US3560737A - Combustion products detector using a radioactive source and detector - Google Patents

Combustion products detector using a radioactive source and detector Download PDF

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Publication number
US3560737A
US3560737A US657826A US3560737DA US3560737A US 3560737 A US3560737 A US 3560737A US 657826 A US657826 A US 657826A US 3560737D A US3560737D A US 3560737DA US 3560737 A US3560737 A US 3560737A
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United States
Prior art keywords
cathode
anode
radius
radioactive source
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Expired - Lifetime
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US657826A
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English (en)
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John D Skildum
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Honeywell Inc
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Honeywell Inc
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/62—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode
    • G01N27/64—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber
    • G01N27/66—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating the ionisation of gases, e.g. aerosols; by investigating electric discharges, e.g. emission of cathode using wave or particle radiation to ionise a gas, e.g. in an ionisation chamber and measuring current or voltage
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G08B17/113—Constructional details

Definitions

  • FIG. I is a sectional view of the detector unit taken along the line ll of FIG. 2;
  • FIG. 2 is a plan view of the detector unit
  • FIG. 3 is a side elevational view of the detector unit with a portion of the outer shielding electrode broken away;
  • FIG. 4 is a schematic circuit diagram of preferred electrical connections which may be made to the detector unit.
  • the invention consists in the preferred embodiment essentially of an anode 10 carrying a beta source 11, such as Nithu 63, and a cathode l2.
  • a beta source 11 such as Nithu 63
  • a cathode l2 Radioactive beta sources other than Ni such as tritium and the like, may also be used.
  • Ni is preferred and may be conveniently electroplated on anode 10 in the fonn of a thin coating as shown.
  • anode 10 takes the form of a pin as shown and cathode IZtakesthe form of a cylinder which may be cup-shaped as shown. Both electrodes are carried by an insulating board 13 and may be connected thereto by various standard means.
  • the electrodes are spaced to provide a critical interelectrode space 14 wherein combustion products may be detected as they diffuse through openings established common practice to use the aforementioned double chamber arrangement in order to overcome the inherent sensitivity of such detectors to nonnal changes in ambient pressure, temperature, humidity and rate of flow of the gasefo'us sample entering the chambers.
  • Such arrangements are electronically complicated and costly. Furthermormfihese detectors tend to respond with false alarms to unexpectedly rapid variations in normal ambient conditions.
  • the SUMMARY chamber device including a single radioactive source is used for bringing about the ionization wherein the radioactive source is particularly characterized in that it provides substantially only beta particles.
  • the source is carried by one of the electrodes, preferably the anode, and the electrodes are critically positionedto provide'aninterelectrode space or distance therebetween which is slightly less than the maximum range of the higher energy beta particles but in excess of the range of the lower energy beta particles. Since there are relatively few higher energy beta particles, a minor number of the beta particles emitted traverse the interelectrode space to contact the opposing electrode whereas most of the beta particles do not.
  • radioactive sources which emit substantially only beta particles be used and the spacing between the electrodes be such that the majority of the beta particles emitted from the source carried by one of the electrodes, such as anode l0 fail to traverse the interelectrode space 14 while a minority of the beta particles actually traverse space 14 and reach the other electrode, such as cathode 12.
  • Such an arrangement is not practical with other radioactive sources such as alpha and gamma sources.
  • the critical interelectrode spacing in accordance with this invention has been determined for radioactive beta sources generally.
  • the interelectrode spacing must correspond to less than about the maximum range of the higher energy beta particles emitted by the source in air at standard conditions and greater than about one and one-half times the half-thickness range of the beta particles emitted by the source in air at standard conditions.
  • the spacing limitation is one which is greater than about I cm. but less than about 5.3 cm. with about 3 cm. being more preferred.
  • the geometry is cylindrical having the pin-shaped anode 10 carrying the beta source axially aligned within the cylindrical cup-shaped cathode 12.
  • This configuration is used to provide a strong field near the anode for affecting ionized negative charge carriers and a weak field near the cathode for affecting positive charge carriers whereby recombination effects are minimized in air in the absence of combustion products and a stable current is attained during operation.
  • this configuration provides field effects which are insufficient to collect charge carriers before recombination occurs and the current decreases.
  • this configuration provides a compact symmetrical detector.
  • detectors having the preferred cylindrical configuration including the radioactive source of Ni the following design parameters provide an improved detector capable of operating in or near current saturation with low voltages (below about 30 volts) applied between the anode and cathode ambient air without the presence of combustion products:
  • anode 10, cathode l2 and interelectrode space 14 may be electrically shielded from stray field effects.
