Keyboard

#1. Field of the Invention

#The invention relates to a keyboard.

#2. Brief Description of the Prior Art

#The invention will be described more specifically hereinafter with reference to embodiments and to the drawings.

#FIG. 1 is a cross-sectional view of a keyboard.

#FIG. 2 is an enlarged view of the key with actuating button.

#Reference numeral 1 as used in the figures denotes a base plate or foil for a keyboard of an insulating substrate such as, e.g., hard paper or plastic, on which conductor paths 2 and contact areas 3 have been provided in desired patterns by conventional techniques. Above this base plate or foil an insulating layer or also an insulating foil or insulating plate 4 is superposed, which has recesses or cutouts at the positions of the contact areas 3. To anchor said insulating plate to the base plate, at least partial areas thereof are adhered to one another. If an insulating layer is used, this layer can be applied by screen printing. Above the insulating foil or insulating plate 4 a metal frame 7 is positioned, which has a number of embossed protrusions 8. These protrusions are interconnected by grooves 11 serving to equalize the pressure. If this possibility of equalizing pressure would not exist, the key, once pressed, no longer would return immediately into its starting position.

#Each of these protrusions has a central opening 9 in which a preferably circular snap member 5 is held. This snap member is made from a rubber-elastic material, especially silicon rubber, and, as can be seen from the figures, comprises a curved edge portion which has a concave or convex curvature or may also have the shape of a truncated cone, as well as a substantially flat upper portion. The snap member functions according to the well-known snap-back principle. During manufacture all snap members are mounted in the metal frame 7 by injection molding in a single operation. Injection molding of the snap members is effected such that the openings 9 are completely closed or sealed by the snap members. By this mounting technique, combined with the adhering of the base plate, the contact areas are protected against detrimental environmental influences. On the other hand, however, this technique calls for the already mentioned equalization of pressure by means of the grooves 11. The protrusions 8 protruding from the metal frame have the function of providing a connection to the grooves 11, while the sealing effect caused by the injection molded snap members is retained.

#On the underside of the snap member 5 a contact element 6 is provided, which is made from an electrically conductive material, preferably an electrically conductive silicon rubber, and which is to establish an electrical connection between the contact areas 3 when the snap member has been pressed. This contact element may be prefabricated and formed, e.g., by punching. It can be inserted prior to injection molding into the mold in cavities provided for this purpose and bonded to the subsequently injected silicon rubber by vulcanization or also by subsequent adhering to the snap member. Apart from this, manufacture and mounting of the electrically conductive contact element according to the principle of the two-color injection molding method would be feasible.