US3761736A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Proximity switches
Assignee: Godwin Warren Engineering Ltd
•
Filing: 1972-04-10
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Granted: 1973-09-25
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Expires: 1992-04-10
Abstract
Abstract A proximity switch, the sensing portion of which is an insulated electrode whose capacitance can be changed, for example by bringing one''s finger close to the electrode, to operate the switch, wherein the charge in capacitance is coupled into a bridge circuit which has a delayed self-balancing action, so that rapid changes in capacitance will operate the switch but long term slow changes in the capacitance will fail to operate the switch.
Inventors
- 👤 Edge G Malcolm
- 👤 P Lee
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:38
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/945; H03K17/955; H03K2217/00; H03K2217/94; H03K2217/96; H03K2217/9607; H03K2217/960735; H03K2217/96075; Y; Y10; Y10T; Y10T82/00; Y10T82/25; Y10T82/2572
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
189 words
An apparatus for responding to proximity of objects by behaving as a switch, comprising a bridge circuit having two bridge arms, supply means for supplying two alternating current signals, one to each of said arms, said two signals being of the same frequency but of opposite phase, sensing means including an insulated electrode connected to a first one of said bridge arms, said sensing means forming a capacitance with said insulated electrode, a phase-sensitive detector connected to sum the outputs of the two bridge arms, a variable reference capacitor connected to a second one of said bridge arms, control means responsive to said phase-sensitive detector and coupled to said variable capacitor for varying the capacitance of said variable capacitor in response to long-term slow changes in the capacitance of said sensing means so that the output of said detector remains balanced and for preventing rapid changes in the capacitance of said sensing means from balancing said bridge arms, said control means including delay circuit means connected to the output of said phase-sensitive detector and having an output for controlling the capacitance of said variable reference capacitor with a delay.
Claim 2
Independent Claim
189 words
An apparatus for responding to proximity of objects by behaving as a switch, comprising a bridge circuit having two bridge arms, supply means for supplying two alternating current signals, one to each of said arms, said two signals being of the same frequency but of opposite phase, sensing means including an insulated electrode connected to a first one of said bridge arms, said sensing means forming a capacitance with said insulated electrode, a phase-sensitive detector connected to sum the outputs of the two bridge arms, a variable reference capacitor connected to a second one of said bridge arms, control means responsive to said phase-sensitive detector and coupled to said variable capacitor for varying the capacitance of said variable capacitor in response to long-term slow changes in the capacitance of said sensing means so that the output of said detector remains balanced and for preventing rapid changes in the capacitance of said sensing means from balancing said bridge arms, said control means including delay circuit means connected to the output of said phase-sensitive detector and having an output for controlling the capacitance of said variable reference capacitor with a delay.
Claim 3
Dependent Claim
18 words
A switch as in claim 1, wherein said sensing means includes a grounded guard ring surrounding said electrode.
Claim 4
Dependent Claim
30 words
An aPparatus as in claim 1, wherein said variable reference capacitor is connected to ground and said sensing means forms its capacitance with said electrode between said electrode and ground.
Claim 5
Dependent Claim
16 words
A apparatus as claimed in claim 1, wherein said reference capacitance includes a voltage variable capacitor.
Claim 6
Independent Claim
30 words
A apparatus as claimed in any one of claims 1, wherein a number of electrodes are provided on a single panel, each electrode being provided with a separate bridge circuit.
Claim 7
Dependent Claim
17 words
A apparatus as claimed in claim 5, wherein each electrode is surrounded by an grounded guard ring.
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) | 1976-09-24 | 1977-03-26 | 1977-09-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-09-24 | 1981-03-26 | 1981-09-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-09-24 | 1985-03-26 | 1985-09-25 | $7700.00 | Window Closed / Lapsed |