Patent US3967238A successfully refreshed from Google Patents.
US3967238A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Low-brake fluid sensor
Assignee: Northrop Grumman Space and Mission Systems Corp
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Filing: 1974-12-16
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Granted: 1976-06-29
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Expires: 1994-12-16
Abstract
Abstract A liquid level sensor for sensing the levels of brake fluid in the master cylinders of a vehicle having probes for insertion into the fluids of the master cylinders and threshold detector circuits, associated with the probes and having an integrator coupled to the probes for providing a signal to activate a warning mechanism such as a lamp when the level of the liquid in either cylinder falls below a predetermined level. A protection circuit is coupled to the threshold detector circuits for protecting them against excessive transient voltages or a reverse supply potential. An additional circuit is coupled to a monitoring system which monitors the differential pressure switch which is activated in response to a difference in pressure in the two master cylinders. A self-check circuit is also coupled to the threshold detectors to activate the warning lamp in response to a signal from the ignition switch. The threshold detectors are failsafe in that a failed detector will activate the alarm indicating a failure rather than permit it to go undetected.
Inventors
- 👤 Robert R. Ridpath
- 👤 Louis R. Clifford
- 👤 Hendrik Groot
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 11:17
CPC Classifications
B; B60; B60T; B60T17/00; B60T17/18; B60T17/22; B60T17/225; G; G01; G01F; G01F23/00; G01F23/22; G01F23/24; G01F23/241
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
167 words
A fluid sensor system for sensing the level of fluid in a container comprising: electrical supply means for supplying an electrical potential, electrical probe means coupled to said electrical supply means and inserted into the fluid for providing an electrical signal in proportion to the level of fluid in the container, detector circuit means coupled to said probe means for detecting said electrical signals, said detector circuit means including an integrator circuit coupled to said probe means for integrating said electrical signal with respect to time, said detector circuit further including an amplifier having an input coupled to the output of said integrating circuit for amplifying said integrated electrical signal, and switching means operatively coupled to said detector circuit means and responsive to said amplifier, said switching means being operable to be switched from one stable state to a second stable state in response to a predetermined signal from said detector circuit to provide an accurate alarm signal in response to a reduced level of said fluid.
Claim 2
Dependent Claim
167 words
A fluid sensor system for sensing the level of fluid in a container comprising: electrical supply means for supplying an electrical potential, electrical probe means coupled to said electrical supply means and inserted into the fluid for providing an electrical signal in proportion to the level of fluid in the container, detector circuit means coupled to said probe means for detecting said electrical signals, said detector circuit means including an integrator circuit coupled to said probe means for integrating said electrical signal with respect to time, said detector circuit further including an amplifier having an input coupled to the output of said integrating circuit for amplifying said integrated electrical signal, and switching means operatively coupled to said detector circuit means and responsive to said amplifier, said switching means being operable to be switched from one stable state to a second stable state in response to a predetermined signal from said detector circuit to provide an accurate alarm signal in response to a reduced level of said fluid.
Claim 3
Dependent Claim
42 words
The fluid sensor system of claim 1 and wherein said amplifier is an inverting amplifier and said detector circuit further includes a NOR gate having an input coupled to the output of said amplifier and an output coupled to said switching means.
Claim 4
Dependent Claim
21 words
The sensor as described in claim 2 and wherein said inverting amplifier and said NOR gate are formd of CMOS circuitry.
Claim 5
Dependent Claim
40 words
The fluid sensor system of claim 1 and wherein said switching means includes a transistor having an input coupled to said detector and responsive to said amplifier to be switched from said one stable state to said second stable state.
Claim 6
Dependent Claim
36 words
The sensor as described in claim 1, and wherein said electrical supply means includes current limiting circuit means for providing a relatively low current to said electrical probe means to thereby prevent ionization of the fluid.
Claim 7
Dependent Claim
30 words
The sensor as described in claim 1 and wherein said container is conductive and grounded and said electrical probe means is effectively series connected through the fluid to the container.
Claim 8
Dependent Claim
176 words
A fluid sensor system for sensing the level of fluid in a container comprising: electrical supply means for supplying an electrical potential, electrical probe means coupled to said electrical supply means and inserted into the fluid for providing an electrical signal in proportion to the level of fluid in the container, detector circuit means coupled to said probe means for detecting said electrical signals, said detector circuit means including an integrator circuit coupled to said probe means for integrating said electrical signal with respect to time, switching means operatively coupled to said detector circuit means for switching its state in response to a predetermined signal from said detector circuit to provide an accurate alarm signal in response to a reduced level of said fluid, and protection means coupled to said electrical supply means for providing protection of said sensor from transient and reverse voltages, said protection means including a resistor-capacitor network coupled to said electrical supply means for providing protection from transient voltage and a diode coupled to said electrical supply means for shunting reverse voltages.
Claim 9
Dependent Claim
176 words
A fluid sensor system for sensing the level of fluid in a container comprising: electrical supply means for supplying an electrical potential, electrical probe means coupled to said electrical supply means and inserted into the fluid for providing an electrical signal in proportion to the level of fluid in the container, detector circuit means coupled to said probe means for detecting said electrical signals, said detector circuit means including an integrator circuit coupled to said probe means for integrating said electrical signal with respect to time, switching means operatively coupled to said detector circuit means for switching its state in response to a predetermined signal from said detector circuit to provide an accurate alarm signal in response to a reduced level of said fluid, and protection means coupled to said electrical supply means for providing protection of said sensor from transient and reverse voltages, said protection means including a resistor-capacitor network coupled to said electrical supply means for providing protection from transient voltage and a diode coupled to said electrical supply means for shunting reverse voltages.
