US2632885A - Fire detection apparatus - Google Patents

Fire detection apparatus Download PDF

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Publication number
US2632885A
US2632885A US103427A US10342749A US2632885A US 2632885 A US2632885 A US 2632885A US 103427 A US103427 A US 103427A US 10342749 A US10342749 A US 10342749A US 2632885 A US2632885 A US 2632885A
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United States
Prior art keywords
current
wires
fire
bridge
coils
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Expired - Lifetime
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US103427A
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English (en)
Inventor
Sidney F Barclay
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Grinnell Corp
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Grinnell Corp
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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
    • G08B17/06—Electric actuation of the alarm, e.g. using a thermally-operated switch

Definitions

  • This invention relates to an improved fire detection apparatus, more particularly'for the op-' eration of so called deluge systems for fire-ex-- tinguishingand has for its object to provide a simple and reliable apparatus which will detect an outbreak of'fire rapidly and may readily be I extended to cover a large area without complica tion.
  • a further objector" the invention is to provide afiredetection apparatus having a temperature detecting element of a simple and robust nature without electrical contacts or moving parts of any kind, which obviates the necessity for mounting complicated heat sensitive devices at the roofs of buildings where they are often in accessible and: may be required in large numbers.
  • the arrangement according to the invention comprises two electrical conductors, one being covered. with heat-insulating material and. the other bare, or: coated with a heat absorbent material, which. are mounted in a position in which. they are equally exposed to heat from an out break of tire, the conductors being connected to an electrical power source and to means for detecting. a. predetermined increase in the resistanceof. the bare conductor relatively to the covered conductor and for operating an extinguisher system or: an alarm in accordance with such relative increase in resistance.
  • the conductors conveniently take the form of flexible stranded wires and are made of the same material: having the same-temperature coefficient of electrical resistancewhich preferably has a high value.
  • the wires preferably have the-same cross. section. and length;
  • Figure. l is a circuit diagram of one form of the invention, indicating the manner in which it is: installed in. a building;
  • Figure 2. shows diagrammatically the arrangementirr the roof of a building.
  • FIGs 3" and 4 are similar diagrams for another form of the invention.
  • Figure 5 is a diagrammatic showing of the encults in a polarized magnetic amplifier.
  • the ends of the wires 0., b are connected in two arms of a Wheatstone bridgatwo equal fixed resistances c, d, form the ratio arms of" the bridge.
  • A. direct-current electric power supply is connected across the bridge and a small variable resistance a is included in thebridge to allow for accurate zero setting.
  • a relay 9 will operate a circuitto a solenoid which trips the main valve of a deluge system.
  • the Type MAE 3' magnetic amplifier put out by Electro Methods, Ltd, of London, England,
  • a polarized magnetic amplifier is one designed to operate close by one end of the limited range, referred to above, so that when the D. C. controlcurrent flows in one direction it has substantially no effect on the A. C. output fier l6, conductor l2", a rectifier l8 and return conductor 28.
  • the coils 12a and..l2b are so..
  • a full wave rectifier 26 is connected between conductors l2 and and provides a rectified A. C. current (in effect, a D. C. current) which flows in a third circuit loop comprising a con-' ductor 28, coils 28a and 2812, also wrapped around These coilscore [4, and a return conductor 38. 28a and 281) are so wrapped about the core that the'magnetic lines of force produced by the current flow in each coil are added to one another.
  • the purpose of rectifier 26 is to produce the proper degree of core saturation so that whenno D. C. control current is flowing from the Wheatstone bridge through coils 22a and 22b, the magnetic amplifier is operating close by one end of the limited range in which the change in, A. C. output current is substantially proportional;
  • rectifier 26 provides a core saturation bias.
  • This'rectified A. C. current is in the nature of a feed back and will amplify the effect of the D. C. control current if coils 32a and 32b are so wrapped that the lines of magnetic flux,
  • Rectifier I8 is connected in series with the rectifier l6- and in turn is also connected by wires 35 and 38 with the relay g.
  • the rectified A. C. current which is filtered by a condenser 40 connected across the wires 36 and 38, operatesthe relay g.
