US3590321A - Fire alarm device - Google Patents

Fire alarm device Download PDF

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Publication number
US3590321A
US3590321A US749166A US3590321DA US3590321A US 3590321 A US3590321 A US 3590321A US 749166 A US749166 A US 749166A US 3590321D A US3590321D A US 3590321DA US 3590321 A US3590321 A US 3590321A
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United States
Prior art keywords
cover means
field
effect transistor
gate electrode
short circuit
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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
Application number
US749166A
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English (en)
Inventor
Andreas Scheidweiler
Max Kuhn
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Cerberus AG
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Cerberus AG
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Publication date
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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

Definitions

  • FIRE ALARM DEVICE I BACKGROUND or THE INVENTION This invention relates to fire alarm devices of the type containing at least one detector element sensitive to a phenomenon resulting from combustion, a field-effect transistor for amplifying an electrical signal produced by the detector element, connections for an electrical circuit for giving an alarm and a cover which protects the gate electrode of the field-effect transistor and the circuit components connected with it again external contact.
  • Another object of this invention is to provide a switch means operable on removal of a cover over the field-effect transistor to short circuit the gate electrode to another electrode of the transistor.
  • Yet a further object of the invention is the use of either a resiliently biased switch member which is movable by a guide element on displacement of the cover or a reed switch and a permanent magnet with a ferromagnetic member interposable therebetween on proper positioning of the cover to prevent flux from the magnet from actuating the switch or wherein the member of ferromagnetic material forms on additional per manent magnet which neutralizes the field of the first permanent magnet.
  • a fire alarm device including a detector element responsive to a phenomenon resulting from combustion to generate an electrical signal, a field-effect transistor arranged to amplify the signal and to supply an amplified signal to an alarm circuit and cover means normally preventing external contact with the to short circuit said gate electrode to another electrode of said transistor and operable in response to the correct placement of said cover means to remove the short circuit.
  • FIG. 1 shows a cross section through a fire alarm device incorporating one embodiment of the invention
  • FIG. 2a shows in cross section a modification of that part of the device of FIG. 1 lying to the left of the line A-A;
  • FIG. 2b shows a plan view of the modified embodiment shown in FIG. 2a, partly in cross section taken along line 8-8;
  • FIG. 3 shows in cross section another modification or the apparatus of FIG. 1;
  • FIG. 4 shows a circuit diagram of a fire alarm device incorporating the inventive concepts.
  • the fire alarm devices to which the illustrations relate are known as ionization fire alarms in which the detector element sensitive to a phenomenon resulting from a fire consists of an ionization chamber including a radioactive substance.
  • the measurement ionization chamber 10 is connected in series with a reference ionization chamber 11 and connected by way of supply leads or conductors l and 3 to a central station (not shown).
  • the common connecting point or junction 50 (FIG.
  • the gate electrode 14 of a field-effect transistor 12 which amplifies the alterations of voltage appearing at this point of the circuit and delivers at its source electrode 51 a signal which is applied by way of an alarm terminal 2 to a known alarm circuit (not shown).
  • the source electrode 51 of transistor 12 is connected by way of a resistor 9 to supply lead 3.
  • a short-circuiting switch 15 which is open during normal operation, that is with the cover of the alarm device closed.
  • the short-circuiting switch may equally well be arranged between the gate electrode and the source electrode, as shown in broken lines at 15'.
  • FIG. 1 shows the greatly simplified construction of an ionization fire alarm device in accordance with FIG. 4.
  • an electrode 17 common to a measuring ionization chamber 10 and a reference ionization chamber 11.
  • Two radioactive sources 18 and 19 ionize the air molecules present in the chambers 10 and II respectively.
  • the reference ionization chamber 11 is provided with an electrically conductive housing 20 which rests upon an insulating base 30 and is effectively airtight; the external air has practically free entry into the measuring chamber 10, which is bounded by a housing 21 provided with perforations 22.
  • the housing 20 of the reference ionization chamber 11 also forms the second electrode of that chamber, and the housing 21 of the measuring ionization chamber 10 forms the second electrode thereof.
  • the housing 21 of the measuring ionization chamber 10 is push or screw mounted on to a baseplate 23 and may be removed for cleaning or repair purposes; the casing or housing of the measuring chamber 10 is connected by way of a contact member 29 with supply lead 3 and is usually grounded.
  • the measuring chamber housing 21 also serves as a cover which protects the individual parts of the alarm device, and especially those elements which are in connection with the gate electrode 14 of the field-effect transistor from direct contact.
  • a switch 15 is provided, as already explained with reference to FIG. 4 which, by a device described below in more detail, is automatically closed upon removal of the measuring chamber housing 21, thus short circuiting the gate elec trode 14 of the field-effect transistor 12 to one of the other electrodes, as shown for example, to the drain electrode 13.
  • the switch 15 consists of a movable spring contact which, if no external 'force is applied, is resiliently biased into engagement with a fixed contact 24.
  • Fixedly connected to the measuringchamber housing 21 is a disc 25 of insulating material with a protruding cylindrical flange 26.
  • the pin 28 is urged upward (relative 'to the showing in the drawing) and gate electrode 14 of the field-effect transistor 12 is connected to the drain electrode 13.
  • FIG. 2a which represents a modification of that part of the fire alarm device of FIG. 1 which lies to the left of line A-A shows another arrangement of switch 15 and its actuating means.
