CA1319654C - Powder discharge apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

An apparatus for the discharge of powder by a fluidic propellant is suitable for use as a fire extinguisher, the apparatus including a container wherein powder and propellant is pressurized prior to use of the apparatus. Discharge of the powder and the propellant from the. container is accomplished by means of a diaphragm in a wall of the container, there being a gas generator contained within a well of the container for providing an overpressure which, in combination with the pressure to which the propellant has been charged, fractures the diaphragm, Thereupon, the propellant and the powder exits the container in a homogeneous stream The overpressure is less than approximately 30 per cent, preferably 20 per cent of the pressure to which the propellant and the powder are subjected during a charging of the container with the powder and the propellant. The charge pressure is in the range of 400 - 600 p.s.i. so as to be many times greater than the pressure of an environment external to the container.
A battery operated circuit may be connected between a fire sensor and the gas generator for activation of the generator in a modular self-contained form of fire extinguisher.

Description

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PCWDER DISCHARGE APPARATt;'S
"'''.'''' ' '"'' "' I ' Thi,s invention relat~es to apparatu3 for the rapid ' : homogeneous discharge of fine powder for use in the 'exti'nguishing of fire,s as well as other situations 'requiring the rapid dispersion of fine powder. ~.ore particularl~y, the invention relates to powder discha,rge apparatus wherein the powder is contained .under '.. ' pressure in a chamber or bottle and mixed with a 'compressed 'propellant fluid such as an inert gas wherein the'powder and the propellant fluid can be dicchargéd.rapidly upon a fracturing o a diaphragm of lS the chamber.
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The di~char'ge of' powdered material is employed in a v ~ wlde v.ariety of 6ituations ranging ~'rom the extingui6hlng of' fires to the dlspersement o . 20 agricultural material, ,such as insecticides, on farms.
! ~In the CaEf,e of a hand-held fire extlnguisher charged with a powdered ire suppre~6ant, the powder ls ejected ;,in'a ~teady 6tream under pre~sure by a gaseous prQpellant. However, there are situation,s, in which all of the .p'owder i8 to ~,e discharged almost ';' "inE~,tintaneous~,ly, for example within a few .. , miillisecondE,, such a ,C,ituation ari,C~ing in the extingu,i~hlng of ire6 in an aircraft, , ,,, ,, ',, .
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, . ;, :'c,-:. , , A:problem'arises in the extinguishing of fires in an ,", ."; ,,.. , alrcraf.t because of th,e need for a sudden discharge of ~,"-',' the powdered.fire-repellant material. Typically, fire-,.. . fightin,g~ equipment installed on aircraft must operate .,,.. 5 automat~cally in re~ponse to an explosive fire in order ', to.,be effective. The sensor, as i~ well known, operates , '' via an ëiectrical circuit to fire a detonator or squib ;,' to expl,~si.vely eject powder from a container thereof . . ,. ,.through:d;ut a region of the aircraft protected by the ~" , ,, 10 fi,re-fi.ghting equipment, ., , ., -.
, ,.''~ , The pow~çred fire-suppressant material operates most , " effectiv.ely when the material is dispersed as a fine y,,',." powder throughout the region affected'by the fire, ;,', , , 15 Howeverj ln the prior art, the explosive force of the ' , squib',tends to compact the powder with the undesireable r.esult,,of P'orming clumps of the material which hinder , the ef,fectiveness of the powder in extinguishing a ,,',' fir,e. .'.'.
., 20 ., ;; . A furt'her consideration in the use of the foregoing , fire-extinguishing equipment is the constructlon of the '' equipme,nt as self-contained modules. In the past, a ' , , proble~'has arisen in that the electronic circuitry ,~' ' ' 25 employe'd in automatic activatlon of the flre-'"~'. , extinguishing equipment on board aircraft has employed ,' , electr,icil power supplied by the aircraft~ such power , , belng applied typically at 28 volt~. The u~e of the ,,' aircraft power has necessitated the installation.of ,, 30 el'ectri,cal cabling with the consequent lnconvenlence of , ,,' ;'" . '';

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incorporating all such wiring within instruction manuals.employed in t~e manufacture and servicing of ' the air.. ~raft. Such cabling i5 disadvantageous in combat ~ituations w~erein shrapnel produced by an explos~on might pos~ibly sever the cabling resulting in '. ' a disabling of the fir'e-extinguishing equipment.
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, : . SUMMARY OF THE INVENTION
. 10 ,'' ' The foregoing problem i8 overcome and other advantages : . are provlded by apparatu~ for the discharge o~ powder, particularly ~or use in a fire-fighting'application, ' wherein, in a¢cordance with the invention, a powder and ; 15 a pressurlzed propellant fluid are mixed together and ' ' held unae~ pre~sure within a container ~uch a a . cylindrical or spherical bottle. One end of the bottle 1~ provided w~th a diaphragm which is scored in a : ' pattern' of line6 upon which the diaphragm fractures in the presence of over-pressure within the contalner '. Advantige is taken of the fact that in the case of . powdered.material, there is a relatlvely large amount '~' '' of space between particles of the powder, whlch space ;'' is avA~libié'for ~toring of pressurlzed propellant '' ' . ' 25 fluid, .particularly a propellant gas. By way of ' example"ln the use of a fire-fighting material such as ',' ' aluminu'm oxide, the density of the powdered aluminum "; oxids lj in'the range of approxlmately 1/6 to 1~8 of '"' the density'of the solid compacted form of aluminum ' 30 oxide, . Therefore, in a bottle of aluminum-oxide , .: ,, ,.. . .
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: powder, there is app~oximately seven time~ as much volume available for the propellant than i~ occupied by ' the powder.
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The available ~pace between the particles of the powder -. i8 used to store the f~uid propellant. The theory of ' ' the invention applies primarily to a gaseous propell'ant such as nitrogen, argon, helium, etc., since a liquid propellant would have a wetting action on the powder, - 10 which would tend to generate a slurry of liquid and - powder oreating clumps. ~owever, a slurry o~ liquid and po~der may be useful if used with a gaseous ' ' propellant. The propellant is pressurized, the ; pressur~zation greatly increasing the amount of nitrogen which is held within the container. In the ' ' preferred embodiment of the invention, a gaseous propellant, such as nitrogen, is preferred because the gaseous propellant has a considerable amount of stored energy to ald ln rapid discharge. Alternatively, a gas ~uch a8 helium may also be used since helium leak , . . . . . .
detectio'n i8 reAdily Available to check for leaks in '~ the cont~lner.

