US3676678A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Single chamber ionization smoke detector
Assignee: Nittan Co Ltd
•
Filing: 1970-02-10
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Granted: 1972-07-11
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Expires: 1990-02-10
Abstract
Abstract An ionization smoke detecotor having a single open ionization chamber which is connected with a field effect transistor and wherein the leakage impedance between the gate and drain of the transistor serves as a high impedance path.
Inventors
- 👤 Naoki Takahashi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 17:16
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11; G01; G01N; G01N27/00; G01N27/62; G01N27/64; G01N27/66
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
92 words
An ionization smoke detector comprising a field effect transistor having the source-drain path connected between reference potential points of a power supply and a single opentype ionization chamber including a radioactive source therein connected between the gate electrode of said field effect transistor and one of said reference potential points, said ionization chamber and the gate-drain leakage path forming a voltage divider, whereby the leakage impedance existing between the gate and drain of said field effect traNsistor forms a substantially constant current high resistance path within a selected range of gate voltages.
Claim 2
Dependent Claim
92 words
An ionization smoke detector comprising a field effect transistor having the source-drain path connected between reference potential points of a power supply and a single opentype ionization chamber including a radioactive source therein connected between the gate electrode of said field effect transistor and one of said reference potential points, said ionization chamber and the gate-drain leakage path forming a voltage divider, whereby the leakage impedance existing between the gate and drain of said field effect traNsistor forms a substantially constant current high resistance path within a selected range of gate voltages.
Claim 3
Dependent Claim
33 words
An ionization smoke detector according to claim 1, characterized in that one terminal of the open-type ionization chamber is connected to a variable voltage source to control the sensitivity and facilitate testing operations.
Claim 4
Dependent Claim
18 words
An ionization smoke detector according to claim 1 wherein said field effect transistor is of the junction type.
References Cited (Backward Citations)
US3295121A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-11 | 1976-01-10 | 1976-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-11 | 1980-01-10 | 1980-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-11 | 1984-01-10 | 1984-07-11 | $7700.00 | Window Closed / Lapsed |