Typewriting machines – Key-board or key lever-actuating mechanism – Key-cap or key-stem structure
Reexamination Certificate
2003-03-06
2004-02-10
Hirshfeld, Andrew H. (Department: 2854)
Typewriting machines
Key-board or key lever-actuating mechanism
Key-cap or key-stem structure
C400S491200, C400S491300, C361S689000, C174S261000, C174S262000, C174S250000, C174S267000
Reexamination Certificate
active
06688790
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to keyboard input device and, particularly, to a keyboard input device used as an input device for personal computers.
2. Description of the Related Art
Thin keyboard input devices usually adapted to notebook type personal computers, have been proposed in a variety of kinds in which a pair of lever members are intersecting being linked together so as to serve as members for supporting the key tops and being resiliently urged upward by hollow rubber springs, in a manner that the intersecting angles of the pair of lever members that are linked together vary accompanying the ascending/descending motion of the key tops.
There has been proposed a keyboard input device in which, for example, a lever member of which the upper end is rotatably engaged with the back surface of the key top and another lever member of which the upper end is slidably engaged with the back surface of the key top, are linked together at their intersecting portions, and the key tops are supported by the pair of integrated lever members so as to be moved up and down.
Referring to
FIG. 6
, the switching unit of the keyboard input device of this kind has a dome-like hollow rubber spring
21
, and wherein a moving contact
21
b
is formed at the ceiling portion
21
a
in the cavity of the rubber spring
21
.
The rubber spring
21
is adhered to a switch board
22
with an adhesive over the whole circumference of a lower end
21
d
of a skirt-like outer peripheral wall
21
c
thereof.
The switching board
22
has a pair of fixed contacts
22
a
and
22
a
at a portion facing the moving contact
21
b
so as to produce the switching operation upon contacted by the moving contact
21
b.
In the switching board
22
, further, a first circuit pattern
22
b
and a second circuit pattern
22
c
that are running being connected to the pair of fixed contacts
22
a
and
22
a
, are partly laminated in two layers as shown in FIG.
7
.
The first circuit pattern
22
b
is provided with a first insulating layer
23
comprising two resist layers covering the upper portion thereof. On the first insulating layer
23
is formed a second circuit pattern
22
c
traversing (crossing) the first circuit pattern
22
b
, and on the second-circuit pattern
22
c
is formed a second insulating layer
24
.
The first and second circuit patterns
22
b
and
22
c
which are locally formed in two layers, inclusive of the first and second insulating layers
23
and
24
, are protruding having a height A from the surface of the switching board
22
.
Even when the first circuit pattern
22
b
of a single layer is formed as shown in
FIG. 8
, the switching board
22
protrudes to a height B though it is smaller than the height A.
On the switching board
22
of a portion to where the rubber spring
21
is adhered, further, there is placed a lever-mounting plate
25
mounting a pair of lever members (not shown) intersecting in an X shape being linked together so as to ascend and descend.
As shown in
FIGS. 7 and 8
, the lever-mounting plate
25
is placed on the first and second circuit patterns
22
b
and
22
c
of the two-layer structure, or on the first circuit pattern
22
b
of the one-layer structure.
The switching board
22
mounting the above lever-mounting plate
25
is placed on a flat metal plate
26
and is supported in a housing that is not shown.
In the above conventional keyboard input device, when the key top (not shown) on the rubber spring
21
is pushed down, the outer peripheral wall
21
c
of the rubber spring
21
undergoes the elastic deformation permitting the moving contact
21
b
to descend.
Then, the moving contact
21
b
comes in contact with the pair of fixed contacts
22
a
to turn the switch on.
In the conventional keyboard input device in which the lever-mounting plate
25
is mounted on the insulating layers
23
and
24
that are partly protruding maintaining a height A or B above the surface of the switching board
22
, however, the attitude of the lever-mounting plate
25
loses stability, the lever-mounting plate
25
rattles when the key top is depressed, and the feeling for depressing the key top is deteriorated.
Besides, since the first and second insulating layers
23
and
24
are protruding to a height of A or B, a depression of the key top causes the load of depression to be locally and repetitively exerted on the first and second insulating layers
23
and
24
.
Due to the load of depression locally and repetitively exerted, therefore, cracks develop in the first and second insulating layers
23
and
24
, whereby the second circuit pattern
22
c
formed on the first insulating layer
23
is broken and the breakdown voltage characteristics are deteriorated.
Or, water infiltrates through the cracks causing the first and second circuit patterns
22
b
and
22
c
to be corroded and broken.
SUMMARY OF THE INVENTION
This invention was accomplished in view of the above problems, and has an object of providing a keyboard input device of a high quality maintaining good feeling of operation when the key tops are depressed and suppressing the occurrence of cracks in the insulating layers on the circuit patterns.
As a first means for solving the above problem, a keyboard input device of the invention comprises a pair of lever members rotatably coupled at their intersecting portions, a lever-mounting plate for supporting the lower ends of the pair of lever members in an engaged manner, a circuit board on which the lever-mounting plate is placed and is forming a circuit pattern on a surface facing the lever-mounting plate, a hollow rubber spring mounted on the circuit board, and a key top supported by the pair of lever members and is urged by the elastic urging force of the rubber spring in a direction to separate away from the circuit board, wherein the circuit board forms an insulating layer for insulating and covering the circuit pattern, the insulating layer having a surface area larger than that of the lever-mounting plate permitting the lever-mounting plate to be placed thereon.
The insulating layer is constituted by at least two or more resist layers formed being laminated on the circuit board inclusive of the circuit pattern.
The insulating layer forms a protruded portion by causing the resist layer to be protruded on the circuit pattern, a dummy layer of a size equal to the height of the protruded portion is formed on the slope portions around the protruded portion, and an uppermost layer comprising the resist layer is laminated on the dummy layer and on the protruded portion.
REFERENCES:
patent: 3983022 (1976-09-01), Auyang et al.
patent: 4470874 (1984-09-01), Bartush et al.
patent: 4956313 (1990-09-01), Cote et al.
patent: 4973562 (1990-11-01), Den Blanken
patent: 5441094 (1995-08-01), Pasch
patent: 5584740 (1996-12-01), Hsu et al.
patent: 6528874 (2003-03-01), Iijima et al.
patent: 61049491 (1986-03-01), None
patent: H7-245454 (1995-09-01), None
Alps Electric Co. ,Ltd.
Brinks Hofer Gilson & Lione
Evans Andrea H.
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