A feature''of the invention which is particularly useful 25 in the fightlng of aircraft fires is provided by the p~e~urlz~tlon of the container. It i~ readily appreciA~ted that in the ca6e of a container having a dlaphr'agm which is to be fractured in response to a pres~uré d'ifferential between the internal container pressur- and the pressure of the aircraft bay, a . .
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, reduction in bay pressure might fracture the diaphragm.
This would necessitate,a strengthening of the diaphragm with a consequent need for increased detonator pressure with a resultant excessive compact$on of the powder. In prior a~t devices, the pres~ure from the squib pushes against the powder, w~ich pushes on the diaphragm to the rupture po~nt - hence the compaction difficulty.
~owever, in the case of the invention, the container is ~nitially pressurized in the range of 400 - 600 p.s.i.
~pounds per square inch). Such pressure is many times larger than the atmospheric pressure ~at sea level) of approximately 15 p.s.i. ~ence, a loss of bay pressure results in a relatively small percentage increase of the differential pressure across the diaphragm 80 that there is no danger of premature fracture of the diaphragm in the apparatus of the invention.

, In the construction of the invention, the diaphragm i8 set to ~rActure at an overpressure of 100 p s.i. Thus, in the évent that the lnitlal pressurizatlon is at 500 p,~.i., the diaphragm ls set to ~raoture at 600 p.8,i.~
t~e additional 100 p.6.i. being provided by the squib.
During ~otivation of the apparatu~, the internal pressure of the container is increased by only 20 per i25 cent, which pressure increase is sufficiently small so ,~ as to ~V~id any clumping of the powder. In addition, the squib is oriented to push directly on the diaphragm to avoid compacting the powder. This could not be done in prior art becAuse there would be nothing to propel *he powder outward i~ the squlb pushed only on the . .
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, -6-.; . ;., : , diaphra;gm. In this lnvention the 500 p.s.i. pressure ' is available to propel, the powder outward. Thereby, the apparatus of the invention is able todischarge the powder rapidly, homogeneously, and without clumping In addition, the shearing forces generated by the 500 p.s.i. pressure aids considerably in breaking up the small powder particles into a fine cloud, this being the most effective state for fire suppression. -. .
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In accor'dance with a further feature of the invention, the powder discharge apparatus i8 constructed as a self contained module including a battery as a source of ' electric'power Electrical circuitry which is suitable for a'ctivating the apparatusin an aircraft installatlon, such as the circuitry disclosed in United States Patent No. 3,931,521 of R. J. Cinzori,'is to be modiied to be operative with the relativçly low voltage'of a battery, and is to be further modified by ~ the lnclu~ion of low-noise circuitry for more reliable '' ' ~ 20 operation of the ~en~ors with the reduced electrical supply voltag'e. Thls enables the indlvidual modules of ' the apparatus to be tested and replaced as necessary '~ from time to time without the necessity for ' interconnection with the aircraft power source, and wlthout a risk of any damage to power supply cabling durlng çombat.

' In theforegoing embodiment of the lnvention, the relatlv'~ly small overpressure may result in a ~mall ' ' 30 amount o "clumping, a~ the force of the overpressure . . . . .
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attempts to drive the fire-suppressant powder out of the container through the reduced diameter region of the exit or discharge port. Additional embodiments of the invention, to be described hereinafter, enable the use of the explosive discharge of a detonator or gas generator to free the powder without the direction of the force of overpressure in the direction of the velocity of powder exiting via the exit port. These embodiments avoid clumping of powder and facilitate a lo uniform dispersion of the powder.

Other aspects of this invention are as follows:

A self-contained fire extinguisher comprising:
a container for storing fire-suppressant powder and a fluidic propellant under pressure, said container having a port for release of the fire suppressant powder;
means located at said port and outside of said container for opening said port to allow for escape of said powder and said propellant in the homogeneous 0 discharge free of a clumping o~ the powder;
radiation sensors including a heat deteator and a light detector mounted on said container;
battery operated electrical circuitry mounted on said container and reeponsive to signals of ~aid 5 radiation sensors for activating said opening means, ~aid electrical circuitry including a filter having a pas~ band set to pass spectral components of pulsations in thermal radiation for enabling said electrical circuitry to respond to the presence of a fire; and wherein eaid electrical circuitry comprises a low-noi~e, low-current, differential ampli~ier coupled to 6aid heat detector, and an operational ampli~ier connecting said differential ampli~ier to said filter, currents drawn by said di~erential ampli~ier and by l 319~
7a said operational amplifier and by said detectors being sufficiently low to permit use of a battery by said electrical circuit for a period of time in excess of one year.

A self-contained fire extinguisher comprising:
a container for storing fire-suppressant powder and a fluidic propellant under pressure, said container having a port for release of the fire suppressant powder;
lo means located at said port and outside of said container for opening said port to allow for escape of said powder and said propellant in a homogeneous discharge free of a clumping of the powder;
radiation sensors including a heat detector and a 5 light detector mounted on said container;
battery operated electrical circuitry mounted on said container and responsive to signals of said radiation sensors for activating said opening means, said electrical circuitry including a filter having a pass band set to pass spectral components of pulsations in thermal radiation for enabling said electrical circuitry to respond to the presence of a fire; and wherein said electrical circuitry comprises a battery for powering said electrical circuitry, a low-noi~e, low-current, differential amplifier coupled to said heat detector, and an operational amplifier connecting said di~erential ampllfier to said filter;
and said electrical circuitry further comprises resistive interconnections between said differential amplifier and said operational amplifier and said battery for reducing currents drawn by said differential ampli~ier and by said operational ampli~ier each to typically ten microamperes to permit use of said battery by said electrical circuit for a period of time in excess of three years.

