Electricity: circuit makers and breakers – Multiple circuit control – Sequential operations
Reexamination Certificate
2003-07-01
2004-10-26
Friedhofer, Michael A. (Department: 2832)
Electricity: circuit makers and breakers
Multiple circuit control
Sequential operations
C200S406000, C200S341000
Reexamination Certificate
active
06809272
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a double action push switch incorporated in cameras or electronic devices such as mobile phones. More particularly, it relates to a double action push switch used as the shutter release button of a mobile camera phone.
2. Description of the Related Art
FIG. 13
to
FIG. 19B
illustrate one known double action push switch.
A plate member
240
is accommodated in a cavity
201
formed in a housing
200
. First, second, and third terminals
210
,
220
,
230
are fixed on the bottom plate of the housing
200
, and their respective connecting portions
212
,
222
,
232
are protruded outside of the housing
200
.
The open end of the cavity
201
is closed by a cover
250
, which has a hole
251
at its center, through which an operating portion of a key top
260
protrudes to the outside. The cover
250
is fixed to the housing
200
by locking springs
252
formed on a side face of the cover
250
, which engage with locking protrusions
203
protruded on an outer face of the housing
200
.
As shown in
FIGS. 19A and 19B
, the plate member
240
consists of a domed center contact portion
241
, an annular portion
244
around the center contact portion
241
separated therefrom by a pair of semi-circular arc holes
242
but continued therewith by a pair of coupling portions
243
, and parallel rectangular plate-like peripheral contact portions
245
opposite each other on the outer periphery of the annular portion
244
. The annular portion
244
is slanted downward from inside to outside and formed with wrinkles
246
at circumferentially equally spaced locations, each being offset by 90°.
The plate member
240
is initially in a resiliently deformed state inside the cavity
201
as it is held between an inner bottom face of the housing
200
and a lower face of the key top
260
, as shown in FIG.
16
and FIG.
17
. Its peripheral contact portions
245
are in contact with the contact points
211
of the first terminal
210
.
When the key top
260
is pushed down, its pressing protrusion presses the center contact portion
241
of the plate member
240
, inverting the annular portion
244
. This first deformation causes the periphery of the center contact portion
241
to touch the contact points
221
of the second terminal
220
, thereby establishing an electrical connection between the first and second terminals
210
,
220
.
When the key top
260
is pushed further down, its pressing protrusion presses the center contact portion
241
of the plate member
240
to cause further deformation. This second deformation causes the center of the center contact portion
241
to touch the contact point
231
of the third terminal
230
, thereby establishing electrical connection between the first, second, and third terminals
210
,
220
,
230
.
Since the prior art shown in
FIG. 13
to
FIG. 19B
performs the two step connection with one plate member
240
, the coupling portions
243
of the plate member
240
are subjected to too much stress, because of which the plate member
240
tends to break with fewer number of operation cycles.
Because the first deformation of the plate member
240
causes an inversion of the annular portion
244
which is formed by a bending process, and the second deformation causes inversion of the center contact portion
241
which is formed by a drawing process, stress is concentrated on the coupling portions
243
, which connect the annular portion
244
and center contact portion
241
. The coupling portions
243
are therefore particularly susceptible to cracks.
Another problem with the two step connection with one plate member
240
was that there was little freedom in setting different load characteristics for the first connection and the second connection.
That is, if the switch is designed to have desired load characteristics in the action of the first connection, then it inevitably has limitations in providing desired load characteristics for the action of the second connection.
The present inventors have designed a double action push switch as shown in Japanese Patent Application No. 2002-186830 that can resolve the above problems;
FIG. 20
to
FIG. 27C
illustrate this push switch.
The housing
300
is formed with a cavity
301
, and first, second, and third terminals
310
,
320
,
330
are fixed in the housing
300
. Their respective contact points
311
,
321
,
331
are exposed in the inner bottom face of the cavity
301
on the outer side, inner side, and at the center, and their respective connecting portions
312
,
322
,
332
are protruded outside of the housing
300
.
The open end of the cavity
301
is closed by a cover
340
, which has a hole
341
at its center, through which an operating portion of a key top
350
protrudes to the outside. The cover
340
is fixed to the housing
300
by locking springs
342
formed on a side face of the cover
340
engaging with locking protrusion
303
protruded on an outer face of the housing
300
.
The plate member accommodated inside the cavity
301
consists of first and second plates
360
,
370
spaced apart in the up and down direction.
As shown in
FIG. 25
to
FIG. 27C
, the first plate
360
is made up of a rectangular plate-like center contact portion
361
, an annular portion
364
around the center contact portion
361
spaced away therefrom by a pair of semi-circular holes
362
and linked thereto by strips of coupling portions
363
, and a pair of peripheral contact portions
365
on the outer periphery of the annular portion
364
at opposite locations. The center contact portion
361
has a downward protrusion
366
at its center and reinforcing upright portions
367
along the end edges of lengthwise direction. The annular portion
364
is formed with wrinkles
368
at circumferentially equally spaced locations.
The second plate
370
consists of two superposed pieces placed inside the cavity
301
as shown in
FIGS. 22A and 22B
, and has a dome-like shape protruding upwards.
When the key top
350
is pushed down, its pressing portion presses the center contact portion
361
of the first plate
360
, inverting the coupling portions
363
as well as causing resilient deformation of the annular portion
364
. This first deformation causes the protrusion
366
on the first plate
360
to touch the center of the second plate
370
, whereby electrical connection is established between the first and second terminals
310
,
320
.
When the key top
350
is pushed further down, the protrusion
366
on the first plate
360
presses the center of the second plate
370
and causes it to invert. This second deformation causes the center of the second plate
370
to touch the contact point
331
of the third terminal
330
, whereby electrical connection is achieved between the first, second, and third terminals
310
,
320
,
330
.
Because the plate member consists of two plates
360
,
370
, both of them are not subjected to excessive stress. The plate member therefore has a longer life than the prior art with a single plate member. Also, this double action push switch can have a wider range of variations in its load characteristics because it has more freedom in designing the switch to attain desired load characteristics for each of the first and second switching actions.
The construction shown in
FIG. 20
to
FIG. 27C
, however, has a problem that it occupies a relatively large mounting area on a printed circuit board because of large outer dimensions of the first plate
360
.
More specifically, when the annular portion
364
of the first plate
360
has an outer diameter of 5.5 mm, and the second plate
370
has an outer diameter of 2.3 mm, the housing
300
has outer dimensions of 7.8 mm×5.7 mm, measured in the top plan view of FIG.
20
.
The prior art shown in
FIG. 13
to
FIG. 19B
also has the problem of large mounting area on a printed circuit board because of large outer dimensions of the plate member
240
which performs the two step connecting action.
SUMMARY OF THE INVENTION
The pr
Friedhofer Michael A.
SMK Corporation
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