US4529968A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Touch sensitive liquid crystal switch
Assignee: UK Secretary of State for Defence
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Filing: 1982-11-10
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Granted: 1985-07-16
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Expires: 2002-11-10
Abstract
Abstract A touch sensitive switch with a liquid crystal cell and a circuit for measuring capacitive changes when the cell is deformed by touch. The cell has a layer of a liquid crystal material between slides bearing electrodes. Capacitive changes are detected for example by a comparator or by a bridge circuit which includes one or more cells. Touching one cell unbalances the bridge. The area of cell that is touched may be coincident with or separate from a display area. For some types of cells extra sensitivity is achieved by maintaining a voltage across the cell between a critical and saturation value.
Inventors
- 👤 Cyril Hilsum
- 👤 Edward P. Raynes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 07:12
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/96; H03K17/962
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
82 words
A touch sensitive switch comprising: a liquid crystal cell formed by a layer of liquid crystal material contained between two electrode bearing slides, means for applying a voltage to the electrodes above a threshold value at which liquid crystal molecules begin to rotate under the effect of the electric field caused by the applied voltage, means for detecting a change in cell capacitance between said electrodes when the cell is deformed, and means for producing a signal indicating said detected capacitance change.
Claim 2
Dependent Claim
82 words
A touch sensitive switch comprising: a liquid crystal cell formed by a layer of liquid crystal material contained between two electrode bearing slides, means for applying a voltage to the electrodes above a threshold value at which liquid crystal molecules begin to rotate under the effect of the electric field caused by the applied voltage, means for detecting a change in cell capacitance between said electrodes when the cell is deformed, and means for producing a signal indicating said detected capacitance change.
Claim 3
Dependent Claim
24 words
The switch according to claim 1 wherein the cell is arranged to change displayed information in at least a part of the cell area.
Claim 4
Dependent Claim
23 words
The switch according to claim 2 wherein that part of the cell displaying information is arranged to be deformable by an operators touch.
Claim 5
Dependent Claim
24 words
The switch according to claim 2 wherein that part of the cell displaying information is separate from that part deformable by an operators touch.
Claim 6
Dependent Claim
35 words
The switch according to claim 1 wherein the means for detecting a change in capacitance includes a balanced bridge circuit which is unbalanced on deformation of the cell which forms a part of the bridge.
Claim 7
Dependent Claim
17 words
The switch according to claim 5 wherein a plurality of cells are connected into the bridge circuit.
Claim 8
Dependent Claim
15 words
The switch according to claim 1 wherein the liquid crystal material is a nematic material.
Claim 9
Dependent Claim
15 words
The switch according to claim 1 wherein the liquid crystal material is a cholesteric material.
Claim 10
Dependent Claim
19 words
The switch according to claim 1 wherein an amount of a dye is dissolved in the liquid crystal material.
Claim 11
Dependent Claim
27 words
The switch according to claim 1 wherein the facing surfaces of the slides are treated to align contacting liquid crystal molecules at an angle to the surfaces.
Claim 12
Dependent Claim
47 words
The switch according to claim 1 wherein the means for detecting a change in capacitance includes means for supplying a voltage across the cell and a reference capacitor connected together in series, and a comparator for comparing the voltage developed across the cell with a reference voltage.
Claim 13
Dependent Claim
71 words
A touch sensitive switch comprising: a liquid crystal cell formed by a layer of liquid crystal material contained between two electrode bearing slides, the slides being surface treated to give a molecule tilt above 10° to the liquid crystal molecules at the slide surface, means for detecting a change in cell capacitance between said electrodes when the cell is deformed, and means for producing a signal indicating said detected capacitance change.
Claim 14
Dependent Claim
71 words
A touch sensitive switch comprising: a liquid crystal cell formed by a layer of liquid crystal material contained between two electrode bearing slides, the slides being surface treated to give a molecule tilt above 10° to the liquid crystal molecules at the slide surface, means for detecting a change in cell capacitance between said electrodes when the cell is deformed, and means for producing a signal indicating said detected capacitance change.
References Cited (Backward Citations)
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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) | 1988-07-15 | 1989-01-14 | 1989-07-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-07-15 | 1993-01-14 | 1993-07-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-07-15 | 1997-01-14 | 1997-07-16 | $7700.00 | Window Closed / Lapsed |