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BRIEF DESCRIPTION OF THF DRAWING

The aforementioned aspects and other features of the invention are explained in the following description, taken in connection with the accompanying drawing wherein:

Fig. 1 shows a stylized view of a fire extinguisher constructed in accordance with the invention;

Fig. 2 is a fragmentary sectional view showing the emplacement of a detonator within a well of a bottle of the apparatus of Fig. 1;

Fig. 3 is a ~chematic diagram of a battery operated electrical circuit suitable for activation of the fire extinguisher of Fig. 1;

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: Fig. 4A shows a sty~lized sectional view of an . alternative embodiment,of the fire extinguisher wherein - a detonator is placed in an exit port of a container of fire suppressant powder;

Fig. 4B iS a sectional';view takenalong the line4s-4s in Fig, 4A showing a scored disc and detonator in the . exit port of Fig. 4A;

:: 10 Fig. 5 i8 a view, similar to that of Fig. 4A, of a . further embodiment employing a gas generator.mounted within the container and positioned for driving a cutting blade towards a cover disc in the powder exit port;
Fig, 6 i8 a view, similar to that of Fig. 4A, of yet another embodiment of the fire extingul~her wherein a knife and detonator are mounted externally of the container and facing a cover plate to fraeture the cover for opening the exit port;

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Fig, 7 illustrate~ another embodiment of the fire extingui~her employing a double disc covering of the . exit port with a ga~ generator coupled to a space between the discs;
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Fig, 8 show~ ~till another embodiment of the fire extinguisher in which a di~c-shaped cover of the exit port i8 supported by a frangible pedestal which is 30 detonated to allow exit of the powder~ .

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Fig. 9A is a further embodiment of the invention in which a swingable door secures a closure membrane against internal pressure of a container of powder;

Fig. 9B is a sectional view taken along the line 9B-9B
in Fig. 9A showing a protractor and release mechanism for allowing the door to swing open for release of the powder;

Fig. 10 shows an embodiment of the invention in which a detonator employing a shaped charge is located within the container on a closure membrane in the exit port, there being an electric wire connected to a side connector for activation of the detonator;

Fig. 11 is yet a further embodiment of the fire extinguisher wherein a detonator employs a shaped charge aimed at the external side of a closure disc of the powder container;

Fig. 12 is an embodiment, similar to that of Fig. 10 wherein a detonator 1B mounted within the end of a tube pa~sing through the container and enclosing electric wires for activation of the detonator; and Fig. 13 shows a modification of the embodiment of Fig.
12 wherein a gas generator is employed within the central tube in lieu o~ the detonator.

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DETAILED DESCRIPTION

With reference to Figs. 1 and 2, there is shown apparatus for the homogeneous discharge of powder by a fluid propellant. The apparatus is ideally suited for use as a fire extinguisher and, accordingly, will be described as such. It is to be understoood, however, that the apparatus is also suitable for providing a rapid homogeneous discharge of powder for applications other than fire fighting.

The apparatus is shown as a fire extinguisher 10 which comprises a container 12, an electro-optic sensor 14 of radiation emitted by fire, a gas generator 16, and a battery-powdered electronic circuit 18 which is re#pon#ive to the sensing of radiation by the sensor 14 for providing an electric signal suitable for activating the generator 16 to release gas under pres~ure, The generator 16 is located within a well 20 formed within a wall of the container 12, and extends inwardly to an interior region of the container 12.
Electrical connection oi the gas generator 16 to the clrcuit 18 i# made by wires 22. The gas generator 16 i8 held within the well 20 by a housing 24 of the clrcu~t 18, the housing being secured over the well 20 to #ecure the container 12 by a set of bolt~ 26. The bolts 26 have sufficient strength to overcome the force of the gas pressure of the gas generator 16, thereby to ensure that the well 20 fractures during such a pre##ure increase to direct the pressure to the ;~
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interior o~ the conta'iner 12. Alternatively, the gas generator 16 may be secured within the well 20 by means ' of a ~lug ~not shown) ~'itted by ~crew threads to the ' ' well.
' '5 ''' ''' A port 28 i5 provided w~thin the wall of the container 12 to allow for the filling of the container with powder, and to allow for the subsequent discharge of ' ' the powder and propellant from the container l2. The pow-dered material is indicated by a stylized - representa'tion of powder particles 30. Propellant fluid, typically a gas such as nitrogen which is inert '' to a combu~tion process, is mixed with the particles 30 and is in~dicated in a tylized fashion by circles.
Alternatively, a separate port ~not shown) may be provided ~or'~illing the container, which port may be clo~ed by a 'threaded plug.

' ' Inl~lally, the port 28 is open and the powder is loaded lnto the container 12 via the open port 28. The powder may be an lnert sub~tance such as aluminum-oxide, or it '' may be chémlcally active such as sodium biçarbonate or ' ~' mono-ammonlum phosphate. In order to completely fill ' the contalner with powder, the container 12 should be vibrated as the powder i8 being loaded so as to assure adequate settling of the powder and maximum filling of the contalner' 12. The container 12, preferably, is completely filled with the powder. The particles 30 havé a diameter in the range of approximately 1 - 3 microns. In the case o~ aluminum oxide, the density of . ' , .

