portion
83
is formed to extend in a round hole in a portion of the diaphragm portion
82
as shown in FIG.
7
.
The aforementioned gaskets
50
,
60
,
70
and
80
(will be generically called “gasket
50
” hereinunder) are formed by an injection molding in which a molten resin is injected from an injection gate into a space defined between male and female molds.
FIG. 8
is an axial sectional view of a first example of mold assembly for molding the conventional gaskets. The mold assembly is generally indicated with a reference numeral
90
. Referring to
FIG. 8
, how to mold the gasket using the mold assembly
90
will be described herebelow. The mold assembly
90
is a combination of a male mold
90
a
and a female mold
90
b
. When set in place, the male and female molds
90
a
and
90
b
define together a cylindrical space
91
for the hob portion, a flat space
92
for the diaphragm portion, a curved space
93
for the peripheral portion, and a narrower space
94
contiguous to the inner end of the flat space
92
to form the thin portion
94
. The female mold
90
b
has a pin point gate
96
formed therein in the proximity of the base of a core pin
95
. The pin point gate
96
is open at the bottom of the cylindrical space
91
. The gasket
50
is molded by injecting a molten resin into the mold assembly
90
.
FIG. 9
shows, in the form of an axial sectional view, a second example of mold assembly used for molding the conventional gaskets. The mold assembly is generally indicated with a reference numeral
100
. The mold assembly
100
is a combination of a male mold
100
a
and a female mold
100
b
. Different from the mold assembly
90
shown in
FIG. 8
, the mold assembly
100
is of a gate type for molding the gasket
50
. As in the gate
90
, the gate
100
has a cylindrical space
101
, a flat space
102
, a curved space
103
, and a narrower space
104
. By injecting a molten resin into the mold assembly
100
from a side gate
105
open at the end of the curved space
103
, the gasket
50
is molded.
The gate
50
can be formed using any one of various mold assemblies having so far been proposed and which are provided with a film gate or disc gate formed to extend from the bottom of the cylindrical space for the hob portion, a single- or multi-point pin gate formed to extend from the flat space for the diaphragm portion, and a submarine gate formed to
Hashimoto Kazuhiro
Morita Hiroyuki
Sugawara Akihiro
Tokugawa Hideaki
Yamaguchi Norishige
Bell Boyd & Lloyd LLC
Knight Anthony
Pickard Alison K.
Sony Corporation
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