  • the detector shown in H68. 1, 2 and 3 includes a second cylindrical cup-shaped electrode 16 within which anode l and cathode 12 are axially aligned. Electrode 16 includes a plurality of openings 16a on its sides and bottom as shown to allow access of combustion products, ambient air and the like which diffuse therethrough and through the cathode openings 12a into the sensitive interelectrode space. Cylindrical electrode 16 is positioned close to cathode 12 in order to provide a strong field between electrode 16 and cathode 12. For the preferred cylindrical configuration shown, a practical spacing has been found to correspond to the one established when the radius of the cylindrical electrode 16 is greater than the radius of cathode 12 but less than double the radius of cathode 12.
  • electrode 16 may be carried by insulating board 13 in the same manner as cathode 12.
  • Board 13 is enclosed in a housing 17 and held together by bolts 18.
  • lnsulating ring 19 is included in housing 17.
  • housing 17 is in electrical contact with electrode 16 and is therefore maintained at the same potential.
  • space 20 which may be used to house the electronic circuitry for the detector. Electrically shielded circuitry is important for stable operation'at the preferred low current involved.
  • the circuitry may take the form of solid state components (not shown) mounted directly on the insulating board 13. Electrode contacts 10b, 12b and 16b are shown extending through board 13 for connection to the electrical circuitry. Additional bolts 21 may be used for mounting the detector on the wall or ceiling of a building.
  • the detector electrodes which are shown schematically, are connected into an illustrative circuit.
  • the basic device consisting of anode l0 and cathode 12 may be used in any of the many typical circuits known in the art for this type of detector, the type of arrangement shown as been found to be desirable in that preferred operating potentials may be conveniently applied to electrodes 10, 12 and 16.
  • the circuit includes potential source means such as seriesconnected batteries 24 and 26.
  • the positive side of battery 24 is connected to a suitable reference potential, such as ground, and to electrode 16 while the negative side of battery 26 is connected to cathode 12.
  • Anode 10 is connected through the micromicroammeter 27 to a point intermediate batteries 24 and 26 resulting in an applied potential at anode 10 which is positive with respect to cathode 12 but slightly negative with respect to the reference potential and electrode 16.
  • a micromicroammeter is shown for convenience in the FIG. but other current sensing means including various arrangements for amplification may be utilized as will be obvious to those familiar with this art.
  • a selected current is set up between anode 10 and cathode 12, which may be at or nearcurrent saturation.
  • voltages of less than 30 volts have been found to be adequate'and are in fact desired in practice.
  • Current flows between the anode and cathode due to the ionization of the air in the interelectrode space by the beta particles emitted from the source carried by anode 10. Upon the entrance of combustion products into the interelectrode space, the current decreases in accordance with principles already known in the art.
  • An apparatus for detecting products of combustion of the type where unidirectional potential is impressed across the electrodes comprising:
  • anode and cathode electrode defining an interelectrode space and arranged to provide access into said in terelectrode space for products of combustion, said anode and cathode adapted to be connected to a source of unidirectional potential;
  • a radioactive source of substantially only bcta particles below about l.6 mC carried by one of said electrodes for emitting beta particles into said interelectrode space to produce current carriers between said electrodes;
  • said interelectrode space dimensionally corresponds to less than the maximum range of the higher energy beta particles emitted from said source at said one electrode and greater than one and one-half times the half-thickness range of the beta particles emitted from said source at said one electrode.
  • said anode is in the form of a pin
  • said radioactive source is a coating on said anode
  • said cathode is in the fdrm of a cylinder
  • said supporting means supports said pin substantially coaxially inside said cylinder.
  • said radioactive source is Ni and said interelectrode space is greater than about I cm and less than about 5.3 cm.
  • support means supports said pin anode and said cylindrical cathode substantiallycoaxially within said shielding electrode.
  • the radius of said pin anode is greater than about 2 mm.
  • the radius of said cylindrical cathode is greater than about I cm. and less than about 5.3 cm.; said radioactive source is between about 0.05 mC and about l.5 mC of Ni said shielding electrode is in the form of a cylinder having a radius greater than the radius of 'said cylindrical cathode and less than double the radius of said cylindrical cathode; and
  • said apparatus is adapted for substantially stable operation at about current saturation in air with an applied voltage between said anode and cathode of less than about 30 volts.
  • An apparatus for detecting products of combustion of the type where unidirectional potential is impressed across the electrodes comprising:
  • an anode in pin shape having a radius from about 2 mm to about 4.5 mm, said anode having a coating of Ni for a radioactive source of a strength of 0.05 mC to 1.6 mC;
  • a cathode in generally cylindrical form having a radius of from about 1 em. up to about 5.3 cm.;
  • said anode and said cathode adapted to be connected to a unidirectional potential whereby said apparatus is adapted to operate substantially at an applied voltage between the anode and cathode of less than about 30 volts.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Health & Medical Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Toxicology (AREA)
  • Electrochemistry (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
  • Prostheses (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Measurement Of Radiation (AREA)
US657826A 1967-08-02 1967-08-02 Combustion products detector using a radioactive source and detector Expired - Lifetime US3560737A (en)

