US3714641A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ionization fire alarm
Assignee: Cerberus AG
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Filing: 1970-03-13
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Granted: 1973-01-30
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Expires: 1990-03-13
Abstract
Abstract An ionization fire alarm utilizing at least one transistor with high input resistance, such transistor being a field-effect transistor of the enhancement type having a threshold voltage above 7 volts. Further, the voltage value of the voltage source and the resistance value of a resistor element are selected such that the voltage drop at the ionization chamber without the influence of combustion aerosols is smaller than the threshold voltage of the field-effect transistor so that the field-effect transistor is therefore non-conductive or blocked, and additionally these values are simultaneously chosen such that the field strength, in the chamber regions of the ionization chamber in which at least 85 percent of the ionization current flows, is smaller than 5 V/cm.
Inventors
- 👤 A Scheidweiler
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 19:10
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
267 words
An ionization fire alarm comprising an ionization chamber accessible to the surrounding air, said ionization chamber being provided with two electrodes, a source of direct-current voltage, a resistance element with two terminals, one electrode of said ionization chamber being connected to one terminal of said resistance element and the other electrode of said ionization chamber and the other terminal of said resistance element being connected to said direct-current voltage source, an electric circuit incorporating at least one field-effect transistor having gate, source, and drain electrodes, the gate electrode of said field-effect transistor being connected to the connection point of said one electrode of said ionization chamber and said one terminal of said resistance element, the source and drain electrodes being electrically connected to said voltage source, said field-effect transistor being of the enhancement type and having a threshold voltage above 7 volts, the control path of said transistor connected directly parallel to the measuring ionization chamber without the need for further auxiliary elements, said direct-current voltage source having a voltage value and said resistance element having a resistance value such that the voltage drop across said two electrodes of said ionization chamber without the influence of combustion aerosols is smaller than said threshold voltage of said field-effect transistor, whereby said field-effect transistor is nonconductive, and said voltage source having a voltage value and said two electrodes of said ionization chamber being spaced from one another by an amount such that the field strength in the chamber regions of the ionization chamber in which at least 85 percent of the ionization current flows, is smaller than 5 V/cm.
Claim 2
Dependent Claim
267 words
An ionization fire alarm comprising an ionization chamber accessible to the surrounding air, said ionization chamber being provided with two electrodes, a source of direct-current voltage, a resistance element with two terminals, one electrode of said ionization chamber being connected to one terminal of said resistance element and the other electrode of said ionization chamber and the other terminal of said resistance element being connected to said direct-current voltage source, an electric circuit incorporating at least one field-effect transistor having gate, source, and drain electrodes, the gate electrode of said field-effect transistor being connected to the connection point of said one electrode of said ionization chamber and said one terminal of said resistance element, the source and drain electrodes being electrically connected to said voltage source, said field-effect transistor being of the enhancement type and having a threshold voltage above 7 volts, the control path of said transistor connected directly parallel to the measuring ionization chamber without the need for further auxiliary elements, said direct-current voltage source having a voltage value and said resistance element having a resistance value such that the voltage drop across said two electrodes of said ionization chamber without the influence of combustion aerosols is smaller than said threshold voltage of said field-effect transistor, whereby said field-effect transistor is nonconductive, and said voltage source having a voltage value and said two electrodes of said ionization chamber being spaced from one another by an amount such that the field strength in the chamber regions of the ionization chamber in which at least 85 percent of the ionization current flows, is smaller than 5 V/cm.