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. the po.wder i~ approxlmately 0.5 grams pee cubic ; '-. centimeterc this being,much lower than the density of solid aluminum oxide which has a value' of approximately 3.5 - 3.'9 grams per cubic centimeter.
. 5 The interstitial spaces between the particles 30 provides .adequate spa~e for the molecules of the gaseous propellant. ' .
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'. Upon completion of the filling of the container 12 with the powder, th'e port 28 i8 sealed with a diaphragm 34 . which is welded to the periphery of the port 28.as ''' shown buy a weld bead 36. The weld ensures the ' ' integrity o~ the container 12 for maintaining propellant gas under pressure therein fo~ extended periods of time~ The diaphragm 34 is scored at score lines 38 80 that, upon a fracturing of the diaphragm .. 34, the fractures occur along the score lines 38 in a pattern of fracture which ensures that no schrapnel is -' let loose ~rom the diaphragm 34.
" 20 After ~ecuring the diaphragm 34 by the welding, the ' ' proce8s of charging the container 12 with a desired amount of pr'opellant i8 undertaken wlth the aid of a 8prlng-loaded~inlet gas valve 40 which allows the entry of propellant gas under pressure As noted above, in : the preferred embodiment of the invention, nitrogen is ' employed;as the propellant. Accordingly, thé nitrogen '. ' i8 provided.by.a tank 42, the nitrogen being pumped out of the tank'42 by a pump 44 which connects to the valve 40 by.a high-pressure conduit 46 which may have the .
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', form of, a flexible ~o~e. A quick disconnect 48 i's secured to the end of the condu~t 46 to enable ,the , condu~t 46'to be disconnected from the valve 40 upon completion o~ the char;ging process. A gas pressure gauge 50 ~s also connected to an outlet of the pump 44 at the conduit 46 fo~; monitoring the propellant pressure in the,container 12 during the charging in the , , cont~iner with the propellant. Such charging may be , - done automatically or manually, in either case the ,, 10 charging terminating upon attainment of the desired ~',,,: pressure a's measured by the gauge 50. Upon completion, , of the charging, the quick disconnect 48 is removed : , from the v~lve 40. The valve 40 functions in a well-known' fashion to close itself in response to an ",;', 15 internal spring ~not ~hown) and in response to' the ' pressure of the propellant within the container 12.
:,i'', The prope,llant pressure within the container 12, ~t the ,'',,,, conclusion of the charging process, i~ in the range o~
m~ approximitely 400 - 600 p,8.i, , 20 ', ,In the'event that the powder was loaded into,the containér 12 in an atmosphere other than that of the ,,!, propellant~ the container 12 wlll need to be evacuated , ' ' of atmospheriC air before pres~urizing. This can be ',' '25 done by connec'ting a vacuum pump in place of tank 42 ~,,,r, ' prior tQ pressurizing. By thu~ drawing a vacuum, any ,~ , , atmosphe,rlc iir that is present between powder , particle,s 30 is drawn out by the vacuum pump leavi'ng ; ' only t,he powde~ 30 in the container. Upon completion '' ~, 30 of the evacua,tion of the air, nitrogen can be pumped in ., , ,. . .
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.' The diaphragm:34 is designed to fracture at a pressure ' , of approximately 100 p.~s.i. above the charge pressure ,. . 5 of the propellant. The container 12 and ~he diaphragm . , 34 i8 fabricated, prePerably, of a metal s~ch.as :, ' stainless steel or aluminum. Thus, in the case o~ a . propellant charge pressure of 500 p.s.i" the overpressure of 100 p.s.i. plus the charge pressur.e 500 p.~.i. results in a design fracture pressure of 600 p.s.i. for the diaphragm 34. In this case,. :th,e . overpréssure oflOO p.~.i. i~ 20 per cent of the charge ." ' pressure of SOO p.8.i. ~ypically, the diaphragm shoul'd ' be designed for an overpressure of less th'an ,,, 15 approximately 30 per cent of the charge pressure.
.,', , , This ensUres that the over pressure produced by the gas , , generator 16 i~ not 80 much larger than the c~arge : . pres~ure 80 as to introduce significant compaotion of the powder with a resultant clumping of the powder.
,, 20 . '' ,, The avoidance of the clumping of the powde'r,is "', impo,rtant,.to ensure retention of the fine size of.the " ' lndlvldu~l pa~ticles of the powder. This enable~.a '' hom,ogeneousdischarge of the powder as the powder is carried out by the propellant during a dischar'ge ofithe , . fire extinguisher 10. In addition, the direction at ", , , whi¢h the gas from the gas generator 16 enters the :,' cont.aine,r'l2 from the well 20 is aimed to be dire'cted , more,~t.the diaphragm than at the powder. A~ ~h'own in ', : 30 Fig.'.l,who~e,the gas generator 16 and the diaphrag'm 34 ', , "'' ': ' ' ' ' ',' , ,. ''"' ' ' ' ',' ' ' ', ', :, ':, , ~ , . .
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In operation, upon detection of radiation of a fire by the ~ensor 14, the electric circuit 18 activates the gas generator 16 to produce a sufficient overpressure within the container 12 to fracture the diaphragm 34.
Thereupon, the propellant and the powder i~ forcefully and rapidly e~ected from the container 12 to fill a ; space containing the fire. By way of example in a typical in#tallation of the fire extinguisher 10, the ; extinguisher 10 would be located in a dry bay of an alrcraft. Thus, discharge of the powder and the propellant within the dry bay greatly impedes the progress of the fire 80 as to extinguish the fire.
io A partlcular factor in the utilization of the oxtlngui~her 10, whlch i'actor provlde~ for the ~dvantageou~ homogeneous dlscharge, 18 the pres~urizing o~ the container 12 with the propellant at a relatively ; 25 ~low rate, sufficiently slow, as compared to the actu~tion of the gas generator 16, to ensure that the molecules of the propellant gas percolate between the particles of the powder ~o as to provide a uniform mixture without compactlon of the powder. During ; 30 actuatlon of the gas generator 16j the pressure within , .
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the container 12 builds up at a far more rapid rate, then does the build up of pressure during the charging process. In particular, such rate of increase of pressure could readily compact the powder except for the S fact that the maximum overpressure is only a relatively small fraction, in the range of 20-30 per cent of the charge pressure. Thereby, essentially no compaction of the powder occurs during the detonation and the discharge. This mechanism is aided by the swirling action generated by providing an aim point o~ the gas generator to be off centered from a center of the container 12.

Fig. 3 shows components of the circuit 18 of Figs. 1 and 2, the circuit 18 being operative, in accordance with a feature of the invention, at a relatively low voltage of approximately 2 volts conveniently supplied by a battery 52 which permits modular construction of the fire extingui~her 10 without the need for electric power cables to a remote power source.