  • a resistance in is connected in series with the bare wire b and is normally short-circuited by a switch 2'.
  • the switch 1 When the switch 1 is opened the bridge becomes unbalanced to the same extent as when the bare wire is heated under a fire condition, and the equipment can therefore easily be tested by opening the switch.
  • the bridge circuit may be supplied with alternating instead of direct current, in which case a rectifier for the out-of-balance current will be required.
  • the rectifier is so connected that it yields. current to the amplifier only when the out-of-balance current results from the bare wire being at a higher temperature than the covered wire.
  • a convenient value for the current 1 in the bridge circuit is 3 amperes, each of the wires 11, b (and m, n when used) taking 1.5
  • the wires can be and'preferably are of considerable cross section in order to realise mechanical strength and reliability.
  • the detectors consist of three strands of copper wire each 0.029 inch diameter.
  • hot gases tend to accumulate along the centre line of the the wires may be run along ,each'bay, or along some of the bays, according to size, with close spacing of the wires.
  • a small room In the case of a small room,
  • the wires may be necessary to arrange the wires in the form of a very open grid under the ceiling, in order to obtain the desirable length. Short wires would be effective, electrically, but would need to be of fine diameter and so lack robustness.
  • an installation in accordance with our invention may be given any desired rate of response to" fire by varying the value of the current flowing in the roof wires and/or by varying the amplification of the signal current takenfrom the bridge.
  • tive response is usually desired so that the installationwill operate when the outbreak of fire has .caused the temperature of the bare wire to bev increased by only a few degrees Fahrenheit, as compared with the covered wire. It is therefore obvious that if doors or windows of a heated building are opened, an inrush of cold air could quickly cool the bare wire to such an extent as A highly sensi-' to cause the generation of a signal current from the bridge of sufiicient amplitude to bring the installation into operation, in the absence of any provision to the contrary.
  • the installation operates only when the bare wire is heated and not when it is cooled, relatively to the covered wire.
  • the means we adopt to detect and utilise the change in resistance is polarised so that the relay contacts close only when the bare wire is heated relatively to the covered wire and not when it is cooled.
  • we employ a sensitive polarised difierential relay with the opposing coils connected in series with the bare and covered wires.
  • the constant consumption of electricity which the device requires is small and has the important advantage that there is a gentle warming of the roof wires and associated equipment which tends to prevent condensation and corrosion and to preserve the electrical insulation in good condition.
  • the invention is applicable in all cases where it is desirable for the rate of response to an outbreak of fire to be in proportion to the rate of increase of temperature and not to the absolute temperature attained.
  • the fire detection apparatus and deluge may be installed in sections in order to avoid unnecessary water discharge, in the event of a small outbreak of fire.
  • An advantage of the fire detection apparatus according to this invention is that the wires are dispersed over a large area and will respond to a general through small rise in temperature whereas known devices will respond only to a concentration of heat. Nevertheless, the fire-detection apparatus described herein responds equally rapidly when only a short length of the wires is affected by a concentrated outbreak of fire.
  • a fire detection apparatus comprising two wires forming a pair of parallel loops extending throughout an area to be protected in positions in which the said loops are equally exposed to heat resulting from the outbreak of fire, one of said loops being capable of being heated more rapidly than the other and thereby changing the relative resistance of the two loops and the relative flow of current through them; a Wheatstone bridge having one of its arms interconnected with and embracing one of said loops and having another of its arms interconnected with and embracing the other of said loops; said bridge being connected to an electrical power source and to means for detecting a predetermined decrease in the current fiow in one loop; the last said means including a diiferential polarized magnetic amplifier from which a predetermined output energizes a relay to close a circuit to a solenoid and 'thereby efiect'the giving of an alarm; the said predetermined output being produced by a change in the impedance of said amplifier occasioned by the change in current fiow in the said loop which is more rapidly heated.

