Flexible membrane circuit structure for keyswitch

Details Flexible membrane circuit structure for keyswitch Flexible membrane circuit structure for keyswitch

1999-09-10

2001-01-02

Friedhofer, Michael (Department: 2832)

Electricity: circuit makers and breakers

Multiple circuit control

Multiple switch

C200S0050EA

Utility Patent

active

06169255

ABSTRACT:

FIELD OF THE INVENTION
The present invention relater to a flexible membrane circuit structure for keyswitch, especially to a flexible membrane circuit structure for low-profile keyswitch, by which the cost is reduced and the endurance is enhanced.
BACKGROUND OF THE INVENTION
The portable electronic apparatus such notebook computer, electronic dictionary and PDA generally use low-profile keyboard to enhance the portability thereof These low-profile keyboards generally uses flexible membrane circuit with single layer, double layer or triple layer structure to minimize the height thereof. In the flexible membrane circuit with double layer or triple layer structure, there are an upper membrane circuit layer and a lower membrane circuit layer each with a plurality of conductive contacts corresponding to the location of the keyswitch to be assembled on the upper membrane circuit and the lower membrane circuit. More particularly, in the flexible membrane circuit with double layer structure, a circular spacer is arranged around one conductive contact on the upper or lower membrane circuit layer. In the flexible membrane circuit with triple layer structure, a spacer layer with a plurality of through holes each corresponding to one conductive contact is sandwiched between the upper and lower membrane circuit layer. However, in the flexible membrane circuit with double layer or triple layer structure, the upper and lower membrane circuit layer with printed circuit thereon are separately formed and then the upper and lower membrane circuit layer with printed circuit are assembled. The manufacture is complicated and the cost is high.
As shown in FIG.
1
and
FIG. 1A
, the above-mentioned problem can be solved by using a larger flexible membrane circuit layer composed of two upper membrane circuit layers bridged by a plurality of folded plates
12
. Therefore, the area of the larger flexible membrane circuit layer is about two times of an upper membrane circuit layer
10
or a lower membrane circuit layer
11
in previously-described keyboard. The circuit trace is formed on the surface of the larger flexible membrane circuit and then the larger flexible membrane circuit is folded by bending the folded plates
12
such that a connected upper membrane circuit layer
10
and lower membrane circuit layer
11
is formed. Moreover, a spacer layer
13
can be provided between the upper membrane circuit layer
10
and the lower membrane circuit layer
11
. However, when assembled in a keyboard
1
, the folded plates
12
are arranged on the edge of the keyboard
1
and between the movable keytop
14
and the substrate
15
of the keyboard
1
. As shown in
FIGS. 2 and 3
, the folded plates
12
are subjected to repeated striking force of the movable keytop
14
such that the bent portion
120
of the folded plate
12
is probably broken.
It is an object of the present invention to provide a flexible membrane circuit structure for low-profile keyswitch, by which the above mentioned problems are solved, and the keyboard cost is reduced.
To achieve above objects, the present invention provides a flexible membrane circuit structure for keyboard comprising a substrate; a membrane circuit structure arranged on the substrate and comprising an upper membrane layer and a lower circuit layer, a plurality of movable keytops depressibly arranged on the substrate and each corresponding to one the conductive contact; at least one fixed keytop arranged on marginal location of the keyboard and being not depressible. Each membrane circuit layer has conductive contacts. The conductive contacts on the upper membrane layer has a predetermined separation with corresponding conductive contacts on the lower membrane layer. The upper membrane layer and the lower circuit layer is bridged by at least one folded plate such that the upper membrane layer electrically and mechanically connected with the lower circuit layer. The folded plate received within the fixed keytop to prevent the breaking of the folded plates.
The various objects and advantages of the present invention will be more readily understood from the following detailed description when read in conjunction with the appended drawing, in which:


REFERENCES:
patent: 4450324 (1984-05-01), Fukukura et al.
patent: 4837412 (1989-06-01), Tachibana
patent: 4901193 (1990-02-01), Kinugawa et al.
patent: 6057517 (2000-05-01), Meyer

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