Patent US3689883A successfully refreshed from Google Patents.
US3689883A
Expired / Lapsed
US
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Liquid level detector
Assignee: ZF International UK Ltd
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Filing: 1970-08-14
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Granted: 1972-09-05
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Expires: 1990-08-14
Abstract
Abstract A liquid level detection circuit for use in a road vehicle has an oscillator which functions with a plurality of separate liquid containers, each incorporating a probe immersed in the liquid, the level in any of the containers of which is to be detected. When the liquid level falls below a predetermined level, the resistance of the probe changes with a result that the oscillator ceases to operate. A warning device is employed which is held inoperative only when the oscillator is operating.
Inventors
- 👤 William Frank Hill
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 04:50
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/241; G01F23/243; G01F23/244
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
222 words
A liquid level detector for detecting liquid level in a plurality of independent containers and actuating a warning device if the liquid level in any of the containers falls below a predetermined level, comprising in combination: a plurality of liquid level probe means each disposed in one of said containers and displaying an increased electrical resistance if the liquid level in a respective container falls below a predetermined level; an oscillator means having a control input and an output; connecting means to connect said plurality of liquid level probes in parallel to said control input of said oscillator means; a warning device to indicate a low liquid level in any of said containers; a semiconducting device connected to said warning device and a power source, and having a control input point; and means connecting said control input point of said semiconducting device to the output of said oscillator means, whereby said oscillator means is maintained operative normally and said warning device is not actuated, but, upon the liquid in any of said plurality of containers falling below a predetermined level, a changed control voltage from a corresponding probe is supplied to said oscillator to interrupt the functioning thereof so that said semiconducting device is rendered conductive to actuate said warning device to indicate a low liquid level in one of said containers.
Claim 2
Dependent Claim
222 words
A liquid level detector for detecting liquid level in a plurality of independent containers and actuating a warning device if the liquid level in any of the containers falls below a predetermined level, comprising in combination: a plurality of liquid level probe means each disposed in one of said containers and displaying an increased electrical resistance if the liquid level in a respective container falls below a predetermined level; an oscillator means having a control input and an output; connecting means to connect said plurality of liquid level probes in parallel to said control input of said oscillator means; a warning device to indicate a low liquid level in any of said containers; a semiconducting device connected to said warning device and a power source, and having a control input point; and means connecting said control input point of said semiconducting device to the output of said oscillator means, whereby said oscillator means is maintained operative normally and said warning device is not actuated, but, upon the liquid in any of said plurality of containers falling below a predetermined level, a changed control voltage from a corresponding probe is supplied to said oscillator to interrupt the functioning thereof so that said semiconducting device is rendered conductive to actuate said warning device to indicate a low liquid level in one of said containers.
Claim 3
Dependent Claim
70 words
The liquid level detector as claimed in claim 1 in which said semiconducting device is a transistor with its emitter connected to one terminal of the power source, its collector connected through said warning device to the other terminal of the power source and wherein only pulses of a selected polarity from the output of said oscillator means are applied to the base of said transistor through a diode circuit.
Claim 4
Dependent Claim
119 words
The liquid level detector as claimed in claim 1 in which said semiconducting device is a transistor with its emitter connected to a positive terminal of said power source and its collector connected to the negative terminal of said power source through said warning device, and, negative pulses of the output of said oscillator means are connected to the base of said transistor through a diode circuit, the detector including a capacitor connected between the base of the transistor and the negative terminal of the power source so as to be charged with a negative potential to maintain the base of said transistor negative with respect to its emitter thereby rendering the transistor nonconductive when the oscillator is functioning.
Claim 5
Dependent Claim
26 words
The liquid level detector as claimed in claim 3 which includes a capacitance connected in series with each of said plurality of liquid level probe means.
Claim 6
Dependent Claim
26 words
The liquid level detector as claimed in claim 3 wherein resistances are included in said connecting means which connect said plurality of liquid level probe 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) | 1975-09-05 | 1976-03-06 | 1976-09-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-09-05 | 1980-03-06 | 1980-09-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-09-05 | 1984-03-06 | 1984-09-05 | $7700.00 | Window Closed / Lapsed |