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  • Business, Economics & Management (AREA)
  • Emergency Management (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Fire-Extinguishing By Fire Departments, And Fire-Extinguishing Equipment And Control Thereof (AREA)
  • Fire-Detection Mechanisms (AREA)
US103427A 1948-07-21 1949-07-07 Fire detection apparatus Expired - Lifetime US2632885A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB281300X 1948-07-21

Publications (1)

Publication Number Publication Date
US2632885A true US2632885A (en) 1953-03-24

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ID=10270726

Family Applications (1)

Application Number Title Priority Date Filing Date
US103427A Expired - Lifetime US2632885A (en) 1948-07-21 1949-07-07 Fire detection apparatus

Country Status (5)

Country Link
US (1) US2632885A (enrdf_load_stackoverflow)
BE (1) BE490155A (enrdf_load_stackoverflow)
CH (1) CH281300A (enrdf_load_stackoverflow)
FR (1) FR989541A (enrdf_load_stackoverflow)
GB (1) GB644542A (enrdf_load_stackoverflow)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2824278A (en) * 1954-10-01 1958-02-18 Honeywell Regulator Co Liquid level sensing apparatus
US2861159A (en) * 1953-08-31 1958-11-18 Du Pont Resistance probe for level control
US2896057A (en) * 1956-10-29 1959-07-21 Statham Instrument Inc Temperature control device
US2904995A (en) * 1953-12-10 1959-09-22 Illinois Testing Laboratories Dew-point detecting device
US2945218A (en) * 1955-05-19 1960-07-12 Bailey Meter Co Monitoring system including a magnetic amplifier
US3023398A (en) * 1958-04-09 1962-02-27 Charles L Siegert Infra-red radiation monitor
US3109165A (en) * 1958-09-05 1963-10-29 Specialties Dev Corp Intruder detecting system
US3643245A (en) * 1970-03-11 1972-02-15 Kidde & Co Walter Discrete heat-detecting system using a thermistor detecting element
US4325145A (en) * 1978-04-06 1982-04-13 Corbett Marshall J Thermal detection system

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR611455A (enrdf_load_stackoverflow) * 1926-09-29
GB250589A (en) * 1925-04-07 1926-12-30 Thermosonus Soc Alarm contrivances for fire alarm and other purposes
FR632050A (fr) * 1926-07-06 1927-12-30 Système de signalisation à distance
US2236891A (en) * 1937-07-17 1941-04-01 Gamewell Co Fire alarm system

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR611455A (enrdf_load_stackoverflow) * 1926-09-29
GB250589A (en) * 1925-04-07 1926-12-30 Thermosonus Soc Alarm contrivances for fire alarm and other purposes
FR632050A (fr) * 1926-07-06 1927-12-30 Système de signalisation à distance
US2236891A (en) * 1937-07-17 1941-04-01 Gamewell Co Fire alarm system

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2861159A (en) * 1953-08-31 1958-11-18 Du Pont Resistance probe for level control
US2904995A (en) * 1953-12-10 1959-09-22 Illinois Testing Laboratories Dew-point detecting device
US2824278A (en) * 1954-10-01 1958-02-18 Honeywell Regulator Co Liquid level sensing apparatus
US2945218A (en) * 1955-05-19 1960-07-12 Bailey Meter Co Monitoring system including a magnetic amplifier
US2896057A (en) * 1956-10-29 1959-07-21 Statham Instrument Inc Temperature control device
US3023398A (en) * 1958-04-09 1962-02-27 Charles L Siegert Infra-red radiation monitor
US3109165A (en) * 1958-09-05 1963-10-29 Specialties Dev Corp Intruder detecting system
US3643245A (en) * 1970-03-11 1972-02-15 Kidde & Co Walter Discrete heat-detecting system using a thermistor detecting element
US4325145A (en) * 1978-04-06 1982-04-13 Corbett Marshall J Thermal detection system

Also Published As

Publication number Publication date
BE490155A (enrdf_load_stackoverflow)
FR989541A (fr) 1951-09-10
GB644542A (en) 1950-10-11
CH281300A (fr) 1952-02-29

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