Patent US3019491A successfully refreshed from Google Patents.
Patent US3723885A successfully refreshed from Google Patents.
US3723885A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Capacitance proximity switch
Assignee: Individual
•
Filing: 1971-05-03
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Granted: 1973-03-27
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Expires: 1991-05-03
Abstract
Abstract The invention refers to a capacitance proximity switch which is more reliable than known devices. This is achieved by using a circuit which makes it possible to use digital circuits instead of linear amplifiers. The device comprises a square wave oscillator, a pulse stretcher fed by the oscillator using the capacitance between two electrically conducting bodies as at least part of the timing capacitance, means for detecting the change of mark-space ratio due to change of capacitance between the said two bodies and the means to operate a switch when the mark-space ratio differs from a predetermined value. The change of capacitance may be caused by changing the distance between the said two bodies or by approaching one or both of the bodies by a third body which latter may be a conductor or an insulator.
Inventors
- 👤 W Urmenyi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 07:09
CPC Classifications
G; G08; G08B; G08B13/00; G08B13/22; G08B13/26; H; H03; H03K; H03K17/00; H03K17/94; H03K17/96; H03K17/962
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
83 words
A capacitance proximity switch comprising a square wave oscillator, a pulse stretcher, means to connect the oscillator to the pulse stretcher, two electrically conducting bodies having an electric capacitance between them, means to connect said capacitance to form at least part of a timing capacitance which determines the mark-space ratio, means for detecting the change of mark-space ratio due to change of capacitance between the said two bodies and means to operate a switch when the mark-space ratio differs from a predetermined value.
Claim 2
Dependent Claim
83 words
A capacitance proximity switch comprising a square wave oscillator, a pulse stretcher, means to connect the oscillator to the pulse stretcher, two electrically conducting bodies having an electric capacitance between them, means to connect said capacitance to form at least part of a timing capacitance which determines the mark-space ratio, means for detecting the change of mark-space ratio due to change of capacitance between the said two bodies and means to operate a switch when the mark-space ratio differs from a predetermined value.
Claim 3
Dependent Claim
42 words
A capacitance proximity switch as claimed in claim 1 comprising also means to provide negative feed-back from the said means for detecting the change of mark-space ratio, the said negative feed-back, comprising a time-delay circuit, counteracting the change in the mark-space ratio.
Claim 4
Dependent Claim
32 words
A capacitance proximity switch as claimed in claim 1 comprising also means to provide negative feed-back from the said means for detecting the change of mark-space ratio to the said pulse stretcher.
Claim 5
Dependent Claim
45 words
A capacitance proximity switch as claimed in claim 1 comprising also means to provide negative feed-back from the said means for detecting the change of mark-space ratio, the said negative feed-back, comprising a time-delay circuit and an amplifier, counteracting the change in the mark-space ratio.
Claim 6
Dependent Claim
50 words
A capacitance proximity switch as claimed in claim 1 comprising also means to provide negative feed-back from the said means for detecting the change of mark-space ratio, the said negative feed-back comprising a time-delay circuit, an amplifier and a constant current generator, said constant current generator charging the timing capacitor.
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) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |