FI72407B - TANGENTKOPPLINGSKONSTRUKTION - Google Patents

Description

1 72407 Key switch design. - Tangent coupling construction.

The invention relates to a key switch structure comprising a key cap and a buckle spring resembling a truncated cone between them, made of silicone rubber or other flexible material.

The invention makes it possible to combine in the same coupling structure a known capacitive coupling principle, a tactile feedback curve typical of a buckling spring and an adequate seal against splashes and debris.

A structure is already known in which a metal coil spring (e.g. DE-3007239, US-3797630 Zilkha and US-4277780 Sonderman) is placed in said location. The disadvantage of this otherwise long-lasting and reliable structure is, in addition to the poor sealing, the inappropriate motion-force curve shown in Fig. 2, in which the motion tends to stop at the point of discontinuity at the coupling point. This easily causes vibration on both sides of the switching point and results in two or more identifiable connections.

In another prior art construction (DE-3007239), a truncated cone-shaped silicone rubber spring is placed under all the moving parts of the coupling and its closed upper end has a spot made of conductive rubber which galvanically connects the two conductors on the plate below it. In this structure, it is not possible to use the capacitive coupling principle because the conductive area cannot be made large enough in area to provide reliable operation because the conical spring needs space from the same area. Said galvanic contact switch, on the other hand, is not long enough for the most demanding applications, as its duration is typically considered to be a few million functions, up to a maximum of ten million, while the capacitive principle achieves at least 100 million operations per touch point.

One prior art construction (EURO-0064240) uses the rubber spring described above without a conductive part and constructs a capacitive coupling under it from a plurality of printed or perforated plastic films. In this way, the structure becomes complicated and since the contacting parts are at their farthest distance from the thickness of only one perforated plastic film (approx. 0/1 mm), unintentional connections are easily caused by thermal, moisture and mechanical stresses. Because the uppermost membrane has to be bent even during connection, the life of the coupling is limited, according to the manufacturer's own statement, 30 million connections.

In order to eliminate the above drawbacks, the key switch according to the invention is characterized by the things set forth in the characterizing part of claim 1.

The invention will now be described with reference to the accompanying drawings, in which:

Figure 1 shows the structure of a key switch according to the invention in cross section

Figure 2 shows the movement force curve of a key switch with a coil spring known per se

Figure 3 shows a movement curve of a key switch according to the invention.

According to Figure 1, a key switch according to the invention comprises: a key cap 1, a cup-shaped body 4 and a buckling spring 2 placed between them; a slide 3 passing through an opening in the upper surface of the body 4, and a post-coupling spring 5 connected thereto provided with a capacitive coupling part 7; a switch matrix 8 on the base plate 9 and a support plate 6.

The buckling spring 2, preferably made of silicone rubber, is shaped 3 72407 in the shape of a nearly truncated cone to achieve the desired spring properties and at both ends almost cylindrical to provide adequate attachment, support and sealing. The spring 2 is mounted with the wider end facing upwards to fit in place and provide adequate support and sealing and prevent side view. Thus, the structure of the lower end of the switch remains completely freely selectable, so that a conventional capacitive switch structure with post-springs 5 and large-area capacitance diaphragms 7 connected to the key cap 1 by a pin-like sliding part 3 passing through the opening in the upper surface 4 can also be placed there. In order to achieve reliable operation, the diameter of the capacitance film 7 should preferably be more than 10 mm. The buckling spring 2 also forms a seal between the key cap 1 and the body 4 around said opening. The lower edge of the cup-shaped body 4, which surrounds the downwardly opening coupling opening, is sealed against the base plate 9 supporting the coupling matrix 8 by pressing. This sealing can also be done, for example, by gluing or making the frame 4 fixed to the support plate.

Using the spring structure according to the invention, a very low structure can also be achieved, because the essential structural parts, such as the spring, are located under the hat in an otherwise empty space.

Figure 3 shows the spring force curves of the structure according to the invention. The arrangement of the buckling spring 2 according to the invention makes it possible both to form it in the shape of a nearly truncated cone and thus with spring properties as shown in Fig. 3 and to place e.g. a foam spring 5 When the coupling point can thus be placed at the desired location on the descending part of the spring curve, where the coupling cannot easily be held, accidental couplings can be prevented and a clear closed or open signal can be obtained from the coupling.

Claims (4)

72407 A button coupling structure comprising a key cap (1), a body (4) and a truncated cone-shaped buckling spring (2) made of silicone rubber or other flexible material, characterized in that the buckling spring (2) is located wider the end upwards mainly inside the key cap (1), the narrower lower end corresponding to the cup-shaped and opening downwards with its coupling opening downwards. A key switch structure according to claim 1, comprising a post-movement spring (5) made of a flexible material such as foam, with a capacitive coupling part (7), characterized in that a post-movement spring (5) and a buckling spring arranged inside the cup-shaped body (4) (2) the spring force curve based on the interaction is decreasing at the coupling point (Fig. 3). A key switch structure according to claim 1 or 2, wherein the key cap engages a switch portion (7) within the body (4) with a pin-like slide portion (3) passing through an opening in the upper surface of the body (4), characterized in that the buckling spring (2) forms a seal between the key cap (1) and the body (4) around said opening. A key switch structure according to claim 3, characterized in that the lower edge of the cup-shaped body (4) surrounding the downwardly opening connection opening is sealed against the base plate (9) supporting the switch matrix (8) by gluing, pressing on the support plate (6) or 6) as an integral part.