US3718919A - Ionization smoke detector - Google Patents

Ionization smoke detector Download PDF

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Publication number
US3718919A
US3718919A US00020353A US3718919DA US3718919A US 3718919 A US3718919 A US 3718919A US 00020353 A US00020353 A US 00020353A US 3718919D A US3718919D A US 3718919DA US 3718919 A US3718919 A US 3718919A
Authority
US
United States
Prior art keywords
drain
source
field effect
ionization
transistor
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
US00020353A
Other languages
English (en)
Inventor
K Sasaki
A Kobayashi
N Takahashi
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
Original Assignee
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
Application granted granted Critical
Publication of US3718919A publication Critical patent/US3718919A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • 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

  • a smoke detector utilizing a closed ionization chamber and .anopen ionization chamber each of which includes a pair of electrodes and a radio-active source are connected in series, a FET having the gateelectrode connected to the junctionof the ionization chambers, and a current limiting circuit interconnected with the source-drain path of the FET which circuit maintains the gate leakage current of the FET as low as possible during periods of operation.
  • the drain electrode 16 of the FET is connected directly to the conduct-or 6 while the source electrode 18 is connected through resistors 20 and 22 and a zener diode 24 to the conductor 8.
  • the junction 26 of resistors 20 and 22 is connected through a zener diode 28 to the gate electrode 32 of a silicon controlled rectifier (SCR) 30.
  • the gate electrode 32 of the SCR 30 is also connected through a resistor 34 to the conductor 8.
  • the anode 36 and the cathode 38 of the SCR are connected respectively to the conductors 6 and 8.
  • the drain current of the FET 12 is limited so that it cannot exceed Idl.
  • the drain current is limited, and accordingly it cannot adversely affect the gate leakage current. Since under normal conditions the ionization chamber 4 is free of smoke during the operating period, a constant ionization current will flow through chamber 4 as well as through chamber 2 so that thevoltage at junction 10 is stabilized. Under the foregoing conditions the drain current of the FET 12 will, at least, equal the leakage current of the zener diode 24'so that its value will be maintained slightly below Idl.
  • This voltage is applied to the gate of FET l2 and initiates the flow of drain current.
  • a triggering signal will be applied to the gate electrode 32 of the SCR 50 and drive it into conduction. This shortcircuits the conductors 6 and 8 of the power supply, and thus causes a large signal to be transmitted to the power supply.
  • the drain-source voltage Vds of the FET 12 is relatively low at this time, it will not affect the operation of the transistor 40 and the zener diode 50.

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  • Chemical & Material Sciences (AREA)
  • Analytical Chemistry (AREA)
  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fire-Detection Mechanisms (AREA)
  • Other Investigation Or Analysis Of Materials By Electrical Means (AREA)
US00020353A 1969-06-16 1970-03-17 Ionization smoke detector Expired - Lifetime US3718919A (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP4688769 1969-06-16
JP4688669 1969-06-16

Publications (1)

Publication Number Publication Date
US3718919A true US3718919A (en) 1973-02-27

Family

ID=26387034

Family Applications (1)

Application Number Title Priority Date Filing Date
US00020353A Expired - Lifetime US3718919A (en) 1969-06-16 1970-03-17 Ionization smoke detector

Country Status (9)

Country Link
US (1) US3718919A (de)
AT (1) AT301398B (de)
DE (1) DE2029752B2 (de)
ES (1) ES378081A1 (de)
FR (1) FR2054574B1 (de)
GB (1) GB1254839A (de)
IL (1) IL34107A (de)
NL (1) NL150595B (de)
SE (1) SE348576B (de)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2319168A1 (fr) * 1975-07-25 1977-02-18 Cerberus Ag Detecteur de fumee a ionisation
US4020415A (en) * 1974-12-30 1977-04-26 Unitec, Inc. Combustion product indicator
US4083037A (en) * 1975-12-08 1978-04-04 Patent Development & Management Company Detection circuit
USRE30117E (en) * 1975-07-25 1979-10-16 Cerberus Ag Ionization-type fire or smoke sensing system

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2130445C3 (de) * 1971-06-19 1981-06-04 Telefonbau Und Normalzeit Gmbh, 6000 Frankfurt Schaltungsanordnung für zur Meldung und Signalisierung dienende Linienstromkreise

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4020415A (en) * 1974-12-30 1977-04-26 Unitec, Inc. Combustion product indicator
FR2319168A1 (fr) * 1975-07-25 1977-02-18 Cerberus Ag Detecteur de fumee a ionisation
US4037106A (en) * 1975-07-25 1977-07-19 Cerberus Ag Ionization-type fire or smoke sensing system
USRE30117E (en) * 1975-07-25 1979-10-16 Cerberus Ag Ionization-type fire or smoke sensing system
US4083037A (en) * 1975-12-08 1978-04-04 Patent Development & Management Company Detection circuit

Also Published As

Publication number Publication date
NL7004720A (de) 1970-12-18
IL34107A0 (en) 1970-05-21
DE2029752B2 (de) 1971-12-02
NL150595B (nl) 1976-08-16
GB1254839A (en) 1971-11-24
FR2054574A1 (de) 1971-04-23
AT301398B (de) 1972-09-11
DE2029752A1 (de) 1971-01-07
FR2054574B1 (de) 1973-03-16
ES378081A1 (es) 1972-12-01
IL34107A (en) 1972-09-28
SE348576B (de) 1972-09-04

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