Patent US3870948A successfully refreshed from Google Patents.
US3870948A
Expired / Lapsed
US
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Proximity circuit with active device feedback
Assignee: Acme Cleveland Corp
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Filing: 1972-09-05
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Granted: 1975-03-11
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Expires: 1992-09-05
Abstract
Abstract A proximity switch circuit is disclosed which is responsive to the distance between a proximity probe and a conductive or inductive target. An amplifier is connected as an oscillator in a bridge circuit with the probe as one arm of the bridge and variations of distance between the probe and the target change the balance point of the bridge to change oscillation output. If the target is close, the oscillator will tend to cease and this is detected by an auxiliary detector to partly turn on an auxiliary energy pump which sustains oscillation output of the amplifier. This output is fed to a window detector which determines if the output is between lower and upper threshold values, and if it is, then there is an output from an output circuit. If the detector circuit determines that the amplifier output is below the lower threshold or greater than the upper threshold, then there is no output. This establishes a fail-safe operating condition by terminating the output should the oscillator cease to function for reasons such as short-circuiting or open-circuiting of the proximity probe.
Inventors
- 👤 Frederick R Holt
- 👤 Noah Flueckiger
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:20
CPC Classifications
H; H03; H03K; H03K17/00; H03K17/94; H03K17/945; H03K17/95; H03K17/952; H03K17/9537; H03K17/9542; H03K17/9547; H03K17/9502; H03K2217/00; H03K2217/94; H03K2217/945; H03K2217/95; H03K2217/956
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
117 words
A proximity switch circuit comprising in combination, a main amplifier having an output and an input, a proximity probe, feedback means connecting said amplifier output to said amplifier input, means connecting said probe as part of said feedback means to produce a signal at said input of said amplifier which is variable in accordance with the distance from said probe to a conductive target, an auxiliary alternating current amplifier, means connecting said auxiliary amplifier as part of said feedback means to vary said main amplifier alternating current input, and detector means connected to detect reduced output of said main amplifier and connected to control said auxiliary amplifier to increase the alternating current output of said main amplifier.
Claim 2
Dependent Claim
117 words
A proximity switch circuit comprising in combination, a main amplifier having an output and an input, a proximity probe, feedback means connecting said amplifier output to said amplifier input, means connecting said probe as part of said feedback means to produce a signal at said input of said amplifier which is variable in accordance with the distance from said probe to a conductive target, an auxiliary alternating current amplifier, means connecting said auxiliary amplifier as part of said feedback means to vary said main amplifier alternating current input, and detector means connected to detect reduced output of said main amplifier and connected to control said auxiliary amplifier to increase the alternating current output of said main amplifier.
Claim 3
Dependent Claim
117 words
A proximity switch circuit comprising in combination, a main amplifier having an output and an input, a proximity probe, feedback means connecting said amplifier output to said amplifier input, means connecting said probe as part of said feedback means to produce a signal at said input of said amplifier which is variable in accordance with the distance from said probe to a conductive target, an auxiliary alternating current amplifier, means connecting said auxiliary amplifier as part of said feedback means to vary said main amplifier alternating current input, and detector means connected to detect reduced output of said main amplifier and connected to control said auxiliary amplifier to increase the alternating current output of said main amplifier.
Claim 4
Dependent Claim
117 words
A proximity switch circuit comprising in combination, a main amplifier having an output and an input, a proximity probe, feedback means connecting said amplifier output to said amplifier input, means connecting said probe as part of said feedback means to produce a signal at said input of said amplifier which is variable in accordance with the distance from said probe to a conductive target, an auxiliary alternating current amplifier, means connecting said auxiliary amplifier as part of said feedback means to vary said main amplifier alternating current input, and detector means connected to detect reduced output of said main amplifier and connected to control said auxiliary amplifier to increase the alternating current output of said main amplifier.
Claim 5
Dependent Claim
37 words
A proximity switch circuit as set forth in claim 1, wherein said feedback means includes a bridge circuit having arms and an input and an output, and means connecting said bridge output to said main amplifier input.