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US65782667A 1967-08-02 1967-08-02

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US657826A Expired - Lifetime US3560737A (en) 1967-08-02 1967-08-02 Combustion products detector using a radioactive source and detector

Country Status (6)

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US (1) US3560737A (de)
BE (1) BE718911A (de)
DE (1) DE1773949A1 (de)
FR (1) FR1575343A (de)
GB (1) GB1228800A (de)
NL (1) NL6810468A (de)

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3693009A (en) * 1968-12-24 1972-09-19 Nittan Co Ltd Ionization smoke detecting device
US3731093A (en) * 1968-06-18 1973-05-01 Cerberus Ag Ionization fire alarm with wind screen
US3767917A (en) * 1970-07-23 1973-10-23 Cerberus Ag Ionizing-type fire alarm sensor
US3935465A (en) * 1973-04-24 1976-01-27 Geba-Gesellschaft Fuer Elektronische Brandmeldeanlagen Mbh Ionization analyzing air pollution, smoke and fire alarm device
US4021671A (en) * 1975-07-07 1977-05-03 Gulf & Western Manufacturing Company (Systems) Ionization detector
US4025794A (en) * 1974-10-22 1977-05-24 James Ephraim Lovelock Ionization detectors with iron-55 as a radioactive source
US4044263A (en) * 1975-01-28 1977-08-23 Walter Kidde & Company, Inc. Ionization dual-zone static detector having single radioactive source
US4185197A (en) * 1978-01-13 1980-01-22 General Electric Company Arrangement for inhibiting the effect of extraneous electric fields on an improved ionization smoke detector
FR2438841A1 (fr) * 1978-10-13 1980-05-09 Commissariat Energie Atomique Capteur ionique pour detecteur d'incendie
WO1985001111A1 (en) * 1983-09-05 1985-03-14 Nohmi Bosai Kogyo Kabushiki Kaisha Heat-resistant casing for ionization type smoke sensor
EP0221770A2 (de) * 1985-10-31 1987-05-13 Gent Limited Ionisationsdetektionskammer
US4864141A (en) * 1986-02-25 1989-09-05 Jacques Lewiner Smoke detector with ionization chamber
JP2008014947A (ja) * 2006-07-06 2008-01-24 General Electric Co <Ge> 内部漏洩検出を備えたＨｅ−３中性子比例計数管及び関連する方法
US20080210839A1 (en) * 2006-11-15 2008-09-04 Klapp Charles R Smoke detector recessed box

