Patent US3638221A successfully refreshed from Google Patents.
US3638221A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Solid-state keyboard
Assignee: Illinois Tool Works Inc
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Filing: 1969-11-24
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Granted: 1972-01-25
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Expires: 1989-11-24
Abstract
Abstract The disclosure describes solid-state keyboards employing a saturable magnetic core switch for each key. Each key has a keystem of magnetic material, the keystem having legs extending on opposing sides of the core. Two permanent magnets are attached to the keystem. When a key is not depressed, the magnets are located adjacent opposing sides of the core so that a flux path is formed through the core, the keystem, and the two magnets, to thereby saturate the core. When a key is depressed, the permanent magnets are moved away from the core so that it becomes unsaturated. The core is threaded by one or more windings, at least one of them being excited from an AC drive source. The core and its winding or windings may act as a transformer or variable inductance. Depending upon the wiring configuration employed, a single output signal or a coded combination of output signals may be obtained when a key is actuated.
Inventors
- 👤 Victor M Bernin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 07:44
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/965; H03K17/97; G; G01; G01D; G01D5/00; G01D5/12; G01D5/14; G01D5/20; G01D5/204; H03K17/972
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
145 words
A keyboard switch comprising a longitudinal housing, a toroidal magnetic core, means mounting said core in said housing so that the axis of said core is substantially perpendicular to the longitudinal axis of said housing, a pair of waferlike permanent magnets, a keystem carried in said housing for reciprocating movement along the longitudinal axis of said housing, said keystem being formed to have a pair of spaced-apart legs, each of said magnets mounted on one of said legs, said legs and magnets being arranged so that the opposed faces of said magnets are positioned in planes substantially parallel to the longitudinal axis of said housing and the axis of said core, said legs and magnets being further arranged so that said opposed faces are positioned substantially immediately adjacent to the periphery of said core in one longitudinal position of said keystem relative to said housing.
Claim 2
Dependent Claim
145 words
A keyboard switch comprising a longitudinal housing, a toroidal magnetic core, means mounting said core in said housing so that the axis of said core is substantially perpendicular to the longitudinal axis of said housing, a pair of waferlike permanent magnets, a keystem carried in said housing for reciprocating movement along the longitudinal axis of said housing, said keystem being formed to have a pair of spaced-apart legs, each of said magnets mounted on one of said legs, said legs and magnets being arranged so that the opposed faces of said magnets are positioned in planes substantially parallel to the longitudinal axis of said housing and the axis of said core, said legs and magnets being further arranged so that said opposed faces are positioned substantially immediately adjacent to the periphery of said core in one longitudinal position of said keystem relative to said housing.
Claim 3
Dependent Claim
26 words
A keyboard switch as defined in claim 1, wherein said magnets are formed to have a width substantially greater than the axial thickness of said core.
Claim 4
Dependent Claim
37 words
A keyboard switch as defined in claim 2, biasing means for biasing said keystem in said one longitudinal position, and said magnets being further formed to have a height substantially equal to the diameter of said core.
Claim 5
Dependent Claim
36 words
A keyboard switch as defined in claim 3, wherein the north pole of one of said magnets and the south pole of the other of said magnets is disposed adjacent to the periphery of said core.
Claim 6
Dependent Claim
21 words
A keyboard switch as defined in claim 4, wherein said magnetic core is made of a material exhibiting low magnetic remanence.
Claim 7
Dependent Claim
16 words
A keyboard switch as defined in claim 3, and further comprising a winding threading said core.
Claim 8
Dependent Claim
19 words
A keyboard switch as defined in claim 3, and further comprising drive-winding means and sense-winding means threading said core.
Claim 9
Dependent Claim
26 words
A keyboard switch as defined in claim 3, and said legs and the portion of said keystem interconnecting said legs being formed of a magnetic material.
Claim 10
Dependent Claim
51 words
A keyboard switch as defined in claim 1, wherein said housing is formed to have a recess therein extending from one side of said housing to the other along the axis of said core whereby a winding may be passed through said housing and said core in a substantially straight line.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-01-24 | 1975-07-26 | 1976-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-01-24 | 1979-07-26 | 1980-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-01-24 | 1983-07-26 | 1984-01-25 | $7700.00 | Window Closed / Lapsed |