US3922658A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fluid level monitor
Assignee: Bendix Corp
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Filing: 1974-12-04
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Granted: 1975-11-25
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Expires: 1994-12-04
Abstract
Abstract A means for monitoring the level of fluid in a container is comprised of a thick film heating device located, at least in part, in close proximity to a thick film thermistor device, both of which are disposed on a substrate. A detection device is included to detect circuit changes in response to heat flow into the thermistor device as would occur when fluid level varies.
Inventors
- 👤 Patrick D Harper
- 👤 Theodore L Knight
- 👤 Michael Slavin
- 👤 Ward A Ingels
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 23:44
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/246; G01F23/247; Y; Y10; Y10S; Y10S73/00; Y10S73/05
Claims Analysis
Total Claims: 18
Claim 1
Independent Claim
282 words
A fluid level monitor constructed in accordance with thick film techniques for monitoring the level of a fluid within a container, comprising: a substrate; first and second electrical terminals; an electrical latch; first and second thermistors connected in series across said first and second terminals, said first thermistor being disposed on said substrate and said second thermistor being disposed on said substrate remote from said first thermistor; electrical means connected between said first and second terminals including heater means having at least a first portion thereof disposed in relatively close proximity to said first thermistor and adapted to heat said first thermistor, said first and second thermistors being connected with said electrical means into an electrical bridge configuration having interior points, said electrical latch being responsive to the voltage across said interior points to close said latch; means for supporting and positioning said substrate within said container with said first thermistor close to the level of the fluid so that at least one of said first thermistors and said first portion of said heater is in thermal contact with the fluid when the level thereof is high whereby the voltage across said interior points is of a first value, and said first thermistor and said first portion of heat heater are out of thermal contact with the fluid when the level thereof is low whereby the voltage across said interior points is of a second value; a source of a first electrical voltage impressed across said first and second terminals; a source of a second electrical voltage; and, indicator means responsive to the state of said latch and connected in series with said latch across said source of a second electrical voltage.
Claim 2
Dependent Claim
282 words
A fluid level monitor constructed in accordance with thick film techniques for monitoring the level of a fluid within a container, comprising: a substrate; first and second electrical terminals; an electrical latch; first and second thermistors connected in series across said first and second terminals, said first thermistor being disposed on said substrate and said second thermistor being disposed on said substrate remote from said first thermistor; electrical means connected between said first and second terminals including heater means having at least a first portion thereof disposed in relatively close proximity to said first thermistor and adapted to heat said first thermistor, said first and second thermistors being connected with said electrical means into an electrical bridge configuration having interior points, said electrical latch being responsive to the voltage across said interior points to close said latch; means for supporting and positioning said substrate within said container with said first thermistor close to the level of the fluid so that at least one of said first thermistors and said first portion of said heater is in thermal contact with the fluid when the level thereof is high whereby the voltage across said interior points is of a first value, and said first thermistor and said first portion of heat heater are out of thermal contact with the fluid when the level thereof is low whereby the voltage across said interior points is of a second value; a source of a first electrical voltage impressed across said first and second terminals; a source of a second electrical voltage; and, indicator means responsive to the state of said latch and connected in series with said latch across said source of a second electrical voltage.
Claim 3
Dependent Claim
38 words
The monitor of claim 1 wherein said latch is connected across said first and second terminals, said source of a first electrical voltage comprising said indicator means connected in series with said source of a second electrical voltage.
Claim 4
Dependent Claim
59 words
The monitor of claim 1 wherein said electrical means comprises impedance means connected across said first and second terminals, one of said interior points being within said impedance means; and means responsive to the voltage across said points for controlling current flow in said heater, said latch being responsive to current flow in said heater to close said latch.
Claim 5
Dependent Claim
38 words
The monitor of claim 3 wherein said latch is connected across said first and second terminals, said source of a first electrical voltage comprising said indicator means connected in series with said source of a second electrical voltage.
Claim 6
Dependent Claim
31 words
The monitor of claim 4 wherein said second terminal comprises the return terminal of said source of a first electrical voltage, said means for supporting and positioning comprising said second terminal.
Claim 7
Dependent Claim
45 words
The monitor of claim 1 wherein said heater means includes a second portion serially connected with said first portion between said first and second terminals, said second portion being disposed in relatively close proximity to said second thermistor and adapted to heat said second thermistor.
Claim 8
Dependent Claim
38 words
The monitor of claim 6 wherein said latcH is connected across said first and second terminals, said source of a first electrical voltage comprising said indicator means connected in series with said source of a second electrical voltage.
Claim 9
Dependent Claim
31 words
The monitor of claim 7 wherein said second terminal comprises the return terminal of said source of a first electrical voltage, said means for supporting and positioning comprising said second terminal.
