US3909813A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ionization-type fire sensor
Assignee: Cerberus AG
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Filing: 1973-06-28
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Granted: 1975-09-30
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Expires: 1993-06-28
Abstract
Abstract An ionization chamber includes an ionizing element which, in combination with an electrical circuit, is so arranged that the electrical resistance of the chamber increases when smoke, or fire aerosols are detected; the sensor further includes an electrical circuit which has a first threshold detector responsive to a first threshold value of increase of resistance to permit generation of a warning signal, and a second threshold level with a second threshold detector, which responds upon exceeding of the second threshold level to provide an alarm signal different from the first warning signal arising at the first threshold level. Preferably, the warning signal is a constantly arising current, and the alarm signal is a signal of varying intensity.
Inventors
- 👤 Andreas Scheidweiler
- 👤 Hanspeter Thalmann
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 20:29
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11; G08B25/00; G08B25/01; G08B25/04
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
177 words
Ionization-type fire sensor comprising an ion chamber (3) accessible to atmosphere subject to fire aerosols, smoke or the like, said ion chamber having electrical resistance which, upon detection of fire aerosols or smoke therein changes in resistance valuE, wherein the improvement comprises two threshold detectors of different threshold levels, a first threshold detector (7) connected to the ion chamber (3) sensitive to a first resistance condition of the chamber and having a first threshold level to provide a first warning output signal when the resistance value of the ion chamber changes and passes a first threshold level; and a second threshold detector (9, 10, 12) connected to the ion chamber sensitive to a second resistance condition, higher than the first condition, and having a second threshold level, higher than the first, to provide a second alarm output signal when the resistance value of the ion chamber passes a second level, higher than said first level; and wherein said second alarm output signal provided by said second threshold detector differs in characteristic from said first warning output signal.
Claim 2
Dependent Claim
177 words
Ionization-type fire sensor comprising an ion chamber (3) accessible to atmosphere subject to fire aerosols, smoke or the like, said ion chamber having electrical resistance which, upon detection of fire aerosols or smoke therein changes in resistance valuE, wherein the improvement comprises two threshold detectors of different threshold levels, a first threshold detector (7) connected to the ion chamber (3) sensitive to a first resistance condition of the chamber and having a first threshold level to provide a first warning output signal when the resistance value of the ion chamber changes and passes a first threshold level; and a second threshold detector (9, 10, 12) connected to the ion chamber sensitive to a second resistance condition, higher than the first condition, and having a second threshold level, higher than the first, to provide a second alarm output signal when the resistance value of the ion chamber passes a second level, higher than said first level; and wherein said second alarm output signal provided by said second threshold detector differs in characteristic from said first warning output signal.
Claim 3
Dependent Claim
25 words
Sensor according to claim 1 wherein the warning output signal is a continuous signal, and the alarm output signal is a signal of changing intensity.
Claim 4
Dependent Claim
31 words
Sensor according to claim 1 wherein the first threshold detector comprises an FET (7), the gate electrode (6) of the FET being controlled by the voltage drop across said ionization chamber.
Claim 5
Dependent Claim
39 words
Sensor according to claim 3 wherein said FET (7) is connected to the ionization chamber to become conductive when said first threshold level is passed; and a light-emitting indicating means (11) connected in the source-drain path of the FET.
Claim 6
Dependent Claim
55 words
Sensor according to claim 3 wherein the second threshold detector comprises a transistor (12), the base of which being controlled by the current through the FET (7), the transistor being connected to become conductive when the voltage drop across the ionization chamber, and thus the current through the FET (7) passes said second threshold level.
Claim 7
Dependent Claim
85 words
Sensor according to claim 5 further comprising a second ionization chamber (4) forming a reference ionization chamber, connected in series with said ionization chamber accessible to atmosphere; the collector-emitter path of said transistor (12) forming a parallel circuit to the series circuit formed by said ionization chambers; a resistor in series with said series connection of said chambers (3, 4) and the parallel connected transistor (12), and voltage supply lines (1, 2) connected to the free terminals of said parallel circuits, and said resistor (5).
