US3576472A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Device for sensing flowable material
Assignee: Aladdin Industries LLC
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Filing: 1968-04-18
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Granted: 1971-04-27
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Expires: 1988-04-18
Abstract
Abstract A device for sensing the presence or absence of a flowable material in response to the thermal conductivity thereof, comprising a probe including first and second thermistors adapted to be surrounded by flowable material, energizing means for energizing said first thermistor with sufficient power to cause substantial heating thereof, said energizing means including means for supplying said second thermistor with a small amount of power insufficient to cause substantial heating thereof, said second thermistor affording a reference resistance responsive to the ambient temperature of the flowable material, a cycle timer connected to said energizing means for alternately energizing and deenergizing said first thermistor, said first thermistor being energized for a heating cycle and then deenergized for a cooling cycle, a comparator comprising a differential amplifier for comparing the voltages across said first and second thermistors, a trigger device connected to said differential amplifier and having first and second outputs which are activated alternately in accordance with whether the resistance of said first thermistor is above or below a predetermined control point, first and second gates connected to said first and second outputs, a delay timer connected to said cycle timer and including a pulse generator for generating a momentary pulse after a predetermined delay from the beginning of said heating cycle, means for supplying said momentary pulse to said gates to actuate said gates, a memory device having first and second inputs connected to said gates, said memory device being operable alternately to first and second states in response to pulses from said gates, and means including an output relay connected to said memory device to indicate the state of said memory device.
Inventors
- 👤 John F Marshall
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 12:27
CPC Classifications
G; G01; G01P; G01P13/00; G01P13/0006; G01P13/006; G01F; G01F1/00; G01F1/68; G01F1/696
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
129 words
A device for sensing the presence or absence of a material by utilizing the thermal conductivity of the material, comprising the combination of: a probe including a thermistor adapted to be surrounded by a material, energizing means for selectively supplying sufficient electrical power to said thermistor so as to cause the resistance of said thermistor to be responsive to the heating of said thermistor by said energizing mEans and the thermal conductivity of the material surrounding the probe, a cycle timer for causing said energizing means to energize said thermistor for a heating cycle and then causing said thermistor to be deenergized for a cooling cycle, and additional means for detecting a change in the resistance of said thermistor at a predetermined time during the cycle of said timer.
Claim 2
Independent Claim
129 words
A device for sensing the presence or absence of a material by utilizing the thermal conductivity of the material, comprising the combination of: a probe including a thermistor adapted to be surrounded by a material, energizing means for selectively supplying sufficient electrical power to said thermistor so as to cause the resistance of said thermistor to be responsive to the heating of said thermistor by said energizing mEans and the thermal conductivity of the material surrounding the probe, a cycle timer for causing said energizing means to energize said thermistor for a heating cycle and then causing said thermistor to be deenergized for a cooling cycle, and additional means for detecting a change in the resistance of said thermistor at a predetermined time during the cycle of said timer.
Claim 3
Dependent Claim
53 words
A device according to claim 1, in which said energizing means comprises a power supply, and an electronic switch connected between said power supply and said thermistor, said cycle timer comprising an electronic timing device for causing said electronic switch to be conductive during said heating cycle and nonconductive during said cooling cycle.
Claim 4
Dependent Claim
34 words
A combination according to claim 2, in which said additional means includes a delay device connected to said electronic timing device for actuating said measuring means during said heating cycle after a predetermined delay.
Claim 5
Dependent Claim
41 words
A device according to claim 1, in which said additional means comprises a delay timing device operable by said cycle timer during said heating cycle for actuating said additional means after a predetermined delay from the beginning of said heating cycle.
Claim 6
Independent Claim
123 words
A device for sensing the presence or absence of a flowable material by sensing the thermal conductivity of the flowable material, comprising the combination of: a probe including first and second thermistors adapted to be surrounded by flowable material, energizing means for energizing said first thermistor with sufficient power to cause the resistance of said thermistor to be responsive to the heating thereof whereby the temperature and resistance of said first thermistor will vary in accordance with the thermal conductivity of the flowable material around said probe, and additional means for comparing the resistance of said first thermistor with the resistance of said second thermistor, said second thermistor providing a reference resistance which is responsive to the ambient temperature of said flowable material.
Claim 7
Independent Claim
123 words
A device for sensing the presence or absence of a flowable material by sensing the thermal conductivity of the flowable material, comprising the combination of: a probe including first and second thermistors adapted to be surrounded by flowable material, energizing means for energizing said first thermistor with sufficient power to cause the resistance of said thermistor to be responsive to the heating thereof whereby the temperature and resistance of said first thermistor will vary in accordance with the thermal conductivity of the flowable material around said probe, and additional means for comparing the resistance of said first thermistor with the resistance of said second thermistor, said second thermistor providing a reference resistance which is responsive to the ambient temperature of said flowable material.
Claim 8
Dependent Claim
53 words
A device according to claim 5, in which said additional means comprises additional energizing means for supplying said second thermistor with a small amount of electrical power which is insufficient to cause substantial heating of said second thermistor, and an electronic comparison device for comparing the voltages across said first and second thermistors.
Claim 9
Dependent Claim
17 words
A device according to claim 6, in which said electronic comparison device comprises an electronic differential amplifier.
Claim 10
Dependent Claim
68 words
A device according to claim 5, including a cycle timer connected to said energizing means for alternately energizing and deenergizing said first thermistor, said first thermistor being energized for a heating cycle and deenergized for a cooling cycle, and means connecting said additional means to said cycle timer whereby said additional means is effective to compare the resistance of said first and second thermistors during said heating cycle.
Claim 11
Dependent Claim
41 words
A device according to claim 8, in which said additional means includes a delay timer operable by said cycle timer for momentarily actuating said additional means to compare said resistances after a predetermined delay from the beginning of said heating cycle.
Claim 12
Dependent Claim
54 words
A device according to claim 9, in which said delay timer comprises a pulse generator to produce a momentary pulse for causing said additional means to compare said resistances, and a delay device connected to said cycle timer for triggering said pulse generator after a predetermined delay from the beginning of said heating cycle.
Claim 13
Dependent Claim
42 words
A device according to claim 10, including additional energizing means for energizing said second thermistor with a small amount of power insufficient to cause substantial heating hereof, said additional means including means for comparing the voltages across said first and second thermistors.
Claim 14
Dependent Claim
70 words
A device according to claim 11, in which said last mentioned means comprises an electronic trigger device having two outputs which are actuated alternately when the voltage across said first thermistor is above or below a predetermined control point relative to the voltage across said second thermistor, first and second gates connected to said outputs, and means for supplying said momentary pulse to said gates for momentarily actuating said gates.
Claim 15
Dependent Claim
44 words
A device according to claim 12, including an electronic memory device connected to the outputs of said first and second gates, said memory device having first and second states which are assumed and maintained in response to signals from said first and second gates.
Claim 16
Dependent Claim
33 words
A device according to claim 13, including an output device connected to said memory device and operable to two different conditions in response to the first and second states of said memory device.
Claim 17
Dependent Claim
30 words
A device according to claim 14, in which said output device comprises a relay which is energized in one state and deenergized in the other state of said memory device.
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) | 1974-04-26 | 1974-10-26 | 1975-04-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-04-26 | 1978-10-26 | 1979-04-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-04-26 | 1982-10-26 | 1983-04-27 | $7700.00 | Window Closed / Lapsed |