Browse Prior Art Database

Electromagnetic Keyboard

IP.com Disclosure Number: IPCOM000091043D
Original Publication Date: 1969-Sep-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Steckenrider, RN: AUTHOR

Abstract

This electromagnetic keyboard eliminates many technical problems associated with contact type keyboards. It includes an encoder. The keyboard has main frame member F which supports a plurality of keys 1...7. Frame F is made of a magnetic material. Winding WP magnetically couples F to an AC source. Keys 1...7 are supported in the position shown by springs S. When a key is depressed, a flux path through the key stem is completed. The completed path is coupled to one or more secondary windings WS wound around the key stems. These windings can be printed on circuit boards and stacked between the upper and lower walls of F. Windings WS on each board are serially connected and oppositely wound in pairs to reduce induced noise.

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Electromagnetic Keyboard

This electromagnetic keyboard eliminates many technical problems associated with contact type keyboards. It includes an encoder. The keyboard has main frame member F which supports a plurality of keys 1...7. Frame F is made of a magnetic material. Winding WP magnetically couples F to an AC source. Keys 1...7 are supported in the position shown by springs S. When a key is depressed, a flux path through the key stem is completed. The completed path is coupled to one or more secondary windings WS wound around the key stems. These windings can be printed on circuit boards and stacked between the upper and lower walls of F. Windings WS on each board are serially connected and oppositely wound in pairs to reduce induced noise. Where an odd number of windings are needed a dummy no-signal winding can be employed to provide noise cancellation. The serially connected windings on each board are connected to sense amplifiers SA which detect the induced currents in windings WS. When key 1 is depressed, a magnetic path is completed through associated winding WS which is connected to SA1. This provides an output due to the induced currents in winding WS. The other sense amplifiers do not provide outputs since the connected windings are not linked to a complete flux path. When key 3 is depressed, amplifiers SA1 and SA2 provide an output. Eight stacked boards and eight sense amplifiers are capable of providing a full alphanumeric set.

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