JPS6343709Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and improved structure of a sheet-like switch cover member.

In recent years, as a keyboard device for various electronic devices, a printed circuit board with a plurality of fixed contacts is provided with a plurality of dome-shaped structural parts, and the ceiling of the dome carries a movable contact that faces the fixed contacts. A keyboard device having a structure in which a sheet-like switch cover member made of an integrated insulating elastomer is placed and integrated has come to be widely used.

In addition, in order to simplify the configuration of the printed circuit board in the keyboard device, improve its mounting density, and make the keyboard device inexpensive, some of the circuits on the printed circuit board are removed from the sheet. A switch cover member that is moved to the surface of a switch cover member, specifically a sheet switch cover member that has a strip-shaped thin film circuit (usually a common circuit) that extends from the movable contact point to the flat part of the dome via the inner wall surface of the dome. It has been known.

However, in the switch cover in which a thin film circuit is provided on the wall surface of the dome-shaped structure as described above, the thin film circuit is usually made of a material such as conductive paste that is harder and more brittle than the insulating elastomer that constitutes the switch cover. Due to the structure of the dome, repeated buckling deformation caused by key operations can cause significant damage to the thin film circuit on the dome wall.
Therefore, it has a drawback of being inferior in durability.

The present invention provides a new and improved sheet-like switch cover member capable of eliminating such drawbacks, which is made of an insulating elastomer sheet having a dome-like structure, and is movable on the ceiling of the dome. In addition to supporting and integrating contacts, a thin film circuit is provided that extends from the contact point to the flat portion via the inner wall surface of the dome, and the buckling load of the dome wall portion where the thin film circuit is provided is greater than that of other dome wall portions. It is characterized by this.

Hereinafter, the present invention will be described in detail based on the accompanying drawings.

The attached drawings show an embodiment of the sheet-like switch cover according to the present invention, in which Fig. 1 is a partial sectional view thereof, and Fig. 2 is a bottom view thereof.
2 is a movable contact provided on the ceiling of the dome; 3 is a thin film circuit made of conductive paste, for example, provided on the inner wall of the dome so as to extend from the contact to the flat portion 4; and 5 is a thick wall. This is the key top part.

As is clear from FIG. 1, in this sheet-like cover member, the dome wall portion 6a provided with the thin film circuit 3 is formed thicker than the other dome wall portion 6b, and the seat of the dome wall portion 6a is The bending load is made larger than the buckling load of the other portion 6b.

In addition, in the present invention, in order to achieve the intended purpose, the dome wall portion 6 provided with the above-mentioned thin film circuit 3 is
It is desirable that the wall thickness of the dome a be five times or more that of the other dome wall portion 6b, and that the area of the thin film circuit 3 covering the dome portion be less than half of the dome.

In the above sheet-like switch cover member, when a pressing force is applied to the key top portion 5 during key operation, the thick dome wall portion 6
A is hardly deformed, and the other thin portion 6b is mainly buckled and deformed, and the movable contact 2 is pressed down. In this way, the thick-walled dome wall portion 6a, and therefore the thin film circuit 3 disposed therein, hardly undergoes buckling deformation despite the key operation, so it does not suffer any damage and can be used for a long period of time. Not only can stable electrical characteristics be maintained over a period of time, but also the key top portion 5 is always pushed in a certain direction (diagonal push).
This also provides an extremely stable key feel for the person operating the keys.

In addition, although the drawing illustrates a case where the buckling load in the circumferential direction of the dome is changed by changing the wall thickness in the circumferential direction of the dome,
The present invention is not limited to this, but for example, the dome wall portion 6a provided with the thin film circuit 3 is made almost vertical, and the other portion 6b is inclined to change its buckling load. Of course it's a good thing. In addition, although FIG. 1 shows an example in which the surface of the movable contact 2 that contacts the fixed contact is a surface that is approximately parallel to the printed circuit board surface 7, this contact surface is such that the key top portion 5 is always in a constant direction. The key top may be curved in relation to being pressed at an angle, or it may be pre-inclined to match the inclination of the key top so that both contact surfaces match exactly when contacting the fixed contact. You can stay there. Furthermore, although the drawings illustrate a single movable contact on the ceiling of each dome structure, it should be understood that a plurality of movable contacts may be provided.

As explained above, the sheet-like switch cover member of the present invention makes the buckling load of the dome wall portion where the thin film circuit is provided larger than that of the other dome walls, thereby causing the thin film circuit to buckle when a key is operated. Since it is designed to avoid buckling deformation as much as possible, it can significantly improve the durability of the thin film circuit compared to conventional products of this type, and it also provides stable key feeling, so its practical value is extremely large. .

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of one embodiment of the sheet-like switch cover member of the present invention, and FIG. 2 is a bottom view thereof. 1...Dome-shaped structural part, 2...Movable contact, 3
. . . thin film circuit, 4 . . . flat portion, 5 . . . key top portion, 6 a .

Claims (1)

[Scope of utility model registration request] A sheet-like switch cover member comprising an insulating elastomer sheet having a dome-shaped structural portion, a movable contact being supported and integrated on the ceiling of the dome, a thin-film circuit being provided which connects the contact to a flat portion via the inner wall surface of the dome, and the buckling load of the dome wall portion on which the thin-film circuit is provided is made greater than that of other dome wall portions.