  • FlG. 2b is a partial sectional plan view of the device of FIG. 2a, taken along the line B-B.
  • Switch 15 which in its rest position short circuits the gate and drain electrodes of the field-effect transistor, employs here a reed switch 31 having its contacts enclosed in a protective gas atmosphere. Since, in contradistinction to the spring contact of FIG. 1, the contacts of reed switch 31 are normally open, a permanent magnet 32 mounted on a base 33 is provided, which closes the contacts of reed switch 31 when the housing 21 of the measuring chamber is removed.
  • a member of ferromagnetic material which prevents theflux from the permanent magnet from actuating the switch.
  • a ring 34 which in this case consists of a high permeability ferromagnetic material and which, when the measuring chamber housing 21 is in position for operation, is positioned between the permanent magnet 32 and the reed switch 31 to screen the flux of the magnet from the switch, thus preventing'the magnet from actuating the reed switch.
  • One contact of reed switch 31 is connected by way of a lead 35 with electrode 17 and the other by way of a lead 36 with the housing 20 of the reference chamber.
  • a cover 37 is provided to protect the components of the alarm device against the entry of external air, dust, etc.
  • FIG. 3 shows a modification of the alarm device of FIG. 20, using a reed switch, in which ring 32 fitted to disc 25 now consists of a further permanent magnet, which when the measuring-chamber housing is correctly positioned for operation is positioned so as to neutralize the first permanent magnet and to prevent actuation of the reed switch 31 so that the contacts of reed switch 31 remain open.
  • the remaining references correspond with those of FIG. 1.
  • the invention has been particularly described only with reference to ionization fire alarm devices, but it will readily be appreciated that the inclusion of a short circuiting switch and a device actuated by the cover which determines the setting of the switch can advantageously be utilized in any kind of fire alarm device in which a field-effect transistor is employed as an amplifying device.
  • the detector element 10 might be replaced by a temperature-dependent resistor or a photocell, and the reference element 11 by a resistor or by some other suitable bridging element, as will be apparentto those skilled in the art.
  • a fire alarm device including a detector element responsive to a phenomenon resulting from combustion to generate an electrical signal, a field-effect transistor having gate, source and drain electrodes, arranged to amplify the signal and to supply an amplified signal to an alarm circuit, and cover means normally preventing external contact with the gate electrode of said field-effect transistor, the improve ment which comprises switch means operable in response to the displacement of said cover means to short circuit said gate electrode to another electrode of said transistor, to thereby protect said transistor against damage from static charges, and said switch means being operable in response to the correct placement of said cover means to remove the short circuit.
  • said switch means includes a movable contact resiliently biased into engagement with a fixed contact, and actuating means operated on correct positioning of said cover means to force said movable contact away from said fixed contact.
  • said actuating means comprises a pin freely movable in a guide, a member secured to said cover means which engages said pin when said cover means to correctly positioned, said pin engaging said movable switch contact to force it away from said fixed contact.
  • a fire alarm device including a detector element responsive to a phenomenon resulting from combustion to generate an electrical signal, a field-effect transistor having -gate, source and drain electrodes, arranged to amplify the signal and to supply an amplified signal to an alarm circuit, and cover means normally preventing external contact with the gate electrode of said field-effect transistor, the improvement which comprises switch means operable in response to the displacement of said cover means to short circuit said gate electrode to another electrode of said transistor and operable in response to the correct placement of said cover means to remove the short circuit, said switch means including a reed switch having resiliently biased contact members, a permanent magnet whose magnetic field extends between said permanent magnet and said reed switch in order to urge together said contact members against their resilient bias when the cover means is removed, and a member of ferromagnetic material which prevents the flux from the permanent magnet from actuating said reed switch when the cover means is correctly positioned.
  • a fire alarm device including a detector element responsive to a phenomenon resulting from combustion to generate an electrical signal, a field-effect transistor having gate, source and drain electrodes, arranged to amplify the signal and to supply an amplified signal to an alarm circuit, and cover means normally preventing external contact with the gate electrode of said field-effect transistor, the improvement which comprises switch means operable in response to the displacement of said cover means to short circuit said gate electrode to another electrode of said transistor and operable in response to the correct placement of said cover means to remove the short circuit, said switch means being connected between the gate and the source electrodes of said field-effect transistor.
  • a fire alarm device including a detector element responsive to a phenomenon resulting from combustion to generate an electrical signal, a field-effect transistor having gate, source and drain electrodes, arranged to amplify the signal and to supply an amplified signal to an alarm circuit, and cover means normally preventing external contact with the gate electrode of said field-effect transistor, the improvement which comprises switch means operable in response to the displacement of said cover means to short circuit said gate electrode to another electrode of said transistor and operable in response to the correct placement of said cover means to remove the short circuit, said switch means being connected between the gate and drain electrodes of the field-effect transistor.
  • a fire alarm device including a detector element responsive to a phenomenon resulting from combustion to generate an electrical signal, a field-effect transistor having gate, source and drain electrodes, arranged to amplify the signal and to supply an amplified signal to analarm circuit,

