US3792279A - Ionization smoke detector - Google Patents

Ionization smoke detector Download PDF

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Publication number
US3792279A
US3792279A US00193901A US3792279DA US3792279A US 3792279 A US3792279 A US 3792279A US 00193901 A US00193901 A US 00193901A US 3792279D A US3792279D A US 3792279DA US 3792279 A US3792279 A US 3792279A
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US
United States
Prior art keywords
source
ionization
electrodes
chamber
smoke detector
Prior art date
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
Application number
US00193901A
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English (en)
Inventor
K Sasaki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nittan Co Ltd
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Nittan Co Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Nittan Co Ltd filed Critical Nittan Co Ltd
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Publication of US3792279A publication Critical patent/US3792279A/en
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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
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T7/00—Details of radiation-measuring instruments
    • G01T7/12—Provision for actuation of an alarm
    • G01T7/125—Alarm- or controlling circuits using ionisation chambers, proportional counters or Geiger-Mueller tubes, also functioning as UV detectors
    • 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

Definitions

  • An ionization smoke detector of the type concerned includes a closed ionization chamber and an open ionization chamber each having a pair of electrodes and a radioactive source and connected in series between a pair of terminals to be connected to a central unit, a field effect transistor (hereinafter referred to as FET) having a gate electrode connected to the connection point of both ionization chambers and a source-to-drain path connected between both terminals.
  • FET field effect transistor
  • a relay element such as silicon controlled rectifier (hereinafter referred to as SCR) has a control electrode connected to the source electrode of the FET and a main conduction path connected between both terminals. A specific operation voltage is applied between both terminals from the central unit in the normal monitoring condition.
  • the ionization current flowing in the open ionization chamber is reduced and thereby the impedance of the open ionization chamber is increased to raise the potential at the junction point of both ionization chambers and, accordingly, the gate potential of the F ET.
  • an object of this invention is to propose an ionization smoke detector having aninexpensive and strongly built sensitivity control which affords improved stability.
  • this object is attained by inserting a series connection of a plurality of diodes in series with the source-to-drain path of the FET.
  • FIG. 1 is a schematic circuit diagram representing an ionization smoke detector including a sensitivity controlaccording to prior art
  • FIG. 2 is a schematic circuit diagram representing an ionization smoke detector including a sensitivity control according to this invention.
  • the ionization smoke detector includes a closed ionization chamber 10 having a pair of electrodes 1 l and 12 and a radio-active source 13 and an open ionization chamber 20 having a pair of electrodes 21 and 22 and a radioactive source 23.
  • Both the ionization chambers 10 and 20 are connected in series between a pair of terminals l and 2 which are to be connected to a central unit (not shown).
  • the connection point 3 of both ionization chambers is connected to the gate electrode G of an FET 4 having a drain electrode D connected to the terminal 1 and a source electrode S connected through a resistive'element of a potentiometer 8 and a load resistor 5 to the terminal 2.
  • the movable contact of the potentiometer 8 is connected to the control electrode of an SCR 6 whose main conduction path is connected between both terminals 1 and 2.
  • the control electrode of the SCR 6 is also connected through a leakage resistor 7 to terminal 2.
  • the sensitivity of the detector can be controlled by moving the movable contact'9 of the potentiometer 8 to control the voltage to be applied to the control electrode of the SCR 6.
  • mechanical contact 9 is often defective or makes improper contact and, thus, reduces the reliability of the device.
  • the circuit is the same as that of FIG. 1 except that a series connection of a plurality of diodes 31, 32, 33, is inserted in place of the potentiometer 8 of FIG. 1.
  • Terminals 41, 42 are respectively led out from the connection points between the respective diodes and a contact 9 which is connected to the control electrode of the SCR 6 is selectively connected to one of the terminals 41, 42,
  • the contact 9 may be constructed as a movable change-over contact, but it is preferable to fixedly connect it to one terminal which is previously selected in accordance with its situation, by means of screwing or soldering, in order to prevent improper'contact.
  • Each of the diodes exhibits a voltage drop of about 0.5 volts, for example, and this value is maintained almost constant in spite of variations in the current flowing therethrough. Therefore, the terminals 41, 42
  • An ionization smoke detector comprising at least one open ionization chamber including a pair of electrodes and a radioactive source, means for applying a voltage to said electrodes, a field effect transister having gate, drain and source electrodes, a connection between one of said chamber electrodes and said gate electrode, a plurality of series connected diodes fortrance of smoke into said chamber.

