Tactile element and keyboard including the tactile element

A tactile snap-action key which is movable between an opened and closed position to open and close an electrical circuit, said key comprising:

• a sheet of base material;
• a tactile element formed in said sheet of said base material and including a first arcuately shaped invertible dome and a dome actuating protrusion means, said dome actuating protrusion means being a second arcuately shaped dome which is integral with and extending from said first dome, said first dome being inverted by applying a pressure against said second dome, said second dome having a smaller radius than said first dome, the ratio of the radius of said second dome to the radius of the first dome being selected such that said second dome will not be inverted by said applied pressure, said first dome providing for tactile feedback when it is inverted, the surface of said second dome being smooth and uninterrupted and the surface of said first dome being smooth and interrupted only by the circular junctions with said sheet of base material and the second dome;
• first conductive means being associated with said first dome;
• and
• second conductive means, said second conductive means being aligned with and facing said first conductive means, the actuation of the key providing said applied pressure against said second dome which at least partly inverts said first dome establishing electrical contact between said first conductive means and said second conductive means.

A keyboard comprising:

• a flexible first sheet of printed circuitry having a plurality of tactile elements, each element including a first arcuately shaped dome which is integral with and extends outwardly from said first sheet and a dome actuating protrusion means which is integral with and extends from said first dome, said dome actuating protrusion means being a second arcuately shaped dome, said first and second domes meeting at a circular junction and having smooth uninterrupted surface contours, said first dome being at least partly inverted by applying a pressure against said second dome, said second dome having a smaller radius than said first dome, said radius of said second dome being sufficiently less than the radius of said first dome to prevent inversion of said second dome by said applied pressure;
• a portion of printed circuitry carried by each of said first domes;
• and
• circuit means aligned with said tactile elements and retained with respect to said first sheet, the printed circuit portions carried by said first domes contacting the circuit means when each of said first domes is partly inverted.