The circuitry o~ Fig. 3 is a modi~ication of that disclo6ed in the a~orementioned U.S. patent 3,931,521.
The radiation ~en60r di6closed therein compri6es a short wavelength channel and a long wavelength channel.
Accordingly, the sensor 14 (Fig. 1) is under6tood to comprise a heat detector 54, such as a thermopile or thermistor for the detection o~ the longer wavelength radiation, namely, heat, and a C

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photodetector 56 suc~ a photovoltaic diode for detection of photong,of the shorter wavelength radiation, . ~ t:
5 The circuit 18 employs component~ which draw sub~tantially less curre~nt than the circuit disclosed in th-e aforementioned patent 80 as to provide a long lifetime for the circuit without changing the battery.
Preferably, the ba~tery 52 is a lithium battery generating 2.4 volts and having a capacity of 2.3 : ampere-hours. Signals outputted by the detectors 54 and 56 are amplified and applied to input terminals of a NOR gate 58, the latter outputting a command signal via a multivibrator 60 and a driver 62 to activate the 15 gas generator 16 via the wires 22. The NOR gate 58 provides the logic function of activatlng the generator 16 when both heat and light radiation of a fire are dete¢ted, The multlvibrator 60 i8 preset to generate an ; electrical pul~e of ~ufficient duration for operating the generator 16, and the driver 62 amplifies the power o~ the pulce to a ~ufficient level for activating the generator 16.
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The oregoing amplification of the signals of the 25 dete¢tor6 54 and 56 i6 accomplished by operational amplifier~ operating on the low voltage of the battery 52 and drawing very little current 80 a~ to allow the ' battery 52 to be employed for a period of 3 - 4 years.
; ~uch ampllfier6 64 and 66, are ~hown in Flg, 3, the amplifier~ 64 and 66 ~erving to amplify the signal of , , ~31965~

the heat detector 54, and amplifier transistor 80, 82 serving to amplify the signal of the photodetector 56.
Included in NOR gate 58 is a threshold such that signals from amp~ifier 66 and transistors 82 must decrease from their respective bias points (1.2V above ground for a 2.4V battery operation) by this threshold amount before the NOR gate recognizes the input signal as a logic "O".
The amplifiers 64 and 66 are constructed preferably as operational amplifiers. A suitable amplifier for the amplifiers 64 and 66 is that manufactured by Precision Nonolithics, part No. OP-22, which amplifier draws 10 microamperes with suitable choice of input resistors 172 and 174.

It is advantageous to connect the amplifier 64 to the heat detector 54 via a preamplifier 72 having the characteristics of low noise and low current. A
suitable preamplifier is commercially available and manufactured by Intersil with part No. IT-139, which preamplifier draws 10 microamperes when biased properly via resistor 108. The preamplifier 72 comprises two transistors 74 and 76 having their emitter terminal~
connected together to form a differential amplifier configuration.

Power for the amplifiers 64 and 66, and the preamplifier 72 is coupled from the battery 52 via a filter comprising a resistor 84 and a capacitor 86, the output voltage of the filter appearing on line 88.

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. ' Power from the.battery 52 for the amplifier 80 and 82, and the NOR gate 58 is ~rovided by a filter comprising resistor:90 and capacitor 92, output voltage of the .. ~ilter appearing on lrine 94. The resistor 84 is 5 connected, in series between the battery 52 and the line 88, the capacitor 86 beilng coupled between the line 88 , and ground. Similarlyj the resistor 90 is coupled ', between a term-inal of the battery 52 and the line 94, the capac'itor 92 being connected between the line 94 , , lO and ~round. The capacitors 86 and 92 provide paths for .', signal flow between the power lines and ground, the respective ilters isolating signals of the two .,. deteGtors 54 and 56 and inhibiting the pick up of noise fro,m'eXternal sources and crosstalk between the two ''',''' 15 circui'ts.
. .
,,. The ci~cuit 18 further comprises resistors 96, 98,104, ,, 106, and 108 which are associated with the operation of ; ' , the .pre,amplif.ier 72. The resistor 106 connects a " ' 20 ter,mlnal 'of ths heat detector 54 to a base terminal o ,, , ' the tr:a,~slstor 74. The resistor 104 matches the ~,/,,, comblnatlon o,resistor 106 and detector 54 for ofset ,','' ~ nulli~g due to bias ¢urrent. Similarly, a ~unction,of , th,e r:ési'stOr5,102 and 104 connects wlth a ba~e ~, . , 25 termf,nal of'the transistor 76 to provide a eedback ,,' ' . path ~r,om th,e, transistor 76 to amplifier 64. The ; '' . ' ' resistor, 108 is connected between ground and the ',,' ,, ' ~unction'~f the two emitter terminals of the transistor ~",, 74 an,d 76,to provide or a di~erential bias control', .,,, ~ 30 The resistors 98 and 96 are connected as load resistors .' , . . . .
,. . .
, . . . . . .

"

,; , , , : ., 1 3 ~

between the line 88 and the collectors of the transistors 74 and 76, respectively. Output signals of the preamplifier 72 are provided at the collector terminals of the transistor 74 and 76, and are coupled via resistors 110 and 112 to input terminals of the amplifier 64.

A reference voltage is provided on junction 114 by a reference voltage circuit comprising a resistor 116, and a bandgap reference 118 which are serially connected between the terminal of the battery 52 and ground. A
capacitor 120 is connected in parallel with the reference 118. The reference voltage for junction 114 appears across the reference 118. The reference 118 provides a reference voltage of 1.2 volts, a suitable diode being manufactured by National Semiconductor under part No. LM185, which diode draws 10 microamperes when biased appropriately via resistor 116. The feedback path of resistor 104 connects to the reference voltage junction 114. The reference voltage junction 114 also connects to a terminal of the heat detector 54. Typical values for resistors coupled to the preamplifier 72 are as follows, the resistors 96 and 98 each having a value of 120,000 ohms, the resistors 110 and 112 each having a value of 200 Kohm, and the resistor 108 having a value of 80 Kohm.

Output signals of the amplifier 64 are obtained via two serially connected resistors 122 and 124 with the aid of a diode 126 connected between the junction 114 and the ~S
~' 21 13196~

junction of the resistors 122 and 124. The resistor 122 and the diode 126 form a negative voltage clamp on the output signal of the amplifier 64 to avoid false triggering of the generator 16 by background radiation incident upon the detector 54.

