US3846776A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Liquid level sensor
Assignee: TE Connectivity Corp
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Filing: 1973-04-16
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Granted: 1974-11-05
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Expires: 1993-04-16
Abstract
Abstract A sensor for detecting the presence of a heat conducting medium above a predetermined level in a container includes an electrical resistance element and a polyconductor having a predetermined transition temperature point selected at a temperature above the temperature to which the heat conducting medium is normally subjected. The polyconductor is thermally connected to the resistance element and that element has a predetermined resistance value selected to dissipate heat produced therein to the heat conducting medium at a temperature below the transition temperature of the polyconductor when immersed in the heat conducting medium, and to heat the polyconductor, in the absence of the heat conducting medium, to a temperature above the transition temperature whereby the polyconductor becomes conductive. In one embodiment of the invention the polyconductor is connected to a signal device which produces a signal when the polyconductor becomes conductive in this manner.
Inventors
- 👤 D Kahn
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 15:30
CPC Classifications
G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/246; G01F23/247
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
122 words
A device, adapted to be connected to a source of current, for detecting the presence or absence of a heat conducting medium, said device comprising an electrical resistance element and a polyconductor having a predetermined transition temperature selected at a temperature above the temperaTure to which said heat conducting medium is normally subjected, said polyconductor being thermally connected to said resistance element and said resistance element having a predetermined resistance value selected to dissipate heat to said heat conducting medium at a temperature below the transition temperature of said polyconductor when surrounded by said heat conducting medium and to heat said polyconductor to a temperature above said transition temperature, in the absence of said heat conducting medium, whereby said polyconductor becomes conductive.
Claim 2
Independent Claim
122 words
A device, adapted to be connected to a source of current, for detecting the presence or absence of a heat conducting medium, said device comprising an electrical resistance element and a polyconductor having a predetermined transition temperature selected at a temperature above the temperaTure to which said heat conducting medium is normally subjected, said polyconductor being thermally connected to said resistance element and said resistance element having a predetermined resistance value selected to dissipate heat to said heat conducting medium at a temperature below the transition temperature of said polyconductor when surrounded by said heat conducting medium and to heat said polyconductor to a temperature above said transition temperature, in the absence of said heat conducting medium, whereby said polyconductor becomes conductive.
Claim 3
Dependent Claim
24 words
The device as defined in claim 1 including signal means operatively connected to said polyconductor for producing a signal when said polyconductor becomes conductive.
Claim 4
Independent Claim
167 words
A device for detecting a drop in the liquid level in a container below a predetermined level, said device being adapted to be connected to a source of electrical current and comprising an electrical resistance element adapted to be mounted in said container at said predetermined level, a polyconductor having a predetermined transition temperature selected at a temperature above the temperature to which liquid in said container is normally subjected, said polyconductor being thermally connected to said resistance element; said resistance element having a predetermined resistance value selected to dissipate heat produced therein by said current to said liquid, when immersed therein, at a rate which maintains the temperature of said element and polyconductor below said transition temperature and to heat said polyconductor to a temperature above said transition temperature when the level of said liquid falls below said predetermined level, exposing said element, whereby said polyconductor becomes electrically conductive; and signal means electrically connected to said polyconductor for producing a signal when said polyconductor becomes conductive.
Claim 5
Independent Claim
167 words
A device for detecting a drop in the liquid level in a container below a predetermined level, said device being adapted to be connected to a source of electrical current and comprising an electrical resistance element adapted to be mounted in said container at said predetermined level, a polyconductor having a predetermined transition temperature selected at a temperature above the temperature to which liquid in said container is normally subjected, said polyconductor being thermally connected to said resistance element; said resistance element having a predetermined resistance value selected to dissipate heat produced therein by said current to said liquid, when immersed therein, at a rate which maintains the temperature of said element and polyconductor below said transition temperature and to heat said polyconductor to a temperature above said transition temperature when the level of said liquid falls below said predetermined level, exposing said element, whereby said polyconductor becomes electrically conductive; and signal means electrically connected to said polyconductor for producing a signal when said polyconductor becomes conductive.
Claim 6
Dependent Claim
28 words
The device as defined in claim 3 wherein said liquid in automobile brake fluid, said container is a master brake cylinder, and said transition temperature is 330* F.
Claim 7
Dependent Claim
57 words
The device as defined in claim 3 wherein said transition temperature is 330* F and said resistance value of said element is selected to produce sufficient heat to heat said polyconductor to its transition temperature, when said liquid level is below said predetermined level, from any initial temperature within the range of -40* F to 330* F.
Claim 8
Dependent Claim
53 words
The device as defined in claim 4 wherein said resistance element, polyconductor and the electrical connection therebetween have a time-temperature lag of between 10 to 60 seconds whereby said resistance element heats said polyconductor to said transition temperature within 10 to 60 seconds of the said liquid level falling below said predetermined level.
Claim 9
Dependent Claim
14 words
The device as defined in claim 6 wherein said time-temperature lag is 30 seconds.
Claim 10
Dependent Claim
22 words
The device as defined in claim 3 wherein said resistance element and polyconductor are electrically connected in parallel to said current source.
Claim 11
Dependent Claim
51 words
The device as defined in claim 3 wherein said polyconductor has the characteristic that its conductivity above said transition temperature increases as its temperature increases, whereby once said polyconductor becomes conductive the heat produced by current flowing therethrough keeps the polyconductor conductive until the polyconductor is disconnected from the current source.
Claim 12
Dependent Claim
109 words
A temperature activated differential medium sensing switch device comprising a current source, an electrical resistance element operatively connected to said source, a first heat sink comprising a first heat conducting medium, a second heat sink comprising a second heat conducting medium, and a polyconductor having a predetermined transition temperature selected at a temperature above the temperature to which said first heat conducting medium is normally subjected, said polyconductor being thermally connected to said resistance element and said rEsistance element having a resistance value selected to heat said polyconductor to a temperature above said transition temperature in a transition of said element from said first medium to said second medium.
Claim 13
Dependent Claim
109 words
A temperature activated differential medium sensing switch device comprising a current source, an electrical resistance element operatively connected to said source, a first heat sink comprising a first heat conducting medium, a second heat sink comprising a second heat conducting medium, and a polyconductor having a predetermined transition temperature selected at a temperature above the temperature to which said first heat conducting medium is normally subjected, said polyconductor being thermally connected to said resistance element and said rEsistance element having a resistance value selected to heat said polyconductor to a temperature above said transition temperature in a transition of said element from said first medium to said second medium.
References Cited (Backward Citations)
US3475745A
Cited
US3543104A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-11-04 | 1978-05-06 | 1978-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-04 | 1982-05-06 | 1982-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-04 | 1986-05-06 | 1986-11-05 | $7700.00 | Window Closed / Lapsed |