US3731093A - Ionization fire alarm with wind screen - Google Patents

Ionization fire alarm with wind screen Download PDF

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Publication number
US3731093A
US3731093A US00131106A US3731093DA US3731093A US 3731093 A US3731093 A US 3731093A US 00131106 A US00131106 A US 00131106A US 3731093D A US3731093D A US 3731093DA US 3731093 A US3731093 A US 3731093A
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United States
Prior art keywords
ionization
sheathing
chamber
fire alarm
aperture
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
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US00131106A
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English (en)
Inventor
A Scheidweiler
P Muller
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Cerberus AG
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Cerberus AG
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    • 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
    • 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
    • G08B25/00—Alarm systems in which the location of the alarm condition is signalled to a central station, e.g. fire or police telegraphic systems

Definitions

  • Patent 1 [111 warms Scheidweiler et al. 1 May 1, W73
  • Appl' 13l106 chamber means, across a pair of conductors supplied Related US Application Data by a direct-current voltage of less than 60 volts.
  • the ionization chamber has a sheathing means serving as a Continuation-impart of Sen June wind screen for reducing the velocity of air flow 1969, abandoned within the chamber such that circulation of air within the chamber has substantially no effect upon the [30] Foreign Application Priority Data ionization current.
  • the sheathing means preferably in- June 18 1968 Switzerland ..9035/68 eludes an Outer and inner portion with the inner face of the outer portion having a geometric shape 52 US.
  • This invention generally relates to fire alarms and particularly concerns low-voltage fire alarms of the ionization type which comprise at least one ionization chamber, the interior of which is in communication with the ambient air, at least a source of ionizing radiation and two electrodes, one of which electrodes may be constructed as a wall of the chamber, and a sheathing for reducing the speed of the ambient air flow into the interior of the chamber itself.
  • Ionization fire alarms serving to detect the presence of combustion aerosols in the ambient air generally comprise at least one ionization chamber which includes a radioactive substance for ionizing the air within the chamber.
  • a voltage is applied between two electrodes within the chamber or between a single electrode and the chamber wall such that a flow of electric current arising from a flow of ions within the chamber occurs between the electrodes. Accordingly, upon the entrance of aerosols or other particles such as smoke or dust into the chamber, the ionization current will be altered.
  • Swiss patent specifications No. 297,463 and 355,380 describe an arrangement in which such an ionization chamber is connected in series with a resistor.
  • the change of current in the ionization chamber occurring upon the appearance of aerosols or other particles within the chamber brings about a change in potential at an electrode, such potential change being appropriately amplified and subsequently employed so as to give an alarm.
  • a further object of the instant invention is to provide a novel construction of an ionization fire alarm which is protected by screening devices specifically provided for he purpose of ensuring that the ionization current within the chamber is not appreciably affected by air flowing through the chamber.
  • Still a further extremely important object of the present invention is the provision of a novel construction of ionization fire alarm operating at low direct-current voltages, the supply voltage being less than volts,- resulting in reduced field strength conditions within the ionization chamber and thus reduced velocity of the ions, whereby to safeguard against undesirable affects upon ion mobility by wind currents entering the ionization chamber there is provided novel screening which minimizes the possible adverse affects which such wind current could otherwise have upon movement of the ions between the electrodes of the ionization chamber.
  • a low directcurrent voltage ionization fire alarm comprising at least one ionization chamber to which chamber the external air has access and which includes at least a radioactive substance and two electrodes.
  • This ionization chamber is connected in series with a resistance element, preferably defining a reference chamber, across two conductor lines supplied by a direct-current voltage of less than 60 volts.
  • the terminal point of the ionization chamber and the resistance element is connected to the gate electrode of a field-effect transistor.
  • the novel ionization fire alarm of the instant invention further has a sheathing provided -at the ionization chamber for reducing the velocity of air flow within the chamber,
  • such sheathing comprising an outer and an inner portion which are separable from one another, the inner surface of the outer portion having a geometric form or shape similar to that of the outer surface of the inner portion, the two surfaces being disposed substantially parallel with one another.
  • Both the inner and the outer sheathing portions are pierced by at least one aperture, the aperture or apertures in the outer portion being displaced with respect to the aperture or apertures in the inner portion such that the lateral separation between the margins or the edges of each aperture in the outer sheathing portion and each aperture in the inner sheathing portion is greater than the separation between the two sheathing portions themselves.
