Electricity: circuit makers and breakers – Electric switch details – Actuators
Reexamination Certificate
2003-04-04
2004-01-27
Enad, Elvin (Department: 2832)
Electricity: circuit makers and breakers
Electric switch details
Actuators
C200S341000, C200S292000
Reexamination Certificate
active
06683264
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority from Japanese application serial no. 2002-102559, filed Apr. 4, 2002.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a key switch structure for use in computer keyboards. More particularly, the present invention pertains to a thin-form key switch structure that is suitable for use in thin notebook-type personal computers or other low profile computers.
2. Description of the Prior Art
With the advent and popularity of thin, lightweight notebook-type personal computers, manufacturers have continuously sought to further reduce the size, weight and thickness of such computers. The size, height and weight of the key switches that are positioned under each keytop contribute significantly to the size and weight of notebook computers. Thus, manufacturers have attempted to achieve such reductions by developing thin-forming or low profile key switches. However, there are several constraints that make further reduction of the height and weight of the key switch very difficult. For example, for optimal operability a minimum keystroke length of 2.6 to 2.7 is required as well as a certain click sensation. Under such constraints, any significant additional height or weight reduction of key switches cannot be achieved using the conventional switches.
The key switch disclosed in JP Patent 2001-14083 is an example of a key switch which retains a fixed keystroke and click sensation. The main portions of this key switch are as shown, for example, in the vertical cross sections depicted in
FIGS. 5 and 6
as well as in the stabilizer section of a conventional key switch as depicted in FIG.
7
.
FIG. 5
shows the key switch of Section A—A of
FIG. 7
in the OFF state.
FIG. 6
shows the same key switch but from a perspective of Section B—B of FIG.
7
and in the ON state.
Referring to the key switch of depicted in
FIG. 5
, the key switch structure is comprised of reinforcing base plate
1
, membrane switch
2
disposed on reinforcing base plate
1
, frame
3
on membrane switch
2
, stabilizer
4
, key top
5
, and click rubber
6
sandwiched between the membrane switch
2
surface and the key top
5
bottom surface. Membrane switch
2
includes two (flexible film) layers
8
and
9
. Membrane switch
2
further includes spacer
7
that is positioned between membrane layers
8
and
9
. Electrical contact
10
and electrical circuits are provided on the opposing surfaces of membrane layers
8
and
9
. Hole
11
is an opening in spacer
7
at the location of the electrical contact
10
. When membrane layer
8
is pushed downward in the area above electrical contact
10
membrane layer
8
is distorted downward placing electrical contact
10
in the ON state.
As shown in
FIG. 7
, stabilizer
4
is affixed on each of the left and right sides of the click rubber
6
(left and right as seen from the key switch operating position). Two long and narrow flat pieces
15
and
16
are arranged to form X-shaped part
18
. Flat pieces
15
and
16
may be made from a rigid material such as metal, hard plastic or the like. Stabilizer
4
formed as X-shaped part
18
is linked at an intermediary point by a support axis
17
allowing stabilizer
4
to have a variable crossing angle &agr;. Slider
20
is circular and perpendicularly protrudes from the bottom end of each X-shaped part
18
. Four sliding portions or sliders
20
a
-
20
d
are contained in a free-fitting state within the square-shaped free motion range limiter
13
respectively located at four points around the hole
12
in frame
3
.
The width W of the free motion range limiter
13
described above is slightly greater than the width of the slider
20
. The length of free motion range limiter
13
must be relatively substantial in order to allow the bottom of key top
5
to make contact with the top surface of frame
3
. Thus, slider
20
is able to move freely while sliding on the surface of membrane layer
8
within free motion range limiter
13
. A stopper (not shown) projects over free motion range limiter
13
that contains slider
20
, such that the slider
20
does not jump out of free motion range limiter
13
.
Frame
3
identified above is affixed to the top of membrane switch
2
and has a flat shape. Hole
12
is an opening in frame
3
that is positioned above electrical contract
10
of membrane switch
2
. Moreover, in addition to free motion range limiter
13
, there is a slit shaped storage hole
21
for the X-shaped part that connects two free motion range limiters
13
on each side of click rubber
6
. More specifically, X-shaped part storage hole
21
a
connects the two free motion range limiters
13
on one side of click rubber
6
and X-shaped part storage hole
21
b
connects the two free motion range limiters
13
on the other side of click rubber
6
, as shown in FIG.
7
. There is also a notch in storage hole
21
at the position at which stabilizers
4
are linked.
As shown in
FIGS. 5-7
, slider
22
is circular and protrudes perpendicularly from the both top ends of each X-shaped part
18
. As shown in FIG.
5
, slider
22
loosely fits within the horizontal part of L-shaped engagement piece
23
that is disposed at the four corners of the bottom surface of key top
5
. The distance between hanging portion
24
on the side of key top
5
and the vertical portion of engagement piece
23
is sufficiently greater than the diameter of slider
22
. This distance allows slider
22
to move freely between hanging portion
24
and vertical portion of engagement piece
23
while sliding on the bottom surface of key top
5
or on the horizontal portion of engagement piece
23
.
X-shaped part
18
is linked to frame
3
and key top
5
so as to be able to move freely within a fixed range on the surface that contains it. The arrangement, dimensions, and shape of each of the parts which control the range of play are selected so that sliders
20
and
22
have a predetermined positional relationship to free movement range limiters
13
when key top
5
is in the OFF or normal state and in the ON or compressed state.
This prior art key switch design, however, has several disadvantages. As shown in
FIG. 6
, key top
5
may be depressed so that X-shaped part
18
is compressed until the crossing angle &agr; is 180 degrees and key top
5
cannot be depressed further. At this point, lower end slider
20
of X-shaped part
18
is in a position whereby it contacts free motion range limiter
13
outside wall surface
13
b,
and top end slider
22
is in a position whereby it contacts key top
5
side hanging portion
24
. As a result, further displacement is prevented and key top
5
is stopped at that position.
While the height reduction technique for the prior art key switch described above has affected the size and weight reduction of personal computers, frame
3
in such switches overlaps and tightly adheres to the upper portion of the membrane switch
2
. As a result, even when free motion range limiter
13
outside wall surface
13
b
is extended and key top
5
bottom surface contacts the upper surface of frame
3
, the overall key switch thickness cannot be brought below the sum of key top
5
height (including the side hanging portion
24
) and the respective thickness of frame
3
, membrane switch
2
, and reinforcing base plate
1
, thus limiting the ability to reduce key switch thickness or height further.
Another disadvantage is that although the spreading width W of free motion range limiter
13
is only slightly larger than the width of slider
20
. However, a substantial amount of lengthwise space is required so as to allow key top
5
to make contact with the top surface of frame
3
when key top
5
is fully depressed. As a result of this substantial lengthwise space in free motion limiter
13
, when key top
5
is depressed the direction of movement for key top
5
differs depending on whether the force applied to key top
5
is exerted towards a the keyboard operator or away from the keyboard operator. In oth
Obara Rikuro
Osada Masamitsu
Yoneyama Masayuki
Enad Elvin
Klaus Lisa
Knight, Esq. Lisa M.
Lutzker, Esq. Joel E.
Minebea Co. Ltd.
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