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  • General Physics & Mathematics (AREA)
  • Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Toxicology (AREA)
  • Business, Economics & Management (AREA)
  • General Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • Pathology (AREA)
  • Immunology (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • Emergency Management (AREA)
  • High Energy & Nuclear Physics (AREA)
  • Molecular Biology (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US00193901A 1970-11-19 1971-10-29 Ionization smoke detector Expired - Lifetime US3792279A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP1970114352U JPS4940290Y1 (enrdf_load_stackoverflow) 1970-11-19 1970-11-19

Publications (1)

Publication Number Publication Date
US3792279A true US3792279A (en) 1974-02-12

Family

ID=14635583

Family Applications (1)

Application Number Title Priority Date Filing Date
US00193901A Expired - Lifetime US3792279A (en) 1970-11-19 1971-10-29 Ionization smoke detector

Country Status (5)

Country Link
US (1) US3792279A (enrdf_load_stackoverflow)
JP (1) JPS4940290Y1 (enrdf_load_stackoverflow)
DE (1) DE2156906B1 (enrdf_load_stackoverflow)
FR (1) FR2116395B1 (enrdf_load_stackoverflow)
GB (1) GB1300909A (enrdf_load_stackoverflow)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4223303A (en) * 1978-12-11 1980-09-16 General Electric Company Alarm devices for interconnected multi-device systems
US4401979A (en) * 1981-02-11 1983-08-30 General Signal Corporation Electrical controls for ionization smoke detector

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103680042A (zh) * 2013-11-30 2014-03-26 成都国科海博信息技术股份有限公司 火灾报警装置

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3089968A (en) * 1961-06-22 1963-05-14 Gen Precision Inc Non-linear amplifier
US3395265A (en) * 1965-07-26 1968-07-30 Teledyne Inc Temperature controlled microcircuit
US3435257A (en) * 1965-05-17 1969-03-25 Burroughs Corp Threshold biased control circuit for trailing edge triggered flip-flops
US3539831A (en) * 1967-06-15 1970-11-10 Tektronix Inc Switching circuit including plural ranks of differential circuits
US3559196A (en) * 1966-12-29 1971-01-26 Cerberus Ag Fire alarm with bistable characteristics

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3089968A (en) * 1961-06-22 1963-05-14 Gen Precision Inc Non-linear amplifier
US3435257A (en) * 1965-05-17 1969-03-25 Burroughs Corp Threshold biased control circuit for trailing edge triggered flip-flops
US3395265A (en) * 1965-07-26 1968-07-30 Teledyne Inc Temperature controlled microcircuit
US3559196A (en) * 1966-12-29 1971-01-26 Cerberus Ag Fire alarm with bistable characteristics
US3539831A (en) * 1967-06-15 1970-11-10 Tektronix Inc Switching circuit including plural ranks of differential circuits

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
The What & Why of Integrated Circuits by Stern, Radio Electronics, October 1963, pages 34, 35. *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4223303A (en) * 1978-12-11 1980-09-16 General Electric Company Alarm devices for interconnected multi-device systems
US4401979A (en) * 1981-02-11 1983-08-30 General Signal Corporation Electrical controls for ionization smoke detector

Also Published As

Publication number Publication date
FR2116395B1 (enrdf_load_stackoverflow) 1975-07-18
GB1300909A (en) 1972-12-29
DE2156906B1 (de) 1972-05-25
JPS4940290Y1 (enrdf_load_stackoverflow) 1974-11-05
FR2116395A1 (enrdf_load_stackoverflow) 1972-07-13

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