  • FIG. 1 depicts an axial cross-section through an ionization chamber of cylindrical form in accordance with the instant invention
  • FIG. 2 depicts a partially sectional side elevational view of a novel ionization of the type depicted in FIG.
  • FIG. 3 depicts a cross-section taken through an ionization chamber of more complex form forming a rough approximation to the hemispherical in accordance with the instant invention
  • FIG. 4 is a partially cut-away perspective view of the ionization chamber of FIG. 3;
  • FIG. 5 depicts an ionization chamber built into a surrounding structure
  • FIG. 6 is a circuit diagram of typical circuitry of a low direct-current voltage transistorized ionization fire alarm system employing the inventive wind screening structure and serving to explain the general environment in which the concepts of the invention are particularly useful.
  • an ionization chamber having a cylindrical sensitive space or measuring volume 1.
  • An insulating base plate 2 carries an inner electrode 3 and an outer electrode 4, the outer electrode 4 preferably being of mesh form.
  • the sensitive space or measuring volume 1 is surrounded by a sheathing consisting of two portions; an inner sheathing portion 5 which, in turn, is surrounded by an outer sheathing portion 6.
  • the two sheathing portions surround the measuring chamber up to the fixing or supporting plane 7 thereof.
  • Portions 8, 9 of radioactive material are provided in the interior of the chamber. The ionizing radiation emitted by such radioactive material serves to ionize the air in the space between the two electrodes 3 and 4 and gives rise to an electric current between such electrodes.
  • the outer sheathing portion 6 has a geometrical form or shape similar to that of the inner sheathing portion 5 such that the separation between the two sheathing portions is approximately the same at all places.
  • the air to be investigated or monitored may enter through apertures 10 into the interspace between the two sheathing portions and thence through further apertures 11 and 12 provided in the inner sheathing portion 5 into the interior of the chamber.
  • the separation between the two sheathing portions 5 and 6 is small as compared with the dimensions of the chamber.
  • the apertures in the outer sheathing portion are displaced with respect to the apertures in the inner sheathing portion such that the separation of the margins or edges of the access apertures is greater than the separation between the two sheathing portions. Accordingly, by adhering to these measures the flow of air into the ionization fire alarm is so greatly retarded that it only has a low velocity as it enters into the measuring space or volume.
  • FIGS. 3 and 4 depict an ionization fire alarm of a somewhat more complex form than that depicted in FIGS. 1 and 2, such form being a rough approximation to the hemispherical.
  • the measuring volume 13 is again surrounded by an inner sheathing portion 14 which, in turn, is surrounded at least as far as the fixing or supporting plane 16 by an outer sheathing portion 15 of similar geometrical form or shape such that the separation between the internal and external sheathing portions is approximately constant.
  • An inner electrode 18 passes through an insulating base plate 17, inner electrode 18 carrying a radioactive substance 19.
  • the wall of the inner sheathing portion 14 acts as the second electrode in this embodiment.
  • the air to be supervised or monitored can enter into the measurement space or volume through access apertures 20 provided in the outer sheathing portion and through access apertures 21 and 22 provided in the inner sheathing portion.
  • the arrangement or disposition of the access apertures in relation to one another is again importantly such that even with high flow velocity of the ambient air, the velocity of air flow within the chamber itself is small.
  • the access apertures are displaced in relation to one another such that it is not possible to draw a straight line through an aperture n the outer sheathing portion and through any aperture in the inner sheathing portion. This is ensured by placing the apertures in the inner sheathing portion and in the outer sheathing portion on different surfaces which are not parallel with one another, but which rather includes an angle between them.
  • apertures 22 are preferably constructed as wire grids.
  • the access apertures provided in the outer sheathing portion are inclined to the axis of the alarm itself, here a vertical axis, by an angle which lies between 30 and 60, such angle in the illustrated embodiment being 45. It is thus ensured that the ionization chamber has sufficient sensitivity and that such sensitivity remains as uniform as possible for both vertical and horizontal air flows.
  • the sheathing may consist of a plurality of appropriately assembled parts.
  • the inner and outer sheathing portions are mechanically separate from one another and the outer portion is preferably separable or removable.
  • the apertures in the inner sheathing portion preferably and advantageously consist either wholly or in part of grids.
  • a further ionization chamber operating as a reference chamber closed against the external air may be situated on the other side of the base plate 2 or 17, as generally indicated by reference character 40, as might be other components and electrical circuits.