The amplifier 66 has a feedback path comprising a capacitor 128 and a resistor 130 connected in parallel therewith between the output terminal of the amplifier 66 and a negative input terminal thereof. A series combination of resistors 132 and 134, each of which has a capacitor connected in parallel therewith, namely capacitors 136 and 138 respectively, is connected between the resistor 124 and the negative input terminal of the amplifier 66. A further series connection of resistors 140 and 142 connects between the negative input terminal of the amplifier 66 and the junction 114, a ~unction o~ the resistors 140 and 142 being connected to a positive input terminal of the amplifier 66. A
capacitor 144 is connected in parallel with the resistor 142. The capacitor~ 136, 138, and 144, in combination with their corre~ponding resistors 132, 134, and 142 provide ~or a high-pass filter ~unction, while the feedback capacitor 128 in combination with the feedback re~i~tor 130 provide for a low-pass filter function.
The combination of the two filter function provides a desired bandpass characteristic to the amplifier 66 ~or identi~ylng the spectral components of pulsations in thermal radiation which identi~ie~ the presence of a ~ire.

22 13196~

The diode 56 is operated in the photoconductive mode for converting photon energy of optical radiation from the fire into electric current, which current flows through the resistor 146. Incremental changes in voltage drop across the resistor 146 are coupled via capacitor 148 to a base terminal of the transistor 80. The transistor 80 and an output NPN transistor 82 are cascaded as shown to provide the necessary amplification for the photodiode signal, which, when amplified, is coupled through resistor 182 to the other input of the NOR gate 58. The transistor~ 80 and 82 are connected to the necessary and conventional bias, feedback and current limiting resistors 162, 152, 154, 150, and 160 for bia~ing these transistors to nonconduction in the absence of an input signal from the diode 56. The resistor 146 is adjustable in order to vary the overall sensitivity of this detector 56. The gain of amplifier tran~i~tors 80 and 82 is controlled by the values of reei~tore 154 and 158. A DC supply voltage for the amplifier transistors 80, 82 is connected at terminal 94 to provide the necessary operating power for this amplifier ~tage, and a filter capacitor 156 i8 connected across reslstor 160 for the purpose of decoupling the bia~ eupply from the circuit. By appropriate choice of resi~tore 160, 150, 152, and 146, the amplifier tran~i~tor~ 80, 82 can be made to operate on less than 10 microamps from the battery 52.

Each of the amplifier~ 66 and 82 provides a negative-going voltage in response to eignals outputted by their -23- 131~6~
respective detectors 54 and 56, the joint occurrence of the two low-voltage output signals resulting on a triggering of the multivibrator 60 by the Nor gate 58. Relatively high values of voltage are outputted by the amplifier 66 and transistor 82 in the absence of signals outputted by the respective detectors 54 and 56. Using commercially available parts NOR gate 58 can be implemented using a 74HCOZ NOR gate with 74HC14 Schmitt triggers at the inputs to achieve the threshold effect and prevent oscillation for slowly changing inputs. (Two series Schmitt triggers will be needed since the 74HC14 is an inverting gate.) If more precise control of the threshold is needed, an OP-22 amplifier can be used with low voltage germanium diodes connected from resistor 182 and amplifier 66 to the negative input and a precise threshold with slight positive feedback set at the positive input. Thereby, the logic function represented by the NOR gate 58 can be accomplished with circuitry operative with the relatively low voltage of the battery 52 with minimal current drain.

I~ desired, it is also possible to connect additional circuitry (not shown) for testing the sensor 14. Such additional circuitry would include a switch for connecting an external source o~ power in lieu of the batter 52, and would also include light emitting diodes (LED's) for activating the two detectors 54 and 56 in a test mode. To prevent the output drive of driver 62 from activating the generator 16 during the test, an optical coupler such as that manufactured by 1 3 1 ~
.
' ' ' ' -24-: Honeywel'l having part No. SPX7270 can be used to clamp . the ~ignal o~ the driver 62, without interference with normal:operation of t~e circuit 18. A second such optical. coupler can be~used to couple the output drive . 5 signal to external test equipment for monitoring the result of the te~t. i, , Such~testing can al~o include a test of the pressure in the container 12 by including a pressure gauge that 10 transmits an electrical signal indicating the amount of pres~uré, Such signal can be temperature compensated by use of a resistive circuit employing a resistor having a resi tance'which varies with temperature. A suitable conhector ~not shown) can be mounted on the fire extinguisher 10 to facilitate electrical connection of the remote test equipment during the conduction of a test, It is nsted that the foregoing teachings for the ' 20 cir¢uit l8 and the te8t mode are also applicable for u~e with a fire extinguisher wherein the container holds a'fire suppressant liquid, such a~ Halon, which llquid rapidly turns to a gas upon a fracturing of the diaphràgm, .' The foregoing description of the container of the fire suppressant powder and the mechanism for di~charging the'powder is capable of producing the desired result oi jowder discharge with reduced effect of clumping, However,'some clumping may occur due to the fact that , , , .
, ", : ~ . 13196~
-., -25-.. .: . - , .
there i~ an overpr~ssure due to the explosion of the : ~ squib, ~hich overpressure acts within the powder for - forcing the powder th~ough the exit or discharge port.
- : To overcome ~his situation, further embodiments of the ; 5 invent~ on are provided wherein the discharge of powder is obtained by use o~ a detonator or gas generator : without the development of an overpressure which produces a force in the direction of the powder velocity during discharge. ~hese latter embodiments of the invention avoid the tendency to clump the powder i - during discharge o~ the powder.
.'; , Figs. 4-i3-show sectional views, partially stylized, of additional embodiments of fire extinguishers incorporating the invention, these figures relating to the containment vessel for the powdered extinguishant and conigu~ations of dev~ces for opening a discharge ; port of the containment vessel for discharge of the powder. Electrical circuitry, suitable for activation oi' the discharge apparatu~ i8 the same as that which has been disclo8ed in Fig. 3. The basic physical 8tructures of the extinguishers in the following alternative embodlments are similar to tho~e already described wlth preferènce to Fig8, 1 and 2 so that only a simplif~ed description of the embodim0nts o~ Figs 4-13 need be provlded to explain the es~ential features thereof.
' ' ' ', Fig8, 4A-4B show a fire extinguisher 200 including a vessel 202 for containing a ~ire-extinguishing powder ,' ' ' ', , , , .. .. . .
, , ,,"';'' ' ' -26- 13196~
: - , .. ..
and pressyr'ized ga~ foY expelling the powder from the , ve~sel 202. The vessel 202 i8 filled with ~he powder . -, and ga~ via a filling port 204 located in the side of ., the vessel 20i. The vess.el 202 terminates in a neck 206 : - .5 which defines an discharge port 208 which is closed off ' . ~y a disc 210 which ~,s curved in the form of a ~ spherical 'segment. The. disc 210 is scored along two '' intersecting lines 212, 214 which facilitate ; fragmentation of the disc 210 for expulsion of the powder.