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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)
US749166A 1967-08-09 1968-07-31 Fire alarm device Expired - Lifetime US3590321A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CH1120067A CH460594A (de) 1967-08-09 1967-08-09 Feuermelder mit einem gegen Berührung geschützten Feldeffekttransistor

Publications (1)

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US3590321A true US3590321A (en) 1971-06-29

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US749166A Expired - Lifetime US3590321A (en) 1967-08-09 1968-07-31 Fire alarm device

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US (1) US3590321A (enrdf_load_html_response)
CH (1) CH460594A (enrdf_load_html_response)
DE (2) DE6603864U (enrdf_load_html_response)
FR (1) FR1575250A (enrdf_load_html_response)
GB (1) GB1192298A (enrdf_load_html_response)
NL (1) NL160101C (enrdf_load_html_response)
SE (1) SE333696B (enrdf_load_html_response)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3762515A (en) * 1972-06-07 1973-10-02 Ltv Aerospace Corp Apparatus for shielding portions of a vehicle
US3913083A (en) * 1973-12-11 1975-10-14 George O Baker Control system for aircraft refueling facilities
US4114194A (en) * 1976-04-22 1978-09-12 Clairol, Inc. Ultrasonic cleaner
WO2012101443A1 (en) * 2011-01-26 2012-08-02 Thorn Security Limited Fire detector unit

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH491449A (de) * 1969-05-19 1970-05-31 Cerberus Ag Rauchdetektoranordnung mit mindestens einer Rauchmesskammer
DE102016200913A1 (de) 2016-01-22 2017-07-27 Hekatron Vertriebs Gmbh Vorrichtung zur Leitungsüberwachung von Gefahrenmeldern und Feststellvorrichtungen
DE102016200914A1 (de) 2016-01-22 2017-07-27 Hekatron Vertriebs Gmbh Vorrichtung zur Leitungsüberwachung an einer Feststelleinrichtung von Brandschutztüren mit Rauchschaltern
CN113570805B (zh) * 2021-09-23 2021-11-23 江苏优思智能科技有限公司 一种智能建筑灾情报警监控装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2756299A (en) * 1953-08-10 1956-07-24 Motorola Inc Radio cover switch
US3222473A (en) * 1961-03-06 1965-12-07 Jose H Delhase Combined switch and closure means
US3413497A (en) * 1966-07-13 1968-11-26 Hewlett Packard Co Insulated-gate field effect transistor with electrostatic protection means

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CH355380A (de) * 1957-10-30 1961-06-30 Cerberus Gmbh Einrichtung zur Feststellung von Änderungen in der Zusammensetzung eines Gases

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2756299A (en) * 1953-08-10 1956-07-24 Motorola Inc Radio cover switch
US3222473A (en) * 1961-03-06 1965-12-07 Jose H Delhase Combined switch and closure means
US3413497A (en) * 1966-07-13 1968-11-26 Hewlett Packard Co Insulated-gate field effect transistor with electrostatic protection means

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3762515A (en) * 1972-06-07 1973-10-02 Ltv Aerospace Corp Apparatus for shielding portions of a vehicle
US3913083A (en) * 1973-12-11 1975-10-14 George O Baker Control system for aircraft refueling facilities
US4114194A (en) * 1976-04-22 1978-09-12 Clairol, Inc. Ultrasonic cleaner
WO2012101443A1 (en) * 2011-01-26 2012-08-02 Thorn Security Limited Fire detector unit
GB2487560B (en) * 2011-01-26 2013-09-04 Thorn Security Fire detector unit

Also Published As

Publication number Publication date
GB1192298A (en) 1970-05-20
NL160101C (nl) 1979-09-17
FR1575250A (enrdf_load_html_response) 1969-07-18
NL6811153A (enrdf_load_html_response) 1969-02-11
NL160101B (nl) 1979-04-17
DE1766669B1 (de) 1971-10-21
DE6603864U (de) 1969-11-13
SE333696B (enrdf_load_html_response) 1971-03-22
CH460594A (de) 1968-07-31

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