Claim 10
Independent Claim
208 words
A system for sensing the level of fluids on the master cylinder reservoirs of a vehicle comprising: electrical supply means for supplying an electrical potential a plurality of probe means each coupled to said electrical supply means and each inserted into one of the cylinder reservoirs and each adapted to generate an electrical signal indicating the safe level presence of fluid in the associated cylinder reservoir, a plurality of detector circuits each coupled to one of said probe means for detecting the electrical signal generated by the associated probe means, each of said detector circuits including an integrator circuit for integrating the associated electrical signal with respect to time, with each of said detector circuits further including an amplifier coupled to the output of the associated integrator circuit, switching means coupled to the output of each detector circuit, said switching means being operable to switch from one stable state to a second stable state in response to a predetermined signal from any of said detector circuits to provide an alarm signal in response to a reduced level of liquid in either of said cylinders, and self-check circuitry coupled to each of said amplifiers to provide an alarm signal in response to a malfunction in any of said amplifiers.
Claim 11
Independent Claim
208 words
A system for sensing the level of fluids on the master cylinder reservoirs of a vehicle comprising: electrical supply means for supplying an electrical potential a plurality of probe means each coupled to said electrical supply means and each inserted into one of the cylinder reservoirs and each adapted to generate an electrical signal indicating the safe level presence of fluid in the associated cylinder reservoir, a plurality of detector circuits each coupled to one of said probe means for detecting the electrical signal generated by the associated probe means, each of said detector circuits including an integrator circuit for integrating the associated electrical signal with respect to time, with each of said detector circuits further including an amplifier coupled to the output of the associated integrator circuit, switching means coupled to the output of each detector circuit, said switching means being operable to switch from one stable state to a second stable state in response to a predetermined signal from any of said detector circuits to provide an alarm signal in response to a reduced level of liquid in either of said cylinders, and self-check circuitry coupled to each of said amplifiers to provide an alarm signal in response to a malfunction in any of said amplifiers.
Claim 12
Dependent Claim
148 words
The system as described in claim 8 and wherein said self-check circuitry includes electrical circuit means coupled to said electrical supply means and each of said amplifiers for providing a normally high voltage logic 1 signal, an inverting amplifier having an input coupled to said electrical circuit means, and a diode coupled between the output of said inverting amplifier and each of said plurality of detector circuits for isolating the output of said inverting amplifier from the remainder of the system when the system is operating in the normal mode whereby a malfunction in any of said amplifiers is operative to change the logic state of said electrical circuit means from a logic 1 state to a logic 0 state to thereby activate said inverting amplifier to transmit a signal from said inverting amplifier to said detector circuits to signal a malfunction in one of said inverting amplifiers.
Claim 13
Dependent Claim
72 words
The system as described in claim 8 and wherein each of said amplifiers of said detector circuits is an inverting amplifier and further including a NOR gate with the output of each of said inverting amplifiers coupled to the input of said NOR gate, said NOR gate having an output coupled to said switching means with each of said inverting amplifiers and said NOR gate constructed to provide probe to logic interfacing.
Claim 14
Dependent Claim
62 words
The sensor as described in claim 7, and wherein said electrical supply means includes a voltage divider circuit and a current limiting circuit operatively coupled to said voltage divider circuit for providing a relatively small current whereby the parameters of said voltage divider circuit and said current limiting circuit are adjusted to prevent false alarm signals over a wide range of temperatures.
Claim 15
Dependent Claim
36 words
The sensor as described in claim 7 and wherein said container is nonconductive and said electrical probe means includes two probes each fixedly mounted on a nonconductive supporting member and effectively series connected through the fluid.
Claim 16
Dependent Claim
21 words
The system as described in claim 10 and wherein said inverting amplifiers and said NOR gate are formed of CMOS design.
Claim 17
Dependent Claim
39 words
The system as described in claim 8 and wherein said self-check circuitry is coupled to a monitoring system which includes at least one differential pressure switch for monitoring the pressure in at least one master cylinder of the vehicle.
Claim 18
Dependent Claim
48 words
The system as described in claim 9 and wherein said electrical supply means includes a current limiting circuit for providing a relatively low current to said plurality of said probe means to thereby prevent ionization of said fluid, and said diode is coupled to said current limiting circuit.
Claim 19
Dependent Claim
76 words
The system as described in claim 10 and wherein said electrical supply means includes: a voltage divider circuit, a current limiting circuit operatively coupled to said voltage divider circuit for providing a relatively small current whereby the parameters of said voltage divider circuit and said current limiting circuit are adjusted to prevent false alarm signals over a wide range of temperatures, and said diode is coupled to said voltage divider circuit and said current limiting circuit.
References Cited (Backward Citations)
US3312936A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-06-29 | 1979-12-29 | 1980-06-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-06-29 | 1983-12-29 | 1984-06-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-06-29 | 1987-12-29 | 1988-06-29 | $7700.00 | Window Closed / Lapsed |