Claim 3
Dependent Claim
267 words
An ionization fire alarm comprising an ionization chamber accessible to the surrounding air, said ionization chamber being provided with two electrodes, a source of direct-current voltage, a resistance element with two terminals, one electrode of said ionization chamber being connected to one terminal of said resistance element and the other electrode of said ionization chamber and the other terminal of said resistance element being connected to said direct-current voltage source, an electric circuit incorporating at least one field-effect transistor having gate, source, and drain electrodes, the gate electrode of said field-effect transistor being connected to the connection point of said one electrode of said ionization chamber and said one terminal of said resistance element, the source and drain electrodes being electrically connected to said voltage source, said field-effect transistor being of the enhancement type and having a threshold voltage above 7 volts, the control path of said transistor connected directly parallel to the measuring ionization chamber without the need for further auxiliary elements, said direct-current voltage source having a voltage value and said resistance element having a resistance value such that the voltage drop across said two electrodes of said ionization chamber without the influence of combustion aerosols is smaller than said threshold voltage of said field-effect transistor, whereby said field-effect transistor is nonconductive, and said voltage source having a voltage value and said two electrodes of said ionization chamber being spaced from one another by an amount such that the field strength in the chamber regions of the ionization chamber in which at least 85 percent of the ionization current flows, is smaller than 5 V/cm.
Claim 4
Dependent Claim
267 words
An ionization fire alarm comprising an ionization chamber accessible to the surrounding air, said ionization chamber being provided with two electrodes, a source of direct-current voltage, a resistance element with two terminals, one electrode of said ionization chamber being connected to one terminal of said resistance element and the other electrode of said ionization chamber and the other terminal of said resistance element being connected to said direct-current voltage source, an electric circuit incorporating at least one field-effect transistor having gate, source, and drain electrodes, the gate electrode of said field-effect transistor being connected to the connection point of said one electrode of said ionization chamber and said one terminal of said resistance element, the source and drain electrodes being electrically connected to said voltage source, said field-effect transistor being of the enhancement type and having a threshold voltage above 7 volts, the control path of said transistor connected directly parallel to the measuring ionization chamber without the need for further auxiliary elements, said direct-current voltage source having a voltage value and said resistance element having a resistance value such that the voltage drop across said two electrodes of said ionization chamber without the influence of combustion aerosols is smaller than said threshold voltage of said field-effect transistor, whereby said field-effect transistor is nonconductive, and said voltage source having a voltage value and said two electrodes of said ionization chamber being spaced from one another by an amount such that the field strength in the chamber regions of the ionization chamber in which at least 85 percent of the ionization current flows, is smaller than 5 V/cm.
Claim 5
Dependent Claim
18 words
An ionization fire alarm as defined in claim 1, wherein said resistance element is a second ionization chamber.
Claim 6
Dependent Claim
19 words
An ionization fire alarm as defined in claim 2, wherein said second ionization chamber has a saturated ion current.
Claim 7
Dependent Claim
36 words
An ionization fire alarm as defined in claim 1, wherein said at least one ionization chamber is connected in parallel between the gate electrode and one of said source or drain electrodes of the field-effect transistor.
Claim 8
Dependent Claim
29 words
An ionization fire alarm as defined in claim 1, wherein the source electrode of the field effect transistor is electrically connected with the control electrode of a further transistor.
Claim 9
Dependent Claim
25 words
An ionization fire alarm as defined in claim 5, wherein said field-effect transistor and at least said further transistor are connected in an integrated circuit.
Claim 10
Dependent Claim
20 words
An ionization fire alarm as defined in claim 6, further including a load resistor constituting part of said integrated circuit.
Claim 11
Dependent Claim
29 words
An ionization fire alarm as defined in claim 1, wherein the drain electrode of the field effect transistor is electrically connected with the control electrode of a further transistor.
Claim 12
Dependent Claim
25 words
An ionization fire alarm as defined in claim 8, wherein said field-effect transistor and at least said further transistor are connected in an integrated circuit.
Claim 13
Dependent Claim
20 words
An ionization fire alarm as defined in claim 9, further including a load resistor constituting part of said integrated circuit.
Claim 14
Dependent Claim
17 words
An ionization fire alarm as defined in claim 1, wherein said electric circuit includes a current-limiting resistance.
Claim 15
Dependent Claim
40 words
An ionization fire alarm as defined in claim 1, wherein said electric circuit is provided with a current flow path composed exclusively of controlled semiconductors through which current flow path the main current flows in the event of an alarm.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-01-30 | 1976-07-31 | 1977-01-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-01-30 | 1980-07-31 | 1981-01-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-01-30 | 1984-07-31 | 1985-01-30 | $7700.00 | Window Closed / Lapsed |