A rapid, opening of the discharge port 208 for the .' extinguishing of a fire is attained with the aid of a , detonator 216 disposed within a well 218 located in a ,. 15 supporting plug 220. The plug 220 i~ located in the ~,' neck 206 between the powder and the closure disc 210.
The plug 220 may be scored on the under~ide at 222 facing the disc 210 to facilitate a fracturing of the plug 220 outwardly from the center of the vessel 202.
The detonator 216 i~ actlvated by an electrical circuit ~uch a~ that di~clo~ed in Flg~ 3, the circuit being connected to the detonator 216 at a connector 224., !' ' In opera,tion, upon appllcation of the electric signal as vi~ ,the connector 224 to the detonator 216, the detonat.or 216 explodes resulting in a fragmenting of the plug 220.. The pre~sure of the gas in the vessel 202 , i~ substantially greater than that of the outside environment, a~ wa~ disclo~ed with reference to the " ' ,30 fire extinguisher 10 of Fig~ 12, With the , s, ,:"
: .. . .
, . . :.

: ~L3196~ --27--,: :
fracturing of the plùg,220, the pressurized gas forces the ~ragment~ of the plug 220 towards the disc 210 and ,,', fracture~ the disc 210 to allow the gas and the powder to escape vla the di'æcharge port 208. vanes 226, ' 5 indicated diagrammatically, extend in a flared conf$guration from a r~m 228 of the neck 206 to assist ' ~n a uni$orm dispersion of the fire-extinguishing powder. In this embodiment of the invention, it is noted that over pressure generated by detonation of the detonator 216 is exerted upon the powder in a direction away from the direction of exit velocity of the powder 80 as to avoid clumping of the powder during di~char,ge of the powder from the extingui~her 200.

... . .
',' ' 15 Further,details of construction are the following. The vane~ 226 may be angled at a flare angle of approximately 60 degree~ from a central axis of the neck 206. The disc 210 may be clecured at the periphery thereof withln a circumferential slot 230 ~ormed between an inner section 232 and an outer section 234 of the 'neck 206. ~he two neck #eCtions 232 and 234 i" provide a pressure tight seal with the disc 210 80 that , ,' the plug 220 need not provide a pressurized seal, the plug 220 ~erving simply to support the detonator 216 in , 25 lts position relative to the powder and the disc 210.

A further embodiment of fire extinguisher 200A, shown in Fig. 5, includes components similar to that disclosed in Figs. 4A--4B. The ve~sel 202 o~ Fig, 4A
30 has been modified to provide the ves~el 202A in Fig. 5 :- ~ 13~9654 . . , ,; .
by the inclusion of a,gas generator 236. ~he generato~
' 236 ha a ~enerally cylindrical shape and is positioned :' along,a central axis of the extinguisher 200A, and includes a connector 238 protruding through the top of the vessel 202A for receipt of an activation electrical signal from an ac~vating clrcuit such as the : aforementioned circuit 18. Gas and powder are held undér pressure within the vessel 202A as disclosed in the pr,evious '~mbodiments of the invention. The vessel 202A terminate~ in a neck 206A which defines an exit port 208A ~or discharge of the ga~ and the powder. The clo~ure disc 210 is secured within a circumferential siot 230 of the neck 206A in the same fashion as wa~
disclosed in Fig. 4A for providing a pressure-tight seal for holding the gas and the powder within the ves8el 202A.

A feature in the con~truction of the embodlment of Fig 5 18 the ln¢lusion of a knife assembly 240 compri~ing , 20 ~our triangular knive8 242 arranged symmetrically about '~ the ce'ntral axis of the extinguisher 200A and forming a , ¢ommon point directed towards the center of the disc 210, In both the embodiments of Figs, 4A and 5, the concave 8urface of the disc 210 ~aces the center'of the ' , 25 vessel'2,0'2~ his facilitates rupture of ths disc 210 ",, ' '' during di~,¢harge of the powder by the pre~sure of the ':, ' ga8 and,detonator in Fig, 4A, and by the pressure of the ga~ and an advancement of the knives 242 in Fig, 5.

In FIg, 5, the ga~ generator 236 is enclosed within a ,; , , .
. " ' ' ' ,, . ~ , ., .
. . .
,, ; , . . .
...

-29- 1319~5~
cylindrical wall 244 which also includes a piston 246 which forms a part of the knife assembly 240. The piston 246 is located within an end portion of the cylindrical wall 244.
A pressure seal 248, in the form of a diaphragm is located within the cylindrical wall 244 to prevent leakage of the compressed gas within the vessel 202A past the knife assembly 240.

In operation, upon receipt of the electrical signal at the connector 238, the gas generator 236 rapidly produces gas under pressure which forces the piston 246 and the knives 242 downward to perforate the disc 210, thereby allowing the gas and powder to be discharged from the interior of the vessel 202A. The vanes 226 facilitate a uniform discharge pattern of the powder. The uniform dispersion of the powder is aided by placing some of the vanes 226 within a central portion of the discharge port 208A, in addition to the mounting of individual ones of the vanes 226 on the rim 228 of the neck 206A. Support of vanes 226 within the central portion of the discharge port 208A can be accomplished in both the embodiments of Fig. 4A and Fig. 5 with the aid of rods (not shown) extending transversely across the necks 206, 206A, these rods having been deleted in Figs. 4a and 5 ~or clarity.

