Electricity: circuit makers and breakers – Solid contact – Push button operated
Reexamination Certificate
2000-05-04
2001-08-07
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Solid contact
Push button operated
C200S406000, C200S341000, C200S01600R
Reexamination Certificate
active
06271491
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the structure of a push button switch used as a manipulating switch for various kinds of electronic equipment, and more particularly, to the structure of a dome-shaped movable contact having a reverse function.
2. Description of the Related Art
There are structures as shown in
FIG. 5
to
FIG. 7
as the structures of conventional push button switches.
FIG. 5
is a sectional view of a housing type push button switch,
FIG. 6
is a partially detailed view of a state in which a movable contact is in contact with a fixed contact, and
FIG. 7
is a partially detailed view showing the movable contact and the fixed contacts of a sheet type push button switch.
In
FIGS. 5 and 6
, a housing
21
is formed of a molded material of a synthetic resin or the like in a box-shape with an upper surface opened, and fixed contacts
22
and
23
, which are formed of a conductive metal such as brass or the like, are disposed on the inner bottom thereof. The fixed contacts
22
and
23
are buried in the housing
21
by a method of insert molding or the like, and connecting terminal
24
and
25
, which extend externally of the housing
21
, are formed at the other end sides of the fixed contacts
22
and
23
.
A movable contact
26
is formed of a spring member such as stainless steel, phosphor bronze or the like in a reversible dome-shape, and the lower peripheral edge of the movable contact
26
is placed in the housing
21
in contact with one of the fixed contacts, that is, the fixed contact
22
disposed on the inner bottom of the housing
21
. Further, the apex portion of the movable contact
26
is disposed in confrontation with the other fixed contact
23
with a predetermined interval therebetween, and a cylindrical projection
26
a
, which is formed in a cylindrical shape and projects upward, is disposed at the apex portion of the movable contact
26
. The cylindrical projection
26
a
is formed integrally with the movable contact
26
with its bottom
26
b
facing upward and its peripheral edge
26
c
facing downward.
A stem
27
is formed of a molded material of a synthetic resin or the like and includes a press section
27
a
for pressing the dome-shaped apex portion of the movable contact
26
, a locking section
27
b
locked to a cover
28
composed of a metal sheet and covering the opening of the housing
21
and a manipulating section
27
c
to be manipulated with a finger of an operator from the outside.
The operation of the above push button switch will be described. When the manipulating section
27
c
of the stem
27
is pressed and the stem
27
is pushed down thereby, the press section
27
a
presses the cylindrical projection
26
a
disposed at the apex portion of the movable contact
26
to thereby reverse the movable contact
26
, so that the cylindrical projection
26
a
disposed at the apex portion comes into contact with the fixed contact
23
. As a result, the fixed contact
22
is connected to the fixed contact
23
through the movable contact
26
.
In this case, since the cylindrical projection
26
a
, which is formed in the cylindrical shape and projects upward, is disposed at the apex portion of the movable contact
26
and the peripheral edge
26
c
of the cylindrical projection
26
a
is in contact with the fixed contact
23
, they are in contact with each other at a position from which dust
34
, which tends to gather at the center
23
a
of the fixed contact
23
, is avoided. Accordingly, the contact is stably performed and the reliability of the contact is enhanced as compared with the structure in which the apex portion is in direct contact with the center
23
a
of the fixed contact
23
.
FIG. 7
shows a case in which the movable contact
26
is used in a sheet type push button switch. In the figure, a circuit board
28
is composed of an insulating laminated sheet formed of a phenol resin or the like, and fixed contacts
29
and
30
, which are composed of an etched copper foil or the like, are disposed on the circuit board
28
. The movable contact
26
is disposed on the fixed contacts
29
and
30
, and the movable contact
26
is covered with a sheet member
31
formed of PET (polyethylene terephthalate) or the like. A spacer
32
is formed of an insulating material such as PET (polyethylene terephthalate) or the like in a sheet-shape and clamped between the circuit board
28
and the sheet member
31
, thereby forming an accommodating section
32
a
in which the movable contact
26
is accommodated. Note that, although not shown, a plurality of the fixed contacts
29
and
30
and the movable contacts
26
are disposed on the circuit board
28
.
While the above sheet type push button switch may be directly manipulated with a finger of an operator from above the sheet member
31
, another stem (not shown) or the like may be disposed on the sheet member
31
and the push button switch may be manipulated through the stem.
However, in the structure of the movable contact
26
of the above conventional push button switch, the cylindrical projection
26
a
which projects upward is disposed at the apex portion of the dome-shaped movable contact
26
and is integrally coupled with the movable contact
26
with the bottom
26
b
thereof facing upward and the peripheral edge
26
c
thereof facing downward. Accordingly, since the interior of the movable contact
26
surrounded by the cylindrical projection
26
a
acts as a non-movable region when it is reversed, there is a problem that feeling in manipulation is adversely affected when the push button switch is manipulated.
Further, in the sheet type push button switch, since a gap
33
is made between the peripheral portion of the cylindrical projection
26
a
and the sheet member
31
by the existence of the cylindrical projection
26
a
which projects upward of the movable contact
26
, an intimate contact property is bad and a problem resides in the reliability and outside appearance of a product.
Therefore, an object of the present invention is to solve the above problems and to provide the structure of a dome-shaped movable contact having a reverse function used in a push button switch, wherein it is possible that the movable contact comes into contact with a fixed contact at position excluding the central portion thereof where dusts is liable to gather, obtains high contact reliability, has good feeling in manipulation and is excellent in an intimate contact property with a sheet member covering the movable contact.
SUMMARY OF THE INVENTION
To solve the above problems, a first means of the present invention includes fixed contacts, a dome-shaped movable contact disposed above the fixed contacts, and a projection formed on the inner surface of the movable contact at a portion excluding a dome-shaped apex portion so as to be in contact with and separated from one of the fixed contacts.
A second means includes a housing, fixed contacts disposed on the inner bottom of the housing, a dome-shaped movable contact disposed above the fixed contacts, a stem movably disposed to the housing, and a projection formed on the inner surface of the movable contact at the portion excluding the dome-shaped apex portion so as to be in contact with and separated from one of the fixed contacts.
A third means includes a circuit board, fixed contacts disposed on the circuit board, a dome-shaped movable contact disposed above the fixed contacts, a sheet member adhered on the circuit board, and a projection formed on the inner surface of the movable contact at the portion excluding the dome-shaped apex portion so as to be in contact with and separated from one of the fixed contacts, wherein the movable contact is covered with the sheet member.
As a fourth means, a plurality of the projections are disposed on a dome-shaped inner surface in a scattered state.
Further, as a fifth means, the plurality of projections are disposed on an annular line.
REFERENCES:
patent: 4029916 (1977-06-01), Chu
patent: 4194105 (1980-03-01), Hodges
patent: 4207448
Iwama Naoya
Ono Yutaka
Yamagata Takeo
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Friedhofer Michael
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