US3732503A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Proximity switch including variable frequency oscillator with ferrite control element
Assignee: Individual
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Filing: 1972-02-11
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Granted: 1973-05-08
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Expires: 1992-02-11
Abstract
Abstract A proximity switch is provided having an oscillator with a resonant circuit with a variable inductance. The output of the oscillator is fed through a low pass filter and rectifier to a switching circuit which is activated at a predetermined amplitude. The proximity switch is activated when a control body of non-magnetizable ferrite material is moved in close proximity to the inductor of the resonant circuit, thereby increasing the inductance and reducing the frequency of oscillation, and maintaining or increasing the amplitude of the output of the oscillator, the lower frequency and high amplitude signal being passed by the low pass filter and applied after rectification to activate the switch. The switch is not activated by electrically conductive materials because the frequency of the oscillator does not change and the amplitude of its output is damped, and it is not actuated by magnetic materials such as steel chips or permanent magnets because of high eddy current and hysteresis losses induced into the resonant circuit and damping of its output which fail to provide the output necessary to trigger the switch.
Inventors
- 👤 W Rapp
- 👤 W Albrecht
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 12:00
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/945; H03K17/95; H03K17/952; H03K17/9537; H03K17/9542; H03K17/9545; H03K17/9547
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
120 words
A proximity switch comprising a. an oscillator including a resonant circuit having a variable inductor, b. a control element of non-permanently magnetizable ferrite material movable to and away from the variable inductor of said resonant circuit, c. said control element of ferrite material when a predetermined distance from said inductor of said resonant circuit producing a changed output from said oscillator by increasing the inductance of said inductor, thereby decreasing the frequency of oscillation while maintaining or increasing the amplitude and voltage of the output of said oscillator, d. circuit means responsive to said changed output from said oscillator to produce a control signal, and e. switch means coupled to said circuit means operating in response to said control signal.
Claim 2
Dependent Claim
120 words
A proximity switch comprising a. an oscillator including a resonant circuit having a variable inductor, b. a control element of non-permanently magnetizable ferrite material movable to and away from the variable inductor of said resonant circuit, c. said control element of ferrite material when a predetermined distance from said inductor of said resonant circuit producing a changed output from said oscillator by increasing the inductance of said inductor, thereby decreasing the frequency of oscillation while maintaining or increasing the amplitude and voltage of the output of said oscillator, d. circuit means responsive to said changed output from said oscillator to produce a control signal, and e. switch means coupled to said circuit means operating in response to said control signal.
Claim 3
Dependent Claim
138 words
A proximity switch comprising a. an oscillator including a resonant circuit having a variable inductor, b. a control element of non-permanently magnetizable ferrite material movable to and away from the variable inductor of said resonant circuit, c. said control element of ferrite material when a predetermined distance from said inductor of said resonant circuit producing a changed output from said oscillator by increasing the inductance of said inductor, thereby decreasing the frequency of oscillation while maintaining or increasing the amplitude and voltage of the output of said oscillator, and D. circuit means responsive to said changed output from said oscillator to produce a control signal, said circuit means including a low-pass filter and a switch means, said low-pass filter passing a larger amplitude signal in response to said changed output from said oscillator for operating said switch means.
Claim 4
Dependent Claim
138 words
A proximity switch comprising a. an oscillator including a resonant circuit having a variable inductor, b. a control element of non-permanently magnetizable ferrite material movable to and away from the variable inductor of said resonant circuit, c. said control element of ferrite material when a predetermined distance from said inductor of said resonant circuit producing a changed output from said oscillator by increasing the inductance of said inductor, thereby decreasing the frequency of oscillation while maintaining or increasing the amplitude and voltage of the output of said oscillator, and D. circuit means responsive to said changed output from said oscillator to produce a control signal, said circuit means including a low-pass filter and a switch means, said low-pass filter passing a larger amplitude signal in response to said changed output from said oscillator for operating said switch means.
Claim 5
Dependent Claim
36 words
The proximity switch set forth in claim 2 wherein a rectifier means is connected between the output of said low-pass filter and the input of said switch means for rectifying the output of said low-pass filter.
Claim 6
Dependent Claim
36 words
The proximity switch set forth in claim 2 wherein said switch means operates on a predetermined amplitude signal which is applied when said ferrite control element is in a predetermined position with respect to said inductor.
Claim 7
Dependent Claim
57 words
The proximity switch set forth in claim 4 having a rectifier means connected between the output of said low-pass filter and the input of said switch means for rectifying the output of said low-pass filter, said switch means comprising a flip-flop circuit which changes state on the receipt of said predetermined amplitude signal from said rectifier means.
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) | 1976-05-07 | 1976-11-06 | 1977-05-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-07 | 1980-11-06 | 1981-05-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-07 | 1984-11-06 | 1985-05-08 | $7700.00 | Window Closed / Lapsed |