Electricity: circuit makers and breakers – Solid contact – Membrane type
Reexamination Certificate
2000-05-01
2001-09-11
Friedhofer, Michael (Department: 2832)
Electricity: circuit makers and breakers
Solid contact
Membrane type
C200S517000, C200S344000
Reexamination Certificate
active
06288353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a computer keyswitch, and more particularly, to a computer keyswitch with accurately positioned rubber domes.
2. Description of the Prior Art
A computer keyswitch is a common input device. It comprises a base plate, a membrane circuit board installed on the base plate having a plurality of pressure sensors, a plurality of upwardly protruding rubber domes each on a pressure sensor of the membrane circuit board, and a plurality of keycaps each on a rubber dome. Each of the rubber domes is used to elastically support a corresponding keycap. When the keycap is depressed, the rubber dome will trigger the pressure sensor underneath to generate a key-pressing signal. There are two types of rubber domes. Rubber domes of the first type are monolithically formed on a rubber sheet. These rubber domes are automatically positioned on corresponding pressure sensors when the rubber sheet is placed on the membrane circuit board. Rubber domes of the second type are of a stand-alone type. They are individually positioned on the pressure sensors of the membrane circuit board. Nowadays, research is focused on reducing the thickness and weight of the keyswitch. Moreover, means for improving the positioning precision of the rubber domes on the pressure sensors is also strongly considered.
Please refer to
FIGS. 1 and 2
.
FIG. 1
is a component diagram of a keyswitch
13
of a computer keyswitch.
FIG. 2
is a cross-sectional view of the keyswitch
13
. The keyswitch comprises a base plate
12
, a membrane circuit board
14
installed on the base plate
12
, and a rubber sheet
20
positioned on the membrane circuit board
14
. The rubber sheet
20
has a plurality of upwardly protruding rubber domes
22
on its upper side
23
, and three penetrating holes
31
set up around each of the rubber domes
22
. The membrane circuit board
14
has a plurality of pressure sensors
16
for generating key-pressing signals and three penetrating holes
30
installed around each of the pressure sensors
16
. The base plate
12
has a plurality of holding legs
32
protruding upwardly through the penetrating holes
30
,
31
on the membrane circuit board
14
and the rubber sheet
20
. In order to reduce the thickness of the computer keyswitch, the thickness of the rubber sheet is often reduced, causing a weakened structure of straps
21
around each rubber dome
22
and thus distortions of the straps
21
. This will then generate position errors between the rubber domes
22
and the pressure sensors
16
.
Please refer to
FIGS. 3 and 4
.
FIG. 3
is a component diagram of a keyswitch
37
of another computer keyswitch.
FIG. 4
is a cross-sectional view of the keyswitch
37
. The computer keyswitch comprises a base plate
11
, a membrane circuit board
17
installed on the base plate
11
, a plurality of stand-alone rubber domes
23
installed on the membrane circuit board
17
, and a plastic frame board
34
installed on the membrane circuit board
17
for fixing positions of the rubber domes
23
. The membrane circuit board
17
has a plurality of pressure sensors
16
for generating key-pressing signals. The plastic frame board
34
has a plurality of penetrating holes
35
positioned corresponding to the pressure sensors
16
. When the plastic frame board
34
is installed on the membrane circuit board
17
, the rubber domes
23
on the pressure sensors
16
will penetrate through the penetrating holes
35
of the plastic frame board
34
, and edges
23
a
of the rubber domes
23
will be clamped between the plastic frame board
34
and the membrane circuit board
17
. Using the plastic frame board
34
to fix the positions of the rubber domes
23
has the drawback of increasing the thickness of the computer keyswitch.
SUMMARY OF THE INVENTION
It is therefore an objective of the present invention to provide a computer keyswitch with accurately positioned rubber domes and a reduced thickness to solve the above mentioned problems.
In a preferred embodiment, the present invention provides a computer keyswitch with accurately positioned rubber domes. The computer keyswitch includes a base plate, a membrane circuit board installed on the base plate having a plurality of pressure sensors and a plurality of penetrating holes installed around each of the pressure sensors, a rubber sheet positioned on the membrane circuit board having a plurality of upwardly protruding rubber domes on its upper side above the pressure sensors and a plurality of penetrating holes around each of the rubber domes, a plurality of keycaps, and a plurality of connecting devices each connected between a keycap and the base plate through the penetrating holes of the rubber sheet and the membrane circuit board. The membrane circuit board further includes a plurality of fastening holes installed among the pressure sensors, and the rubber sheet further includes a plurality of corresponding rubber pegs installed on its lower side for engaging the fastening holes of the membrane circuit board in order to accurately position the rubber domes of the rubber sheet on the pressure sensors of the membrane circuit board.
It is an advantage of the present invention that the rubber domes can be accurately positioned on the pressure sensors and the thickness of the computer keyswitch can be reduced.
These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment which is illustrated in the various figures and drawings.
REFERENCES:
patent: 5500497 (1996-03-01), Merriman
patent: 5850194 (1998-12-01), Lin
patent: 5950810 (1999-09-01), Pan et al.
patent: 5952629 (1999-09-01), Yoshinaga et al.
patent: 6040541 (2000-03-01), Li
patent: 6057522 (2000-05-01), Chao
Acer Communications and Multimedia Inc.
Friedhofer Michael
Hsu Winston
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