Electricity: circuit makers and breakers – Multiple circuit control – Multiple switch
Reexamination Certificate
2002-06-18
2003-12-02
Enad, Elvin (Department: 2832)
Electricity: circuit makers and breakers
Multiple circuit control
Multiple switch
C200S512000, C200S341000, C400S491000
Reexamination Certificate
active
06657139
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a keyboard for use as an input device of a computer and other similar devices and, more particularly, to a novel keyboard structure that achieves the low profile and the light weight.
FIG. 1
shows a conventional keyboard structure, which is identical with that proposed by the applicant of this application in Japanese Patent Application Laid-Open Gazette No. 288639/99 entitled “Keyboard Switch.”
A description will be given first, with reference to
FIGS. 1 and 2
, of the prior art example. The illustrated keyboard is composed of a keyboard substrate
11
, a membrane switch sheet
12
, a keyboard frame
14
and an actuator
15
. The substrate
11
and the frame
14
are each made of a metal sheet. The membrane switch sheet
12
is sandwiched between the substrate
11
and the frame
14
to provide rigidity in the membrane switch sheet
12
and hold it flat.
The membrane switch sheet
12
in this example is shown to be a laminated structure of formed a pattern sheet
12
-
1
and an insulating sheet
12
-
2
. On the top of the pattern sheet
12
-
1
there are deposited contact patterns
12
A and
12
B forming a switch
12
S and a wiring pattern (not shown) for detecting the conduction
onconduction of electricity between the contact patterns
12
A and
12
B. In the insulating sheet
12
-
2
overlying the pattern sheet
12
-
1
there is made an opening
12
C through which the contact patterns
12
A and
12
B and their surrounding areas are exposed. The pattern sheet
12
-
1
and the insulating sheet
12
-
2
are sandwiched between the substrate
11
and the frame
14
with the exposed surface of the insulating sheet
12
-
2
held upward.
In the frame
14
there is also formed an opening
14
A at the position corresponding to the opening
12
C made in the membrane switch sheet
12
. Through these openings
14
A and
12
C a conduction part
18
C projecting downward from the actuator
15
makes contact with the contact patterns
12
A and
12
B to establish electric connections between them.
The actuator
15
in this example comprises pairs of first and second links
6
A and
6
B forming a pantographic lifting or support frame as depicted in
FIG. 2A
; a keytop
17
(see
FIG. 2B
) mounted atop the pair of links
6
A and
6
B; and a tactile-response collapsible rubber dome
18
which, upon depression of the keytop
17
, allows the conduction part
18
C to move down into contact with the contact patterns
12
A and
12
B and, upon removal of the downward force applied to the keytop
17
, restores the keytop
17
to the position of its top dead center.
The rubber dome
18
is composed of: a cylindrical portion
18
A of a relatively large diameter that encompasses the contact patterns
12
A and
12
B; and a dome portion
18
B with which the cylindrical portion
18
A is capped. On the ceiling of the dome portion
18
B there is protrusively provided the conduction part
18
C having a flat lower end face. When a downward force is applied to the roof of the dome portion
18
B through the keytop
17
, the dome portion
18
B becomes elastically deformed, bringing down the conduction part
18
C. Incidentally, when the dome portion
18
B is deformed to some extent, its reaction force sharply decreases due to its oilcan phenomenon, providing tactile feedback to the keytop
17
being depressed.
Reference numerals
14
B and
14
C respectively denote a pair of leg rotary shaft bearings and a pair of slide shaft bearings both formed by drawing the frame
14
. The pair of leg rotary shaft bearings
14
B rotatably receives leg rotary shafts
16
A that extend outwardly from the lower end portions of the second links
6
A at right angles thereto. The pair of leg slide shaft bearings
14
C receives leg slide shafts
16
A that similarly extend outwardly from the lower end portions of the second links
6
A at right angles thereto, the leg slide shafts
16
A being slidable parallel to the frame surface. Likewise, a pair of rotary bearings
17
A formed on the underside of the keytop
17
rotatably receives first coupling rod
16
C extending between top end portions of the pair of first links
6
B. And, a pair of slide bearings
17
B on the underside of the keytop
17
receives keytop support sliding shafts
16
D protrusively provided on the inner side surfaces of top end portions of the pair of first links
6
B, the sliding shafts
16
D being slidable parallel to the underside of the keytop
17
. The links
6
A and
6
B, the bearings
14
B,
14
C,
17
A and
17
B, and the keytop
17
constitute the pantographic support frame.
In this example, the substrate
11
and the frame
24
are fixedly joined together by: forming bumps
11
A in the substrate
11
by stamping; inserting the bumps
11
A through through holes
12
D in the membrane switch sheet
12
into contact with the underside of the frame
14
; and spot-welding the substrate
11
and the frame
14
at top surfaces or crests
19
of the bumps
11
A. That is, the bumps
11
A and the through holes
12
D are provided at plural places in the substrate
11
and in the membrane switch sheet
12
, respectively, so that the substrate
11
and the frame
14
are welded together at the plural places.
The above conventional keyboard uses an aluminum sheet for the substrate
11
and a stainless steel sheet for the frame
14
. Before the stainless steel sheet came into use as the frame
14
, a thick resin sheet had been used. The use of the thick resin sheet, however, inevitably increases the overall keyboard thickness. The use of the stainless steel sheet in place of the resin sheet permits reduction of the overall keyboard thickness. Because of its high specific gravity, however, the stainless steel sheet increases the overall weight of the keyboard.
Further reduction of the keyboard thickness and weight could be achieved by use of: a single-sheet keyboard structure in which the membrane switch sheet
12
is deposited all over the substrate
11
as of aluminum low in specific gravity and the actuator
15
is mounted directly on the top of the membrane switch sheet
12
; or a two-sheet keyboard structure in which in which the membrane switch sheet
12
is sandwiched between the substrate
11
and the frame
14
both of which are thin aluminum sheets (for example, 0.2 to 0.3 mm thick).
The present inventor studied which of the one- and two-sheet keyboard structures would be mechanically stronger. The following is cross-sectional secondary moments I
1
and I
2
of aluminum sheets with a length b and thicknesses t
1
=0.6 mm and t
2
=0.5 mm, respectively, as depicted in
FIGS. 3A and 3B
and the cross-sectional secondary moment I
3
of a laminated member of two aluminum sheets with the length b and thicknesses t
3
=0.3 mm and t
4
=0.2 mm, respectively, as depicted in FIG.
3
C.
I
1
=(
b
/12)(0.6
3
)=0.018
b
I
2
=(
b
/12)(0.5
3
)=0.010
b
I
3
=(
b
/12)(0.8
3
−0.3
3
)=0.04
b
The cross-sectional secondary moment I
3
of the laminated structure is about twice larger than the cross-sectional secondary moment I
1
of the single-sheet structure of the thickness t
1
=0.6 mm and approximately four times larger than in the case of the single-sheet structure of the thickness t
2
=0.5 mm.
In the case of the two-sheet structure, although each sheet is as thin as around 0.2 to 0.3 mm, the cross-sectional secondary moment is I
3
=0.04b about twice larger than in the case of the single-sheet structure with t
1
=0.6 mm and about four times larger than in the case of the single-sheet structure with t
2
=0.5 mm. This suggests that the two-sheet structure is greater in rigidity than the single-sheet structures. Accordingly, the two-sheet keyboard structure will achieve the low profile and light weight.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a two-sheet-structured keyboard of great rigidity.
The keyboard according to the present invention comprises:
a membrane switch sheet h
Enad Elvin
Gallagher & Lathrop
Hosiden Corporation
Lathrop, Esq. David N.
Lee K.
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