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2908819A (en) * 1955-06-13 1959-10-13 Phillips Petroleum Co Apparatus for measuring properties of gases
US2990492A (en) * 1958-10-24 1961-06-27 Gen Electric Electric discharge device
US3185845A (en) * 1961-02-15 1965-05-25 Continental Oil Co Method of and apparatus for analyzing chemical compounds
US3271756A (en) * 1960-03-22 1966-09-06 Harold J Burke Method and apparatus for detecting a hazardous condition

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2908819A (en) * 1955-06-13 1959-10-13 Phillips Petroleum Co Apparatus for measuring properties of gases
US2990492A (en) * 1958-10-24 1961-06-27 Gen Electric Electric discharge device
US3271756A (en) * 1960-03-22 1966-09-06 Harold J Burke Method and apparatus for detecting a hazardous condition
US3185845A (en) * 1961-02-15 1965-05-25 Continental Oil Co Method of and apparatus for analyzing chemical compounds

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3731093A (en) * 1968-06-18 1973-05-01 Cerberus Ag Ionization fire alarm with wind screen
US3693009A (en) * 1968-12-24 1972-09-19 Nittan Co Ltd Ionization smoke detecting device
US3767917A (en) * 1970-07-23 1973-10-23 Cerberus Ag Ionizing-type fire alarm sensor
US3935465A (en) * 1973-04-24 1976-01-27 Geba-Gesellschaft Fuer Elektronische Brandmeldeanlagen Mbh Ionization analyzing air pollution, smoke and fire alarm device
US4025794A (en) * 1974-10-22 1977-05-24 James Ephraim Lovelock Ionization detectors with iron-55 as a radioactive source
US4044263A (en) * 1975-01-28 1977-08-23 Walter Kidde & Company, Inc. Ionization dual-zone static detector having single radioactive source
US4021671A (en) * 1975-07-07 1977-05-03 Gulf & Western Manufacturing Company (Systems) Ionization detector
US4185197A (en) * 1978-01-13 1980-01-22 General Electric Company Arrangement for inhibiting the effect of extraneous electric fields on an improved ionization smoke detector
FR2438841A1 (fr) * 1978-10-13 1980-05-09 Commissariat Energie Atomique Capteur ionique pour detecteur d'incendie
WO1985001111A1 (en) * 1983-09-05 1985-03-14 Nohmi Bosai Kogyo Kabushiki Kaisha Heat-resistant casing for ionization type smoke sensor
US4853544A (en) * 1983-09-05 1989-08-01 Katsumasa Inamura Heat-resistant case for an ionization-type smoke detector and method of making the same
EP0221770A2 (de) * 1985-10-31 1987-05-13 Gent Limited Ionisationsdetektionskammer
EP0221770A3 (en) * 1985-10-31 1988-08-24 Gent Limited Ionisation detection chamber
US4864141A (en) * 1986-02-25 1989-09-05 Jacques Lewiner Smoke detector with ionization chamber
JP2008014947A (ja) * 2006-07-06 2008-01-24 General Electric Co <Ge> 内部漏洩検出を備えたＨｅ−３中性子比例計数管及び関連する方法
US20080265171A1 (en) * 2006-07-06 2008-10-30 General Electric Company He-3 neutron proportional counter with internal leakage detection and related method
US7456411B2 (en) * 2006-07-06 2008-11-25 General Electric Company He-3 neutron proportional counter with internal leakage detection and related method
US20080210839A1 (en) * 2006-11-15 2008-09-04 Klapp Charles R Smoke detector recessed box

Also Published As

Publication number Publication date
DE1773949A1 (de) 1971-11-25
BE718911A (de) 1969-01-16
NL6810468A (de) 1969-02-04
FR1575343A (de) 1969-07-18
GB1228800A (de) 1971-04-21

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