Preh Elektrofeinmechanische Werke Jakob Preh Nachf Gmbh & Co.

Karl-Heinz Claassen

Jurgen Oelsch

Richard Volk

A process for the manufacture of a contact mat suitable for a keyboard or ypad is described. This contact mat is produced by the injection-moulding process and consists of a sheet-like composite body made of an electrically non-conductive two-component silicone rubber, and at least one carrier part, which is elastically deformable when pressure is applied to a key and is moulded out in the shape of a calotte. On the inside of the carrier part and in the pole region, there is a contact component which is made of an electrically highly conductive material. When the carrier part is depressed, an electrical connection is made via the contact component between the contact surfaces of a printed circuit located below the contact mat. In order to be able to manufacture the contact component in a simple manner and without waste, the contact component is made in an injection mould, wherein the entire lower mould part is at a temperature above the vulcanization temperature of the contact component. The upper cavity plate of the corresponding upper mould part consists of two halves of which one half is at a temperature below the vulcanization temperature. The contact component is produced by means of this half. Subsequently, a lower cavity plate of the lower mould part is rotated from this first into a second position, and the composite body and the carrier body are then moulded. This half of the upper cavity plate is at a temperature above the vulcanization temperature. Accordingly, all the curable components are vulcanized separately, even though they are moulded in the same mould.

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Wulfershausen, Germany

Karl-Heinz Claassen