Claim 10
Dependent Claim
64 words
The monitor of claim 1 wherein said electrical means comprises first and second means having positive resistance temperature coefficients connected in series across said first and second terminals, one of said interior points being at the junction of said first and second means, and a third means having a negative resistance temperature coefficient connected in shunt across one of said first and second means.
Claim 11
Dependent Claim
134 words
A fluid level monitor probe comprising: a thin, flat, plate like electrically non-conductive substrate having a supporting surface, said substrate being relatively long and narrow; at least a first heater affixed to said supporting surface at one end of said substrate; a first thermistor affixed to said supporting surface in close proximity to said first heater; a second thermistor affixed to said supporting surface at an opposite end of said substrate, said substrate being adapted for cooperation with a fluid whose level is to be monitored so that at least a portion of said one end is immersed in said fluid and said opposite end is out of said fluid; and, electrically conductive tracks affixed to said supporting surface and adapted to provide electrical communication between said first and second thermistors and said heater.
Claim 12
Dependent Claim
134 words
A fluid level monitor probe comprising: a thin, flat, plate like electrically non-conductive substrate having a supporting surface, said substrate being relatively long and narrow; at least a first heater affixed to said supporting surface at one end of said substrate; a first thermistor affixed to said supporting surface in close proximity to said first heater; a second thermistor affixed to said supporting surface at an opposite end of said substrate, said substrate being adapted for cooperation with a fluid whose level is to be monitored so that at least a portion of said one end is immersed in said fluid and said opposite end is out of said fluid; and, electrically conductive tracks affixed to said supporting surface and adapted to provide electrical communication between said first and second thermistors and said heater.
Claim 13
Dependent Claim
37 words
The probe of claim 10 with a second heater affixed to said supporting surface at said opposite end and in close proximity to said second thermistor, said electrically conductive tracks providing electrical communication with said second heater.
Claim 14
Dependent Claim
29 words
The probe of claim 11 wherein said first and second heaters and said first and second thermistors are arranged with said electrically conductive tracks to form a bridge circuit.
Claim 15
Dependent Claim
29 words
The probe of claim 12 with means for sensing the voltage across interior points of said bridge circuit and also including means for impressing voltage across said bridge circuit.
Claim 16
Dependent Claim
58 words
The probe of claim 10 with further resistance means affixed to said supporting surface and cooperating with said first and second thermistors and said electrically conductive tracks to form a bridge circuit, the voltage across interior points of said bridge circuit comprising a first signal; and, means for controlling said first heater in response to said first signal.
Claim 17
Dependent Claim
212 words
A fluid level monitor constructed in accordance with thick film techniques for monitoring the level of a fluid within a container, comprising: a substrate; first and second electrical terminals; electrical means connected between said first and second electrical terminals including first and second thermistors, said first thermistor being disposed on said substrate and said second thermistor being disposed on said substrate remote from said first thermistor and heater means having at least a first portion thereof disposed in relatively close proximity to said first thermistor and adapted to heat said first thermistor, and wherein said substrate is adapted to be supported and positioned within said container with said first thermistor close to the level of the fluid so that at least one of said first thermistors and said first portion of said heater is in thermal contact with the fluid when the level thereof is high whereby the ratio of the resistance of said first thermistor with respect to the resistance of said second thermistor is a first value, and whereby the ratio of the resistance of said first thermistor with respect to the resistance of said second thermistor is a second value when said first thermistor and said first portion of said heater are out of thermal contact with the fluid.
Claim 18
Dependent Claim
212 words
A fluid level monitor constructed in accordance with thick film techniques for monitoring the level of a fluid within a container, comprising: a substrate; first and second electrical terminals; electrical means connected between said first and second electrical terminals including first and second thermistors, said first thermistor being disposed on said substrate and said second thermistor being disposed on said substrate remote from said first thermistor and heater means having at least a first portion thereof disposed in relatively close proximity to said first thermistor and adapted to heat said first thermistor, and wherein said substrate is adapted to be supported and positioned within said container with said first thermistor close to the level of the fluid so that at least one of said first thermistors and said first portion of said heater is in thermal contact with the fluid when the level thereof is high whereby the ratio of the resistance of said first thermistor with respect to the resistance of said second thermistor is a first value, and whereby the ratio of the resistance of said first thermistor with respect to the resistance of said second thermistor is a second value when said first thermistor and said first portion of said heater are out of thermal contact with the fluid.
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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) | 1978-11-24 | 1979-05-26 | 1979-11-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-11-24 | 1983-05-26 | 1983-11-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-11-24 | 1987-05-26 | 1987-11-25 | $7700.00 | Window Closed / Lapsed |