US3631440A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Liquid level detector
Assignee: Individual
•
Filing: 1969-07-07
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Granted: 1971-12-28
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Expires: 1989-07-07
Abstract
Abstract A liquid level detector comprising a voltage-divider network, including a thermistor, connected between the terminals of a battery so that the potential at the voltage-divider output varies as a function of the resistance of the thermistor. The voltage-divider output is connected to the input of a voltagesensitive switching circuit which is connected via a Zener diode to one of the battery terminals whereby the Zener diode provides a reference voltage level which is independent of current and battery voltage fluctuations. The voltage-sensitive switching circuit has two stable states and is either in one state or the other depending upon whether the potential at the voltage-divider output is above or below the reference level provided by the Zener diode. When the potential at the voltage-divider output indicates that the thermistor is out of a good heat conductor such as a liquid, the switching circuit closes a series circuit between the battery and a lamp so that the lamp provides a visual indication of the low liquid level condition. According to a preferred embodiment of the invention, the reference voltage level provided by the Zener diode has first and second discrete, controllable values depending upon whether the potential at the voltage-divider output is greater or less than the reference level provided by the Zener diode to permit independent control of the activation and deactivation of the lamp.
Inventors
- 👤 Arnie L Cliffgard
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 14:51
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/246; G01F23/247
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
211 words
A liquid level detector for determining when the level of liquid in a container goes below a predetermined level, said detector being adapted for use with a voltage supply which provides first and second points of reference potential, comprising: a resistor and a thermistor connected in series betweEn said first and second points of reference potential, said thermistor adapted to be positioned in said container at said predetermined level; means operatively connected to and energized by said voltage supply for providing a third point of reference potential which is substantially independent of fluctuations of said voltage supply, said third point of reference potential having first and second discrete, controllable values depending upon whether the voltage at said junction is greater or less than said third point of reference potential; voltage-sensitive switching means operatively coupled between the junction between said resistor and said thermistor and said third point of reference potential for comparing the voltage at said junction with said third point of reference potential; and indicator means for indicating whether said liquid level is above or below said predetermined level, said switching means being operative to activate or deactivate said indicator means depending upon whether the voltage at said junction is greater or less than said third point of reference potential.
Claim 2
Dependent Claim
211 words
A liquid level detector for determining when the level of liquid in a container goes below a predetermined level, said detector being adapted for use with a voltage supply which provides first and second points of reference potential, comprising: a resistor and a thermistor connected in series betweEn said first and second points of reference potential, said thermistor adapted to be positioned in said container at said predetermined level; means operatively connected to and energized by said voltage supply for providing a third point of reference potential which is substantially independent of fluctuations of said voltage supply, said third point of reference potential having first and second discrete, controllable values depending upon whether the voltage at said junction is greater or less than said third point of reference potential; voltage-sensitive switching means operatively coupled between the junction between said resistor and said thermistor and said third point of reference potential for comparing the voltage at said junction with said third point of reference potential; and indicator means for indicating whether said liquid level is above or below said predetermined level, said switching means being operative to activate or deactivate said indicator means depending upon whether the voltage at said junction is greater or less than said third point of reference potential.
Claim 3
Dependent Claim
71 words
A liquid level detector according to claim 1, wherein said means providing a third point of reference potential comprises; a Zener diode, one end of said Zener diode being connected to said second point of reference potential; and a second resistor, one end of said second resistor being connected to the other end of said Zener diode, the other end of said second resistor providing said third point of reference potential.
Claim 4
Dependent Claim
117 words
A liquid level detector according to claim 2 wherein said voltage sensitive switching means comprises: first and second transistors having base, collectors, and emitters, the emitter of said first transistor being operatively connected to said other end of said second resistor, the base of said first transistor being connected to said junction; a third resistor, said third resistor being connected between said other end of said second resistor and the emitter of said second transistor; and a fourth resistor, said fourth resistor being connected between said first point of reference potential and the collector of said first transistor and the base of said second transistor, the collector of said second transistor being connected to said indicator means.
