US5138881A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Liquid level sensor including conductive plastic technology
Assignee: Spectrol Electronics Corp
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Filing: 1991-02-13
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Granted: 1992-08-18
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Expires: 2011-02-13
Abstract
Abstract A liquid level sensor for sensing liquid levels within a container is disclosed. The sensor includes a conductive plastic resistor and conductive plastic conductors deposited onto a thin polymer insulator. The conductive plastic resistor is a potentiometric resistive track which is electrically contacted at points along the length of the resistor by a contact assembly attached to a float. The polymer insulator is attached to a conductive support member or conductive strip disposed substantially vertically in the liquid. The float is disposed about the conductive strip. The contacts provide a short circuit between the resistive strip and conductive strip and thereby provide a resistive circuit connection analogous to the wiper of a potentiometer.
Inventors
- 👤 Richard E. Riley
- 👤 Thomas H. Brunjes
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 15:36
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/30; G01F23/64; G01F23/68; H; H01; H01C; H01C10/00; H01C10/30; H01C10/38; H01C10/40; H01C10/42
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
190 words
A liquid level sensor for providing a variable resistance corresponding to fluid level in a container, said sensor comprising: an elongated conductive support member having at least one elongated planar surface; an insulating film attached to and substantially covering said planar surface of said conductive member; a resistive strip having a first and a second end, said resistive strip attached to said insulating film, said resistive strip substantially aligned with the longitudinal axis of said conductive member; a first conductive strip attached to said insulator, said conductive strip disposed substantially in parallel with said resistive strip, said conductive strip having a length substantially equal to the length of said resistive strip, said first conductive strip electrically connected to said first end of said resistive strip; a second conductive strip attached to said insulator and electrically connected to said second end of said resistive strip; a float having a hole for axially receiving said conductive member wherein said float is positioned according to the liquid level in the container; and electrical contact means attached to said float for continuously establishing an electrical connection between said resistive strip and said conductive member.
Claim 2
Dependent Claim
190 words
A liquid level sensor for providing a variable resistance corresponding to fluid level in a container, said sensor comprising: an elongated conductive support member having at least one elongated planar surface; an insulating film attached to and substantially covering said planar surface of said conductive member; a resistive strip having a first and a second end, said resistive strip attached to said insulating film, said resistive strip substantially aligned with the longitudinal axis of said conductive member; a first conductive strip attached to said insulator, said conductive strip disposed substantially in parallel with said resistive strip, said conductive strip having a length substantially equal to the length of said resistive strip, said first conductive strip electrically connected to said first end of said resistive strip; a second conductive strip attached to said insulator and electrically connected to said second end of said resistive strip; a float having a hole for axially receiving said conductive member wherein said float is positioned according to the liquid level in the container; and electrical contact means attached to said float for continuously establishing an electrical connection between said resistive strip and said conductive member.
Claim 3
Dependent Claim
13 words
The sensor of claim 1 wherein said conductive member is a rectangular strip.
Claim 4
Dependent Claim
14 words
The sensor of claim 1 wherein said insulating film is a plastic polymer film.
Claim 5
Dependent Claim
25 words
The sensor of claim 3 wherein said resistive strip is a conductive plastic resistor and said first and second conductive strips are conductive plastic conductors.
Claim 6
Dependent Claim
16 words
The sensor of claim 4 wherein said float is made of a closed cell foam float.
Claim 7
Dependent Claim
13 words
The sensor of claim 5 wherein said conductive member is a rectangular strip.
Claim 8
Dependent Claim
23 words
The sensor of claim 6 wherein said resistive strip and said first and second conductive strips are screen printed onto said insulating film.
Claim 9
Dependent Claim
83 words
The sensor of claim 7 including a cylindrical housing for receiving said conductive strip and float therein, said sensor further including a top flange and a bottom flange attached to the open ends of said cylindrical housing, said top and bottom flange including means for fixedly receiving said conductive strip when said top and bottom flange are attached to said cylindrical housing, said top and bottom flanges including holes therein which enable fluid to enter and leave the interior of the cylindrical housing.
Claim 10
Dependent Claim
57 words
The sensor of claim 8 including a first connection terminal attached to said top flange and electrically connected to said first conductive strip, a second connection terminal attached to said top flange and electrically connected to said second conductive strip, and a third connection terminal attached to said top flange and electrically connected to said conductive member.
Claim 11
Dependent Claim
26 words
The sensor of claim 9 wherein said conductive member is aluminum, said insulating film is KAPTON polymer film, and said float is made of nitrile rubber.
Claim 12
Dependent Claim
189 words
A liquid level sensor for providing a variable resistance corresponding to fluid level in a container, said sensor comprising: a conductive rod having a first end and a second end; an insulating film attached to said conductive rod on the lateral surface of said rod; a resistive strip having a first and a second end, said resistive strip attached to said insulating film, said resistive strip substantially aligned with the longitudinal axis of said conductive rod; a first conductive strip attached to said insulator, said conductive strip disposed substantially in parallel with said resistive strip, said conductive strip having a length substantially equal to the length of said resistive strip, said first conductive strip electrically connected to said first end of said resistive strip; a second conductive strip attached to said insulator and electrically connected to said second end of said resistive strip; a float having a hole for axially receiving said conductive rod wherein said float is positioned according to the liquid level in the container; and electrical contact means attached to said float for continuously establishing an electrical connection between said resistive strip and said conductive rod.
Claim 13
Dependent Claim
189 words
A liquid level sensor for providing a variable resistance corresponding to fluid level in a container, said sensor comprising: a conductive rod having a first end and a second end; an insulating film attached to said conductive rod on the lateral surface of said rod; a resistive strip having a first and a second end, said resistive strip attached to said insulating film, said resistive strip substantially aligned with the longitudinal axis of said conductive rod; a first conductive strip attached to said insulator, said conductive strip disposed substantially in parallel with said resistive strip, said conductive strip having a length substantially equal to the length of said resistive strip, said first conductive strip electrically connected to said first end of said resistive strip; a second conductive strip attached to said insulator and electrically connected to said second end of said resistive strip; a float having a hole for axially receiving said conductive rod wherein said float is positioned according to the liquid level in the container; and electrical contact means attached to said float for continuously establishing an electrical connection between said resistive strip and said conductive rod.
Claim 14
Dependent Claim
12 words
The sensor of claim 11 wherein said rod has a rectangular cross-section.
Claim 15
Dependent Claim
26 words
The sensor of claim 12 wherein said resistive strip, said first conductive strip, and said second conductive strip are conductive plastic deposited onto said insulating film.
Claim 16
Dependent Claim
15 words
The sensor of claim 13 wherein said conductive plastic is screen-printed onto said insulating film.
Claim 17
Dependent Claim
16 words
The sensor of claim 13 wherein said conductive plastic is sputter deposited onto said insulating film.
Claim 18
Dependent Claim
39 words
The sensor of claim 13 including a first connection terminal electrically connected to said first conductive strip, a second connection terminal electrically connected to said second conductive strip, and a third connection terminal electrically connected to said conductive rod.
Claim 19
Dependent Claim
20 words
The sensor of claim 14 including a cylindrical housing, said conductive rod and said float disposed within said cylindrical housing.
Claim 20
Dependent Claim
13 words
The sensor of claim 17 wherein said insulating film is KAPTON polymer film.
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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) | 1995-08-18 | 1996-02-17 | 1996-08-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-08-18 | 2000-02-17 | 2000-08-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-08-18 | 2004-02-17 | 2004-08-18 | $7700.00 | Window Closed / Lapsed |