The subject invention relates to keyboards and more particularly to a flexible-contact keyboard which is compact in nature and yet capable of bearing several hundred keys.
In the prior art, keyboard key structure is known wherein a circuit path is closed between a plurality of spaced apart contact elements by pressing down on a flexible overlying member bearing a conductive coating. Typically, a small number of such keys, for example, ten to twelve, are constructed on a surface to form a keyboard. Certain of the contact elements of each key are connected in common on the surface, while other contact elements are connected to respective separate conductive paths which arrive randomly across the surface and connect to contact pins extending out of the keyboard structure.
Attempting to apply the prior art keyboard structure to a large compact keyboard raises several problems. First, the typically-used key structure proves to be too large for compaction requirements. Secondly, registration problems occur in attempting to lay out a very large keyboard. However, the foremost problem is that the lead pattern for interconnecting to external circuitry associated with the keyboard becomes enormously complex when constructed according to prior art techniques. The space required for such circuitry in a keyboard necessary for representing a large number of characters, for example, such as the Japanese alphabet exceeds the space required for the elements themselves. Thus, the object of compaction is defeated.