Claim 5
Dependent Claim
80 words
A liquid level detector according to claim 1 wherein said voltage-sensitive switching means has first and second stable states, said voltage-sensitive switching means changing to said first stable state when the voltage at said junction exceeds the first value of the potential at said third point of reference potential, said voltage-sensitive switching means changing to said second stable state when the voltage at said junction goes below the second value of the potential at said third point of reference potential.
Claim 6
Dependent Claim
38 words
A liquid level detector according to claim 4 wherein said indicator means is deactivated when said voltage-sensitive switching means is in said first stable state and is activated when said switching means is in said second stable state.
Claim 7
Dependent Claim
371 words
A liquid level detector for determining when the level of liquid in a container goes below a predetermined level, said detector being adapted for use with a voltage supply which provides first and second points of reference potential, comprising: a first resistor and a thermistor connected in series between said first and second points of reference potential, said thermistor adapted to be positioned in said container at said predetermined level; a Zener diode, one end of said Zener diode being connected to said second point of reference potential; a second resistor, one end of said second resistor being connected to the other end of said Zener diode, the other end of said second resistor providing a third point of reference potential which is substantially independent of fluctuations of said voltage supply; voltage-sensitive switching means operatively coupled between the junction between said first resistor and thermistor and said third point of reference potential or comparing the voltage at said junction with said third point of reference potential, said voltage-sensitive switching means comprising: first and second transistors having bases, collectors, and emitters, the emitter of said first transistor being connected to said third point of reference potential; a third resistor, said third resistor being connected between said first point of reference potential and the collector of said first transistor and the base of said second transistor; a fourth resistor connected between said junction and the base of said first transistor; a fifth resistor connected between the emitter of said second transistor and said third point of reference potential, said third and fifth resistors having different values whereby the current through said second resistor changes depending upon whether said first transistor or said second transistor is conducting, the value of said second resistor being small compared to the values of said third and fifth resistors; and a capacitor connected between the collector and the base of said first transistor; and indicator means connected to collector of said second transistor for indicating whether said liquid level is above or below said predetermined level, said voltage-sensitive switching means being operative to activate or deactivate said indicator means depending upon whether the voltage at said junction is greater or less then said third point of reference potential.
Claim 8
Dependent Claim
371 words
A liquid level detector for determining when the level of liquid in a container goes below a predetermined level, said detector being adapted for use with a voltage supply which provides first and second points of reference potential, comprising: a first resistor and a thermistor connected in series between said first and second points of reference potential, said thermistor adapted to be positioned in said container at said predetermined level; a Zener diode, one end of said Zener diode being connected to said second point of reference potential; a second resistor, one end of said second resistor being connected to the other end of said Zener diode, the other end of said second resistor providing a third point of reference potential which is substantially independent of fluctuations of said voltage supply; voltage-sensitive switching means operatively coupled between the junction between said first resistor and thermistor and said third point of reference potential or comparing the voltage at said junction with said third point of reference potential, said voltage-sensitive switching means comprising: first and second transistors having bases, collectors, and emitters, the emitter of said first transistor being connected to said third point of reference potential; a third resistor, said third resistor being connected between said first point of reference potential and the collector of said first transistor and the base of said second transistor; a fourth resistor connected between said junction and the base of said first transistor; a fifth resistor connected between the emitter of said second transistor and said third point of reference potential, said third and fifth resistors having different values whereby the current through said second resistor changes depending upon whether said first transistor or said second transistor is conducting, the value of said second resistor being small compared to the values of said third and fifth resistors; and a capacitor connected between the collector and the base of said first transistor; and indicator means connected to collector of said second transistor for indicating whether said liquid level is above or below said predetermined level, said voltage-sensitive switching means being operative to activate or deactivate said indicator means depending upon whether the voltage at said junction is greater or less then said third point of reference potential.
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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) | 1974-12-27 | 1975-06-28 | 1975-12-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-27 | 1979-06-28 | 1979-12-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-27 | 1983-06-28 | 1983-12-28 | $7700.00 | Window Closed / Lapsed |