US3795904A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Fire alarm with ionization chamber
Assignee: Preussag AG Feuerschutz
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Filing: 1971-05-13
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Granted: 1974-03-05
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Expires: 1991-05-13
Abstract
Abstract In the alarm, a circuit generates a quiescent ionization current between two electrodes in a chamber having a radioactive source. The chamber admits ambient air. Combustion gases from smokeless fires cause additional ionization current. The circuit establishes the quiescent ionization current at a value close to the additional ionization current. Amplifying means in the circuit respond to increases and decreases in the ionization current so as to indicate existance of various types of fires. An alarm device responds to the amplifier. The quiescent current may be within the order of magnitude of the additonal ionization current. Preferably the amplifying means responds to increases and decreases in ionizaton current with an equal quiescent ionization current in a reference chamber.
Inventors
- 👤 H Beyersdorf
- 👤 L Rims
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 12:40
CPC Classifications
G; G08; G08B; G08B17/00; G08B17/10; G08B17/11
Claims Analysis
Total Claims: 26
Claim 1
Independent Claim
149 words
A fire detecting apparatus, comprising structural means forming a chamber and including a pair of electrode means, said chamber having gas access openings, and ionization current generating means for generating a quiescent ionization current between said electrode means in the absence of heat emitted gases so that gases from smokeless fires passing through the access openings produce an added ionization current, said generating means including circuit means connected to said electrode means for producing a signal indicative of the state of the ionization current and radioactive source means located in the chamber and having a radioactivity sufficient to limit the quiescent ionization to the order of magnitude of the added ionization current, said radioactive source means including a substance having a radioactivity up to 0.1 microcuries, said circuit means including amplifying means for amplifying decreases as well as increases in the potential difference between said pair of electrode means.
Claim 2
Dependent Claim
149 words
A fire detecting apparatus, comprising structural means forming a chamber and including a pair of electrode means, said chamber having gas access openings, and ionization current generating means for generating a quiescent ionization current between said electrode means in the absence of heat emitted gases so that gases from smokeless fires passing through the access openings produce an added ionization current, said generating means including circuit means connected to said electrode means for producing a signal indicative of the state of the ionization current and radioactive source means located in the chamber and having a radioactivity sufficient to limit the quiescent ionization to the order of magnitude of the added ionization current, said radioactive source means including a substance having a radioactivity up to 0.1 microcuries, said circuit means including amplifying means for amplifying decreases as well as increases in the potential difference between said pair of electrode means.
Claim 3
Dependent Claim
22 words
An apparatus as in claim 1, wherein said radioactive source means includes a substance having a radioactivity of less than 0.05 microcuries.
Claim 4
Dependent Claim
25 words
An apparatus as in claim 1, wherein one of said electrode means partially surrounds the other so as to form inner and outer electrode means.
Claim 5
Dependent Claim
27 words
An apparatus as in claim 3, wherein said circuit means, when energized, renders the potential of said inner electrode means more negative than said outer electrode means.
Claim 6
Dependent Claim
26 words
An apparatus as in claim 4, wherein said circuit means includes amplifying means having an input connected to said more negative one of said electrode means.
Claim 7
Dependent Claim
31 words
An apparatus as in claim 1, wherein said circuit means includes amplifier means connected across said electrode means and including a field-effect transistor for amplifying potential differences between said electrode means.
Claim 8
Dependent Claim
73 words
An apparatus as in claim 1, wherein said circuit means includes second structural Means forming a reference ionization chamber and second a pair of electrode means, second radioactive source means in said reference ionization chamber, said circuit means connecting said pairs of electrode means in series and forming with said second source means ionization current generating means for producing a reference quiescent ionization current, said reference chamber means being protected from ambient air.
Claim 9
Dependent Claim
37 words
An apparatus as in claim 4, wherein said sources means is arranged in said chamber so that its radiation is in the direction of the potential which is negative with respect to the ions generated by it.
