US3848252A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnetic keyboard
Assignee: International Business Machines Corp
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Filing: 1972-02-24
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Granted: 1974-11-12
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Expires: 1992-02-24
Abstract
Abstract A keyboard is provided with a plurality of manually operable keys each having a ferromagnetic member movable to and from a position in the space between a permanent magnet and a magnetosensitive element. The position of the ferromagnetic member thereby affects the flux density of the magnetic field at the respective magnetosensitive element. A circuit generates an electrical signal in response to the magnitude of the flux density at each of said magnetosensitive elements and thereby in response to the manual operation of each of said keys.
Inventors
- 👤 R Suelflow
- 👤 H Chang
- 👤 R Strnad
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-22 19:07
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/965; H03K17/97; H03K17/972
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
205 words
A keyboard comprising a plurality of manually operable keys, a frame, means movably mounting said keys to said frame, a plurality of Hall-effect devices each associated with a respective one said keys for providing a change in voltage in response to a change in the magnetic flux density in the region of said Hall-effect device, a plurality of sources of magnetic flux each associated with a respective one of said Hall-effect devices, said magnetic flux extending from each of said sources to its respective Hall-effect device, each of said keys having a ferromagnetic member connected thereto and movable from a first position to a second position in response to manual operation of said key, the magnitude of the flux density at said respective Hall-effect device being responsive to the position of said ferromagnetic member, a plurality of differential amplifiers each having input nodes connected across a respective one of said Hall-effect devices so as to amplify said voltage change provided in response to said change in magnetic flux density, and a plurality of trigger circuits each connected in cascade to a respective one of said differential amplifiers so as to convert the analog output signal of the respective differential amplifier to a binary digital signal.
Claim 2
Dependent Claim
205 words
A keyboard comprising a plurality of manually operable keys, a frame, means movably mounting said keys to said frame, a plurality of Hall-effect devices each associated with a respective one said keys for providing a change in voltage in response to a change in the magnetic flux density in the region of said Hall-effect device, a plurality of sources of magnetic flux each associated with a respective one of said Hall-effect devices, said magnetic flux extending from each of said sources to its respective Hall-effect device, each of said keys having a ferromagnetic member connected thereto and movable from a first position to a second position in response to manual operation of said key, the magnitude of the flux density at said respective Hall-effect device being responsive to the position of said ferromagnetic member, a plurality of differential amplifiers each having input nodes connected across a respective one of said Hall-effect devices so as to amplify said voltage change provided in response to said change in magnetic flux density, and a plurality of trigger circuits each connected in cascade to a respective one of said differential amplifiers so as to convert the analog output signal of the respective differential amplifier to a binary digital signal.
Claim 3
Dependent Claim
137 words
A keyboard as set forth in claim 1 wherein each of said differential amplifiers comprises a pair of transistor each having a base, collector and an emitter, each of said Hall-effect devices having a first pair of opposite faces and a second pair of opposite faces extending perpendicular to said first pair of faces, means connected to said first pair of faces of each Hall-effect device to supply current therethrough, said bases of each pair of differential amplifier transistors being connected to said second pair of faces of the respective Hall-effect device, a current source connected to the emitters of each pair of differential amplifier transistors, a load resistor connected to a collector of at least one transistor of each pair of differential amplifier transistors, and conductive means connecting said last-recited collector to the respective trigger circuit.
Claim 4
Dependent Claim
43 words
A keyboard as set forth in claim 2 wherein each of said trigger circuits is a Schmitt trigger circuit including two transistors having mutually-coupled emitters, one of said Schmitt trigger circuit transistors having a base coupled to said last-recited differential amplifier transistor collector.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-11 | 1978-05-13 | 1978-11-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-11 | 1982-05-13 | 1982-11-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-11 | 1986-05-13 | 1986-11-12 | $7700.00 | Window Closed / Lapsed |