  • the other parts of the circuit of the ionization fire alarm are normally combined with the measuring chamber into a single compact unit.
  • the mounting plane for the two sheath portion would lie approximately in the plane of the insulating base plate 2 or 17.
  • One of the two sheath portions for the measuring chamber can, in this instance, also serve as a casing for the circuit components.
  • FIG. 5 depicts a further embodiment of the instant invention in which the outer portion of the sheathing for the measuring chamber is formed as a part of a mounting base 28 for mounting the fire alarm.
  • the measuring chamber here consists of the base plate 24, the electrode 25 with the radioactive substance 26, and the inner sheath portion 27 which here acts as the second electrode.
  • the access aperture in the outer sheath portion is considered as being formed by the circular aperture 29 in the base 28 which, so as to further reduce the effect of air currents, may be provided with a non-illustrated cover pierced by small apertures.
  • the inner apertures 30 are displaced from the aperture in the base by more than the separation between the inner wall of the base and the inner sheathing portion.
  • the outer and inner sheathing portions are separable from one another, which can be easily accomplished, for instance, if the outer sheathing portion is removably clamped or otherwise conveniently attached for instance to the support or base plate, or the support surface by way of example.
  • This is advantageous since the removable feature of the sheathing portions allows for convenient cleaning of the interspace between such portions which may become deposited with dust particles and other contaminants. Cleaning can therefore be easily performed from time to time by simply dismantling the removable outer sheathing portion.
  • FIG. 6 schematically depicts a simple embodiment of ionization fire alarm
  • the ionization or measuring chamber is electrically coupled at its inner electrode 52 with the negative pole of the operating voltage voltage U, through the agency of the resistor III which conceptually may be considered to define a reference chamber and the conductor line we and at its chamber housing l is electrically coupled with the positive pole of such operating voltage U through the agency of the conductor line wL-This operating voltage is a direct-current voltage of less than 60 volts.
  • the ionization chamber 110 only schematically illustrated in FIG. 6, can embody any of the heretofore disclosed constructions of ionization chambers discussed in conjunction with FIGS.
  • the inner sheathing 102 and the outer sheathing 103 which may conform to the constructions of any of the heretofore discussed embodiments.
  • a radioactive source 53 similar to the arrangement of FIGS. 3, 4 and 5.
  • a plurality of radioactive sources such as shown for instance in the embodiment of FIGS. 1 and 2.
  • the voltage U across the measuring or ionization chamber 110 is, at the same time, the gate voltage for a suitable semiconductor element, namely the field-effect transistor 120 providing a sensing or indicating means which senses voltage changes across the electrodes 51 and 52 of the ionization chamber 110.
  • This voltage U is chosen such that the field-effect transistor 120 in its quiescent state blocks current flow, that is to say, at the working resistor 130 there is no voltage drop. Moreover, it should be appreciated that in the absence of smoke and combustion aerosols the voltage across the ionization chamber 110 is advantageously of a magnitude smaller than volts. The gate-controlled rectifier 140 is therefore likewise blocked and the relay 150 is not energized. Now, if smoke or combustion gases penetrate into the measuring or ionization chamber 110 then the chamber voltage U increases and upon exceeding a predetermined threshold triggers ignition of the controlled rectifier 140, whereby the relay 150 triggers a suitable alarm. Triggering of the alarm can be carried out in any appropriate manner, as for instance shown and described in commonly assigned U.S. Pat. No. 3,233,100 of Thomas Lampart, entitled Determining Presence of Aerosols ln Gases," and granted Feb. 1, 1966. In this instance, the field-effect transistor 120 operates both as a threshold device as well as also as an amplifier element.
  • An ionization fire alarm comprising at least one ionization chamber to which the external air has access, said ionization chamber including at least one radioactive substance and two electrodes, said ionization chamber being connected in series with a resistance element and across two conductor lines supplied by a D.C.
  • said ionization chamber further including sheathing means for reducing the velocity of air flow within said ionization chamber, said sheathing means comprising a respective outer and inner sheathing portion, said outer and said inner sheathing portions being separable from each other, the inner surface of said outer portion having a geometric form substantially similar to that of the outer surface of said inner portion, said two surfaces being disposed in spaced relationship with regard to one another, said inner and outer sheathing portions each being pierced by at least one respective aperture, said aperture in said outer portion is displaced with respect to said aperture in said inner portion such that said agertures are dis osed in a non-overlappin relations 1p to provide a ortuous air path of substan rally nonlinear characteristics through said ionization chamber thereby greatly reducing undesirable wind effects on the ionization current in said ionization chamber.
  • Electrodes in said ionization chamber are supplied by a voltage which is less than 20 volts D.C.