Claim 8
Dependent Claim
21 words
Sensor according to claim 6 wherein the resistor (5) is a variable resistor to adjustably set said first warning threshold level.
Claim 9
Dependent Claim
20 words
Sensor according to claim 1 further comprising an alarm indicator (11), said alarm indicator providing a visual alarm indicating output.
Claim 10
Dependent Claim
18 words
Sensor according to claim 8 wherein said alarm indicator is a light emitting diode (LED 11, 16, 17).
Claim 11
Dependent Claim
70 words
Sensor according to claim 1 further comprising a light source (16) controlled to be illuminated when said first threshold level is passed; a photosensitive sensor (21) disposed in light receiving relationship to said light emitting element, and a warning control line (20) connected to said photosensitive sensor, said warning control line having a signal placed thereon when said photosensitive sensor changes resistance due to illumination by said light emitting element.
Claim 12
Dependent Claim
65 words
Sensor according to claim 1 further comprising a current sensor (W); a warning output signal line (20), said current sensor (W) being connected in an electrical circuit to said warning signal line, said warning signal line being activated and having current passing therethrough when said first threshold is passed, and providing a signal to said current, independently of the alarm signal, and in advance thereof.
Claim 13
Dependent Claim
37 words
Sensor according to claim 1 further comprising a signal central, and discrete signalling transmission links between the individual sensors and said signal central, said links being different for the warning output signal and the alarm output signal.
Claim 14
Dependent Claim
30 words
Sensor according to claim 1 comprising means (34, 35, 36) to suppress the warning output signal upon response of the second threshold detector which generates said second alarm output signal.
Claim 15
Dependent Claim
44 words
Sensor according to claim 1 further comprising a self holding or self locking circuit connected to the second threshold detector to hold the second alarm output signal even if said second threshold detector no longer senses conditions in excess of said second threshold level.
Claim 16
Dependent Claim
59 words
Sensor according to claim 1 wherein the first threshold detector comprises a FET (7), the gate electrode of which is controlled by the voltage drop across the ionization chamber; a switching transistor (22) is provided, the base of which is controlled by current through the FET (7), said switching transistor becoming conductive after the first threshold level is passed.
Claim 17
Dependent Claim
29 words
Sensor according to claim 15 further comprising an oscillator controlled by conduction of said transistor (22) to provide a-c signals indicative that said first threshold level has been passed.
Claim 18
Dependent Claim
16 words
Sensor according to claim 16 wherein said oscillator (FIG. 5) comprises a multivibrator-type oscillator (23, 24).
Claim 19
Dependent Claim
58 words
Sensor according to claim 15 further comprising (FIG. 6) a circiut (35) of low a-c impedance connected between the supply lines (1, 2) to the sensor; and a controlled switch (34) connected to and controlled by said transistor (22) and switching said low a-c impedance circuit (35) in parallel to the sensor upon conduction of said transistor (22).
Claim 20
Dependent Claim
75 words
Sensor according to claim 15 comprising an additional transistor (12), the base of which is controlled by the current through the FET (7), and voltage divider means in the source-drain path of the FET (7) setting the threshold response levels of said switching transistor (22) and said additional transistor (12) to be at different levels to provide said first and second threshold levels, conduction of said transistors, respectively, controlling said first and second output signals.
Claim 21
Dependent Claim
67 words
Sensor according to claim 1 further comprising (FIG. 6) a circuit (35) of low a-c impedance connected between the supply lines (1, 2) to the sensor; and a controlled switch (34) connected to and controlled by said first threshold detector (7) and switching said a-c low impedance circuit (35) in parallel to the sensor when the first threshold level of the first threshold detector (7) is exceeded.
References Cited (Backward Citations)
US3665441A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-09-29 | 1979-03-31 | 1979-09-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-09-29 | 1983-03-31 | 1983-09-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-09-29 | 1987-03-31 | 1987-09-30 | $7700.00 | Window Closed / Lapsed |