Claim 6
Dependent Claim
36 words
A proximity switch circuit as set forth in claim 1, including inductive and capacitive means connected to be resonant at a given frequency, and means connecting said probe as part of said inductive and capacitive means.
Claim 7
Dependent Claim
28 words
A proximity switch circuit as set forth in claim 3, wherein said probe has a variable reactance as a part of one of said inductive and capacitive means.
Claim 8
Dependent Claim
31 words
A proximity switch circuit as set forth in claim 1, wherein said feedback means includes negative feedback means and positive feedback means each connected to the input of said main amplifier.
Claim 9
Dependent Claim
49 words
A proximity switch circuit as set forth in claim 5, wherein said feedback means includes a bridge circuit having four arms, means connecting said negative feedback means as two arms of said bridge circuit, and means connecting said positive feedback means as two remaining arms of said bridge circuit.
Claim 10
Dependent Claim
28 words
A proximity switch circuit as set forth in claim 1, wherein said feedback means includes positive feedback means, and said probe being connected in said positive feedback means.
Claim 11
Dependent Claim
29 words
A proximity switch circuit as set forth in claim 1, wherein said feedback means includes positive feedback means, and said auxiliary amplifier being connected in said positive feedback means.
Claim 12
Dependent Claim
30 words
A proximity switch circuit as set forth in claim 1, wherein said auxiliary amplifier has an output connected to said probe and has an input controlled by said detector means.
Claim 13
Dependent Claim
58 words
A proximity switch circuit as set forth in claim 1, including an output circuit connected to the output of said detector means, and bias means setting a threshold operating condition of said detector means to establish said detector means sensitive to outputs of said main amplifier less than said threshold to establish an output from said output circuit.
Claim 14
Dependent Claim
33 words
A proximity switch as set forth in claim 10, wherein said bias means establishes termination of the output from said output circuit upon output of said main amplifier being greater than said threshold.
Claim 15
Dependent Claim
92 words
A proximity switch as set forth in claim 1, including an output circuit connected to the output of said detector means, and bias means setting upper and lower threshold operating conditions of said detector means to establish said detector means sensitive to small outputs of said main amplifier between said upper and lower thresholds to establish an output from said output circuit and to establish termination of the output from said output circuit upon output of said main amplifier being either less than said lower threshold or greater than said upper threshold.
Claim 16
Dependent Claim
52 words
A proximity switch circuit as set forth in claim 12, wherein said feedback means includes negative and positive feedback means, and said probe being connected in said positive feedback means to establish oscillation of said main amplifier with a conductive target spaced from said probe a distance greater than a trip point.
Claim 17
Dependent Claim
32 words
A proximity switch circuit as set forth in claim 13, including means to vary the trip point at which there is a change detected by said detector means at said upper threshold.
Claim 18
Dependent Claim
90 words
A proximity switch as set forth in claim 1, wherein said detector means includes an auxiliary detector and first and second detectors, means connecting said auxiliary detector to control said auxiliary amplifier, bias means setting a lower threshold operating condition for said first detector and an upper threshold operating condition for said second detector, an output circuit connected to the output of said first and second detectors, and said lower and upper threshold operating conditions establishing a window with an output from said output circuit in accordance with said window.
Claim 19
Dependent Claim
41 words
A proximity switch as set forth in claim 15, wherein said lower and upper threshold operating conditions establish termination of an output from said output circuit for main amplifier outputs less than said lower threshold and greater than said upper threshold.
Claim 20
Dependent Claim
21 words
A proximity switch as set forth in claim 1, including an alternating and a direct current input to said main amplifier.
Claim 21
Dependent Claim
19 words
A proximity switch as set forth in claim 1, including in said feedback means an alternating current negative feedback.
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) | 1978-03-10 | 1978-09-09 | 1979-03-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-03-10 | 1982-09-09 | 1983-03-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-03-10 | 1986-09-09 | 1987-03-11 | $7700.00 | Window Closed / Lapsed |