Capacitive keyboard
US4458293A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | May 17, 1982 |
| Grant date | Jul 3, 1984 |
| Priority date | — |
| Expiry date | May 17, 2002 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01H2235/00
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
An improved capacitive keyboard includes a plurality of switch keys that each define a minimum capacitance when in a fully extended rest state and a maximum capacitance when pressed. Each switch key has a plunger mechanism that compresses a capacitive spring when the key is pressed and releases the spring when the key is released. Each capacitive spring is affixed in operational orientation over an associated capacitive pad by soldering areas of the base coil of the spring to adjacent plated holes in a supporting printed circuit board. In operation, molten solder is applied at the underside of the printed circuit board and passes up through the plated holes by capillary action to contact the base coil of the spring. The hardened solder holds the spring in its operational position on the printed circuit board and conductively contacts the spring with an output terminal of the board.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.