Claim 10
Dependent Claim
21 words
An apparatus as in claim 4, wherein said source means is mounted on the less negative one of said electrode means.
Claim 11
Dependent Claim
40 words
An apparatus as in claim 1, wherein said circuit means includes first amplifying means for responding to decreases in potentials between said electrode means and second amplifying means for responding to increases in the potential difference between said electrode means.
Claim 12
Dependent Claim
15 words
An apparatus as in claim 10, wherein each of said amplifying means includes field-effect transistors.
Claim 13
Dependent Claim
18 words
An apparatus as in claim 11, wherein each of said amplifying means includes two cascade connected field-effect transistors.
Claim 14
Dependent Claim
43 words
An apparatus as in claim 7, wherein said circuit means includes a bridge with each of said pair of electrode means forming an arm of said bridge adjacent the other, and wherein amplifying means in said circuit means indicates unbalance in said bridge.
Claim 15
Dependent Claim
70 words
An apparatus as in claim 1, wherein said circuit means includes time responsive means for responding to the change in ionization currents with respect to time, and threshold means responsive to said time responsive means for producing a first output in response to a change in ionization current less than a predetermined rate and a second output in response to a change in predetermined value greater than a predetermined rate.
Claim 16
Dependent Claim
42 words
An apparatus as in claim 1, wherein said circuit means includes limit means responsive to the ionization current for producing one indication when the ionization current is below a predetermined value and a second indication when the ionization exceeds the predetermined value.
Claim 17
Dependent Claim
37 words
An apparatus as in claim 1, wherein said circuit means includes dust sensing means in the chamber, and control means responsive to said sensing means for varying the ionization current in response to said dust sensing means.
Claim 18
Dependent Claim
15 words
An apparatus as in claim 14, wherein said time responsive means includes a differentiating network.
Claim 19
Dependent Claim
70 words
An apparatus as in claim 15, wherein said circuit means includes time responsive means for responding to the change in ionization currents with respect to time, and threshold means responsive to said time responsive means for producing a first output in response to a change in ionization current less than a predetermined rate and a second output in response to a change in predetermined value greater than a predetermined rate.
Claim 20
Dependent Claim
36 words
An apparatus as in claim 18, said circuit means includes dust sensing means in the chamber, and control means responsive to said sensing means for varying the ionization current in response to said dust sensing means.
Claim 21
Dependent Claim
42 words
An apparatus as in claim 16, wherein said circuit means includes limit means responsive to the ionization current for producing one indication when the ionization current is below a predetermined value and a second indication when the ionization exceeds the predetermined value.
Claim 22
Dependent Claim
41 words
An apparatus as in claim 16, wherein said sensing means includes a radiation detector in the chamber and exposed to radiation from the radioactive source means so as to have the output vary in response to dust accumulation in the chamber.
Claim 23
Dependent Claim
52 words
An apparatus as in claim 16, wherein said sensing means includes auxiliary electrode means mounted in said chamber and insulating means separating said auxiliary electrode means from said pair of electrode means so that dust varies the resistance between said auxiliary electrode means and said one of said pair of electrode means.
Claim 24
Dependent Claim
15 words
An apparatus as in claim 22, wherein said auxiliary electrode means includes said radioactive source.
Claim 25
Dependent Claim
87 words
An apparatus as in claim 22, wherein said circuit means connects said auxiliary electrode means and one of said pair of electrode means so as to exhibit equal potentials, and wherein said circuit means measures the difference in partial currents through said auxiliary electrode means and one of said pair of electrode means so as to produce a first indication when the difference between the partial currents exceeds a certain value and a second indication when the difference in partial currents is less than the certain value.
Claim 26
Dependent Claim
21 words
An apparatus as in claim 24, wherein the threshold value is a difference of the two partial currents equal to zero.
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) | 1977-03-04 | 1977-09-03 | 1978-03-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-03-04 | 1981-09-03 | 1982-03-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-03-04 | 1985-09-03 | 1986-03-05 | $7700.00 | Window Closed / Lapsed |