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  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Health & Medical Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Electrochemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Toxicology (AREA)
  • Biochemistry (AREA)
  • General Health & Medical Sciences (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US00131106A 1968-06-18 1971-04-05 Ionization fire alarm with wind screen Expired - Lifetime US3731093A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH903568A CH475614A (de) 1968-06-18 1968-06-18 Ionisationsfeuermelder

Publications (1)

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US3731093A true US3731093A (en) 1973-05-01

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Application Number Title Priority Date Filing Date
US00131106A Expired - Lifetime US3731093A (en) 1968-06-18 1971-04-05 Ionization fire alarm with wind screen

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US (1) US3731093A (xx)
BE (1) BE734060A (xx)
CH (1) CH475614A (xx)
DE (1) DE1928874B2 (xx)
DK (1) DK125938B (xx)
FR (1) FR2011126A1 (xx)
GB (1) GB1217792A (xx)
HK (1) HK20378A (xx)
IL (1) IL32330A (xx)
NL (1) NL164407C (xx)
SE (1) SE340971B (xx)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3903419A (en) * 1973-04-20 1975-09-02 Fire Alert Company Combustion products detector assembly and method of operation
US3908957A (en) * 1973-04-17 1975-09-30 Cerberus Ag Ionization-type fire sensor
DE2516860A1 (de) * 1974-04-18 1975-10-30 Hochiki Co Nach dem ionisationsprinzip arbeitender rauchfuehler
DE2520929A1 (de) * 1974-05-10 1975-11-27 Gen Signal Corp Ionisations-feuerdetektor
US4044263A (en) * 1975-01-28 1977-08-23 Walter Kidde & Company, Inc. Ionization dual-zone static detector having single radioactive source
US4439683A (en) * 1981-02-11 1984-03-27 General Signal Corporation Ionization smoke detector
US4469953A (en) * 1982-02-02 1984-09-04 Nittan Company, Limited Combination ionization and photoelectric smoke detector
US4529976A (en) * 1982-10-29 1985-07-16 Frederick M. Jameson Smoke detector with masking shield
US4864141A (en) * 1986-02-25 1989-09-05 Jacques Lewiner Smoke detector with ionization chamber
US5485144A (en) * 1993-05-07 1996-01-16 Pittway Corporation Compensated ionization sensor

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01102991U (xx) * 1987-12-26 1989-07-12

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3353170A (en) * 1962-11-19 1967-11-14 Cerberus Ag Ionization fire alarm system
US3514603A (en) * 1966-12-22 1970-05-26 Johnson Service Co Ionization chamber detection apparatus having a low voltage source means
US3560737A (en) * 1967-08-02 1971-02-02 Honeywell Inc Combustion products detector using a radioactive source and detector

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3353170A (en) * 1962-11-19 1967-11-14 Cerberus Ag Ionization fire alarm system
US3514603A (en) * 1966-12-22 1970-05-26 Johnson Service Co Ionization chamber detection apparatus having a low voltage source means
US3560737A (en) * 1967-08-02 1971-02-02 Honeywell Inc Combustion products detector using a radioactive source and detector

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3908957A (en) * 1973-04-17 1975-09-30 Cerberus Ag Ionization-type fire sensor
US3903419A (en) * 1973-04-20 1975-09-02 Fire Alert Company Combustion products detector assembly and method of operation
DE2516860A1 (de) * 1974-04-18 1975-10-30 Hochiki Co Nach dem ionisationsprinzip arbeitender rauchfuehler
DE2520929A1 (de) * 1974-05-10 1975-11-27 Gen Signal Corp Ionisations-feuerdetektor
US3959788A (en) * 1974-05-10 1976-05-25 General Signal Corporation Ionization-type fire detector
US4044263A (en) * 1975-01-28 1977-08-23 Walter Kidde & Company, Inc. Ionization dual-zone static detector having single radioactive source
US4439683A (en) * 1981-02-11 1984-03-27 General Signal Corporation Ionization smoke detector
US4469953A (en) * 1982-02-02 1984-09-04 Nittan Company, Limited Combination ionization and photoelectric smoke detector
US4529976A (en) * 1982-10-29 1985-07-16 Frederick M. Jameson Smoke detector with masking shield
US4864141A (en) * 1986-02-25 1989-09-05 Jacques Lewiner Smoke detector with ionization chamber
US5485144A (en) * 1993-05-07 1996-01-16 Pittway Corporation Compensated ionization sensor

Also Published As

Publication number Publication date
IL32330A0 (en) 1969-08-27
HK20378A (en) 1978-04-20
SE340971B (xx) 1971-12-06
DE1928874A1 (de) 1970-01-02
IL32330A (en) 1972-04-27
DE1928874B2 (de) 1978-03-09
BE734060A (xx) 1969-11-17
CH475614A (de) 1969-07-15
NL164407B (nl) 1980-07-15
NL6909253A (xx) 1969-12-22
DK125938B (da) 1973-05-21
GB1217792A (en) 1970-12-31
FR2011126A1 (xx) 1970-02-27
NL164407C (nl) 1980-12-15

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