US3694804A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Coolant level detector for engine cooling system
Assignee: Thomas Electronics Ltd
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Filing: 1970-06-11
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Granted: 1972-09-26
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Expires: 1990-06-11
Abstract
Abstract In a liquid level detector for an engine cooling system an oscillator is arranged to apply a continuous output signal to a probe located in a liquid coolant reservoir presenting to the oscillator a variable electrical impedance according to the liquid level therein and a relaxation oscillator is operative in response to signals from said oscillator and arranged to actuate an indicator device giving intermittent visual and/or audible warning when the surface of the liquid coolant falls to below a predetermined level; a clamp circuit is arranged to inhibit operation of the relaxation oscillator when the surface of the liquid coolant is at or above the predetermined level and thereby improve the noise immunity of the detector.
Inventors
- 👤 Frederick Norman Hill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 11:22
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/241; G01F23/243; G01F23/244
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
196 words
A liquid level detector for detecting the departure of the surface of a liquid coolant in a reservoir of an engine cooling system from a predetermined level, comprising: a first detection element in the form of a probe arranged to extend into the reservoir, a second detection element arranged for operative connection to the reservoir, an electrical impedance determined by the liquid present between said first and second detection elements and which varies in magnitude according to the liquid level in said reservoir, a first oscillator connected to the first and second detection elements and responsive to said electrical impedance therebetween to produce a first output signal when said electrical impedance reaches a magnitude corresponding to the departure of said liquid to below a predetermined level, a relaxation oscillator responsive to the first output of said first oscillator by producing a second output signal, indicator means responsive to the second output signal of said relaxation oscillator by producing an intermittent indicating or warning, a clamp circuit operative between said impedance and said relaxation oscillator and arranged to prevent operation of the relaxation oscillator when the surface of the liquid is at or above said predetermined level.
Claim 2
Dependent Claim
196 words
A liquid level detector for detecting the departure of the surface of a liquid coolant in a reservoir of an engine cooling system from a predetermined level, comprising: a first detection element in the form of a probe arranged to extend into the reservoir, a second detection element arranged for operative connection to the reservoir, an electrical impedance determined by the liquid present between said first and second detection elements and which varies in magnitude according to the liquid level in said reservoir, a first oscillator connected to the first and second detection elements and responsive to said electrical impedance therebetween to produce a first output signal when said electrical impedance reaches a magnitude corresponding to the departure of said liquid to below a predetermined level, a relaxation oscillator responsive to the first output of said first oscillator by producing a second output signal, indicator means responsive to the second output signal of said relaxation oscillator by producing an intermittent indicating or warning, a clamp circuit operative between said impedance and said relaxation oscillator and arranged to prevent operation of the relaxation oscillator when the surface of the liquid is at or above said predetermined level.
Claim 3
Dependent Claim
18 words
A liquid level detector as claimed in claim 1 wherein said first oscillator includes two coupled air coils.
Claim 4
Dependent Claim
18 words
A liquid level detector according to claim 1 wherein said first oscillator includes two coupled ferrite cored coils.
Claim 5
Dependent Claim
16 words
A liquid level detector according to claim 2 wherein the relaxation oscillator includes a unijunction transistor.
Claim 6
Dependent Claim
173 words
An engine cooling system incorporating a first detection element in the form of a probe arranged to extend into the reservoir, a second detection element arranged for operative connection to the reservoir, an electrical impedance determined by the liquid present between said first and second detection elements and which varies in magnitude according to the liquid level in sail reservoir, a first oscillator connected to the first and second detection elements and responsive to said electrical impedance therebetween to produce a first output signal when said electrical impedance reaches a magnitude corresponding to the departure of said liquid to below a predetermined level, a relaxation oscillator responsive to the first output of said first oscillator by producing a second output signal, indicator means responsive to the second output siGnal of said relaxation oscillator by producing an intermittent indication or warning, a clamp circuit operative between said impedance and said relaxation oscillator and arranged to prevent operation of the relaxation oscillator when the surface of the liquid is at or above the predetermined level.
Claim 7
Dependent Claim
173 words
An engine cooling system incorporating a first detection element in the form of a probe arranged to extend into the reservoir, a second detection element arranged for operative connection to the reservoir, an electrical impedance determined by the liquid present between said first and second detection elements and which varies in magnitude according to the liquid level in sail reservoir, a first oscillator connected to the first and second detection elements and responsive to said electrical impedance therebetween to produce a first output signal when said electrical impedance reaches a magnitude corresponding to the departure of said liquid to below a predetermined level, a relaxation oscillator responsive to the first output of said first oscillator by producing a second output signal, indicator means responsive to the second output siGnal of said relaxation oscillator by producing an intermittent indication or warning, a clamp circuit operative between said impedance and said relaxation oscillator and arranged to prevent operation of the relaxation oscillator when the surface of the liquid is at or above the predetermined level.
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) | 1975-09-26 | 1976-03-27 | 1976-09-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-26 | 1980-03-27 | 1980-09-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-26 | 1984-03-27 | 1984-09-26 | $7700.00 | Window Closed / Lapsed |