Key input device

Details Key input device Key input device

2000-07-24

2003-10-14

Chiang, Jack (Department: 2642)

Telephonic communications

Supervisory or control line signaling

Substation originated

C379S433070

Reexamination Certificate

active

06633641

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to key input devices for use in portable telephones and the like, and more particularly to a key input device comprising a plurality of manual keys including a seesaw key adapted to selectively close one of pairs of key contacts.
BACKGROUND OF THE INVENTION
With reference to
FIG. 8
, portable telephones usually have a casing
1
formed by a front case
11
and a rear case
12
. A display
13
and a plurality of manual keys
14
are arranged on the surface of the front case
11
. These manual keys
14
include a seesaw key
15
for use in selecting one of functions. The illustrated seesaw key
15
is adapted to selectively close one of four pairs of key contacts for the selection of the corresponding function.
The casing
1
has a circuit board
3
disposed in its interior as shown in FIG.
9
. Arranged on the circuit board
3
are a key sheet assembly
40
to be depressed by the manual keys
14
, the display
13
, a high-frequency circuit module
32
, a vibrator
2
comprising a motor
22
and an eccentric weight
21
attached to the output shaft of the motor for notifying the user of incoming calls, etc.
With reference to
FIG. 10
, the key sheet assembly
40
has a dome sheet
7
of PET disposed over a base plate
5
, with a spacer sheet
60
interposed therebetween, and having a plurality of upwardly bulging dome portions
75
. The manual keys including the seesaw key
15
are arranged above the dome sheet
7
for depressing the respective dome portions
75
. The spacer sheet
60
is formed with a plurality of circular holes
64
corresponding to the respective dome portions
75
and slotlike air vents
63
interconnecting these circular holes
64
as seen in FIG.
11
.
With the key sheet assembly
40
, the dome portion
75
is elastically restorably inverted by being depressed by the corresponding manual key to bring a contact terminal
52
provided on the inner surface of the dome portion
75
into contact with a contact electrode
51
provided on the surface of the base plate
5
to close a pair of contacts.
To reliably close the key contacts of the key sheet assembly
40
, the contact terminal
52
on the inner surface of the dome portion
75
of the dome sheet
7
must be brought into contact with the contact electrode
51
on the surface of the base plate
5
over as large an area as possible. It is therefore necessary to depress the dome portion
75
vertically downward.
However, in the case of the dome portions
75
to be depressed by the seesaw key
15
, a pusher
83
projecting downward from an end portion of the seesaw key
15
depresses the corresponding dome portion
75
in an oblique direction when the seesaw key
15
is moved. Stated more specifically with reference to
FIG. 10
, the pusher
83
of the seesaw key
15
exerts a depressing force F at an angle of &thgr; with a center axis V extending through the dome portion
75
perpendicular thereto, consequently deforming the dome portion
75
to a distorted form and bringing the contact terminal
52
on the inner surface of the dome portion
75
into point contact with the contact electrode
51
on the base plate
5
, hence the problem of failing to close the key contacts reliably.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a key input device which is adapted to close key contacts reliably even with a seesaw key.
The present invention provides a key input device which comprises a dome sheet
7
disposed over a base plate
5
and having a plurality of upwardly bulging dome portions
71
, and a plurality of manual keys
14
arranged above the dome sheet
7
for depressing the respective dome portions
71
, the manual keys
14
including a seesaw key
15
adapted to selectively depress one of dome portions
72
included among the dome portions
71
, each of the dome portions
71
being elastically restorably invertible by being depressed by the corresponding manual key
14
to bring a contact terminal
52
formed on an inner surface of the dome portion
71
into contact with a contact electrode
51
formed on a surface of the base plate
5
and close contacts.
The dome sheet
7
has a flat sheet portion
70
formed around the dome portions
71
and comprising an inner region
74
extending inwardly of the dome portions
72
to be selectively depressed by the seesaw key
15
, and an outer region
73
extending outwardly of the dome portion
72
, a spacer sheet
6
being interposed between the base plate
5
and the dome sheet
7
and being formed with a plurality of circular holes
61
corresponding to the respective dome portions
71
, the interposed spacer sheet
6
providing a difference in level from the surface of the base plate
5
between the inner region
74
of the flat sheet portion
70
of the dome sheet
7
and the outer region
73
thereof, the inner region
74
being positioned at a lower level than the outer region
73
.
Since the inner region
74
of the flat sheet portion of the dome sheet
7
is at a lower level than the outer region
73
thereof in the key input device of the present invention, each of the dome portions
72
to be selectively depressed by the seesaw key
15
is so inclined as to be positioned at a lower level toward the inner region
74
and at a higher level toward the outer region
73
. Thus, each dome portion
72
has its center axis inclined with respect to a perpendicular to the surface of the base plate
5
.
When one of these dome portions
72
is pushed by depressing the seesaw key
15
, the center axis C extending through the dome portion
72
perpendicular thereto is accordingly positioned in the same or approximately the same direction as the direction in which the depressing force F of the seesaw key
1
acts. As a result, the dome portion
72
is deformed symmetrically about the center axis, bringing the contact terminal
52
on the inner surface of the dome portion
72
into contact with the corresponding contact electrode
51
on the base plate
5
over a sufficient area. Since the dome portion
72
deforms symmetrically about the center axis, this portion
72
enables the user to feel the same sharp click as when with the other manual keys
14
are depressed.
According to a specific embodiment of the invention, the spacer sheet
6
has an opening
65
formed inwardly of circular holes
62
corresponding to the respective dome portions
72
to be selectively depressed by the seesaw key
15
and including the circular holes
62
, and the dome sheet
7
has its flat sheet portion
70
joined at the inner region
74
to the surface of the base plate
5
through the opening
65
. With this embodiment, a level difference in match with the thickness of the spacer sheet
6
is provided between the inner region
74
of the flat sheet portion
70
of the dome sheet
7
and the outer region
73
thereof.
With the key input device of the present invention, the seesaw key
15
, like the other keys, brings the contact terminal
52
on the inner surface of the dome portion
72
into contact with the corresponding contact electrode
51
on the base plate
5
over a sufficient area as described above, whereby the key contacts can be closed reliably.


REFERENCES:
patent: 4194105 (1980-03-01), Hodges
patent: 01-149329 (1989-06-01), None
patent: 3-13951 (1991-03-01), None
patent: 3-23639 (1991-05-01), None
patent: 4-60286 (1992-09-01), None
patent: 07-320588 (1995-12-01), None
patent: 07-320589 (1995-12-01), None

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