US4027165A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Ionization detection system for aerosols
Assignee: Energy Research and Development Administration ERDA
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Filing: 1976-02-17
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Granted: 1977-05-31
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Expires: 1996-02-17
Abstract
Abstract This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber.
Inventors
- 👤 Martin E. Jacobs
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 16:26
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11; G08B17/113
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
120 words
In a system for detecting colloidally suspended particles in a gas, said system including a measuring ionization chamber which is open to said gas, said chamber having a pair of spaced electrodes for establishing an electric field therebetween, a source of radiation for ionizing molecules of said gas in said region, and a first radiation shield positioned in partial overlap with said source for preventing part of said radiation from penetrating said region, the improvement comprising: a second radiation shield mounted between said first shield and said region, and means responsive to changes in ambient temperature for supporting the second shield and moving the same relative to the first shield to offset temperature-induced variations in the sensitivity of said chamber.
Claim 2
Dependent Claim
120 words
In a system for detecting colloidally suspended particles in a gas, said system including a measuring ionization chamber which is open to said gas, said chamber having a pair of spaced electrodes for establishing an electric field therebetween, a source of radiation for ionizing molecules of said gas in said region, and a first radiation shield positioned in partial overlap with said source for preventing part of said radiation from penetrating said region, the improvement comprising: a second radiation shield mounted between said first shield and said region, and means responsive to changes in ambient temperature for supporting the second shield and moving the same relative to the first shield to offset temperature-induced variations in the sensitivity of said chamber.
Claim 3
Dependent Claim
19 words
The system of claim 1 wherein said source and the first and second shield are of generally circular configuration.
Claim 4
Dependent Claim
16 words
The system of claim 2 wherein said source and the first and second shield are coaxial.
Claim 5
Dependent Claim
12 words
The system of claim 1 wherein said means comprises a bimetallic strip.
Claim 6
Dependent Claim
29 words
The system of claim 4 wherein one end of said strip is affixed to the second shield, and the other end of said strip is affixed to said chamber.
Claim 7
Dependent Claim
142 words
In a system for detecting colloidally suspended particles in a gas, said system including a measuring ionization chamber which is open to said gas, said chamber having a pair of spaced electrodes for establishing an electric field in the region therebetween, an annular radiation source coaxially disposed within said chamber for ionizing molecules of said gas in said region to establish ionic current flow through an electric circuit connected across said electrodes, and alarm means actuated by a decrease in said ionic current flow, the improvement comprising: an annular radiation shield extending about and in partial overlap with said source, and a bimetallic arm having an end connected to said shield for moving the same to vary the extent of said overlap inversely with changes in ambient temperature and thus stabilize said ionic current flow with respect to changes in said temperature.
Claim 8
Dependent Claim
142 words
In a system for detecting colloidally suspended particles in a gas, said system including a measuring ionization chamber which is open to said gas, said chamber having a pair of spaced electrodes for establishing an electric field in the region therebetween, an annular radiation source coaxially disposed within said chamber for ionizing molecules of said gas in said region to establish ionic current flow through an electric circuit connected across said electrodes, and alarm means actuated by a decrease in said ionic current flow, the improvement comprising: an annular radiation shield extending about and in partial overlap with said source, and a bimetallic arm having an end connected to said shield for moving the same to vary the extent of said overlap inversely with changes in ambient temperature and thus stabilize said ionic current flow with respect to changes in said temperature.
Claim 9
Dependent Claim
17 words
The system of claim 6 wherein the other end of said arm in connected to said chamber.
Claim 10
Dependent Claim
24 words
The system of claim 7 wherein said other end of said arm is connected to said chamber by a member whose length is adjustable.
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) | 1980-05-30 | 1980-11-29 | 1981-05-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-05-30 | 1984-11-29 | 1985-05-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-05-30 | 1988-11-29 | 1989-05-31 | $7700.00 | Window Closed / Lapsed |