In the embodiment of Fig. 5, the cylindrlcal wall 244 has su~icient strength to prevent rupture of the gas generator 236 into the vessel 202A, thereby to avoid the generation of a hydrostatic force which would act ~' . 13196~
.
.

in the dire,ction of the velocity of the escaping . powder. Therefore, the construction of Fig. 5 wherein the..gas generator 2;36 is contained within the . cylindrical wall 244f prevents the clumping of the . : 5 powder.during di~charge from the ve~sel 202A.
l I
,. Fig. 6' shows a fire extinguisher 200B which shares , features with the extinguisher shown in Figs. 4A and 5, ,, and also ~n.cludes a neck 206s extending from a vessel ',. 10 202B.to ~orm an exit port 208B for the discharge of gas ' and 'powder contained within the vessel 202B. The ,;' vessel 202B ha~ the same general shape as the ves.sel : : 202.of Fig. 4A. The neck 206B is provided with a end wall 250 which extend~ perpendicularly to a central : ' 15 ax1s of the,extinguisher 200B and includes a set of , windows 252 po~itioned uniformly about a cylindrical " wa'11 of the néck 206s for directing a discharge of the" ~ extin.guishant powder in a clrcular pattern about the , longitud.inal ixis of the extinguisher 200B. Also ' , 20 included in'the extingui6her 200~ is a knife assembly 254, the,knie.assembly 254 extending from a protractor ,'' ' 256 upst'an,ding from the end wall 250.
., . . . .
"
,, ~he knife assembly 254 has a four-knife configuration,' 25 as does'the knife assembly 240 of Fig. 5, and points ,',' towards the, concave surface of the di~c 210. Thç ~isc ~ . 210.i~ secured in pressure-tight fashion to the neck '~; ' 206.B i'n.. the same fashion a~ was disclosed with i,; , ' ' re'~er'e,n¢e, to the necks 206A of Fig. 5. An electric '" ' 30 signal'.provided from an actlvation circuit, such a~ the .

;. '. ' . "' . " '. " '' ' . ''. ' ,' ' :

... .

~:;

` ` 13196 : -31-.: . . ..
aforementio'ned'circuit',l8, is coupled via wires 258 for activating' the protr,actor 256 to detonate ~ith a conse~uent expulsion of the ~nife assembly 254 against the,..di'sc 210. Thereby, the knife assembly 254 fractures the disc 210 with the con~equent release of the ga~,and powder fro~ the vessel 202B. It is readily appr,e.ciate~ that none of the escaping gas produced by deto,nation of the protractor 256 develops a fo~ce which would-,intr:oduce compaction to the extinguishant powder upo~ dl~charge of the powder from the vessel 202B.

In Fig.,.7,,,a.fire extinguisher 200C i~ formed of a ve~el 202C extending lnto a neck 206C which form6 a port, 208C f,or discharge of gas and powder contained within the vessel 202C, In a fashion similar to that dis:closed in Fig, 6, the neck 206C includes a set of win.~ows,25,2 which provide for a circular discharge of powder,abou.t a central axis of the extinguisher 200C.
Thé nec,k 206,C is provided with a end wall 250A which forces the powder to di~charge sideways through the window~'252, and also serves a# a ne~t for receipt of a dl~c,,2.10A upon di~charge of thè powder. The disc 210A
di~fer~,from,the con8truction oi the disc 210 in that a cl~,dular score line (not shown) is formed within the ''7~,'' ~ 25 disc 210A a,t a line of contact wlth a ~lot 230 in the neck 2'06C.

~he éx,,tinguisher 200C includes a further di~c 260 secured,to"a base of the neck 206C between'the disc 210A'and the powder. A vent 262 is formed as a fine 0~ :
.. . . .
, :, , ! ~ , "

, , ' ' ' 13196~
. - -32-.. . ,: . . .
bore within a lip at,the base of the neck 206C, the bore o.f'.the vent 262 being sufficiently small, '. typicai,ly less than ,one milllmeter in diameter, to . . allow th,e p.ressure oftgas contained within the vessel :'' 5 200C to,~,be,.equalized on both sides o the di~c 260 , during fil~ing and pressurization of the ves~el 202C.
;,''., . ' ~he .d~'ameter of the bore o~ the vent 262 is ,'.. :. ~ufficiently. small to provide a time constant of .at least a' few seconds for the pressure equalization. The ' ' 10 disc 210A copnects to the neck 206C with,an air-tight .'. seal as has,been descr~bed with reference to the disc .~ 210 of.Fig. 4A.
.
;, :, . .
:";' The n,ec,k 206C, supports a housing 264 which extends . 15 'radially outward from the base of the neck 206C and cQntaln'~ a,.gas generator 266 separated from the space :~' . bet.w,een the discs 260 and 210A by a seal 268.
," po~,tion'o the housing 264 i8 formed as a conduit 270 ~o~',gulding,gas from the generator 266 ,to the space ,., 20 betw,een,t~e dlscs 260 and 210A during d~scharge of the ,; , .' exti,ngulshant powder from the veesel 202C. ~he seal 268~1É located wlthin the conduit~ 270, and serves to ', retain thé static pres~ure within the vessel 202C by : pr,éuen,t~ng escape of gas lnto the reglon of the ", 25 gene,rat,or'266. The ~eal 268 1~ structured in the form of a diaphr;ahgm or a dlsc similar to that of the d~sc ,210, but on a smaller ~cale, The gas generator 266 is éxc,ltéd.by an electrical signal provided by an ' excitatlon circuit, such as the aformentloned circuit 18, whiqh is to be connected by a connector 272 to the .. .

. .
. .. . .
.:, ~ , . .. ..
: , , . . . .
, . .

-`'`'''. . ' ': _33_ " 13196~
,.~. . . : .
.:: s ' genera,tor: 266. ''.
.:, . .
, , In operation, upon exci~ation oi~ the generator 266, gas s. is prQdu~ed'qnder pre~sure to rupture the seal 268, the ' ~ gas f.lowing,via the conduit 270 into the space between : . the two~ cs 210A anld,260. The pressurized gas from , ,.' the gen.erator 266 ~.ractures the disc 210A at the nter~ace w,ith the edge of the slot 230, the compressed ' ' ga~,thereafter driving the disc 210A down to the end " 10 wall,250A. The end wall 250A has a concave surace ,. . facing the disc 21 OA if or receiving the disc 21OA upon . the activation oi~ the generator 266.
.: . . . " ', .
~hé di~c 26,0 has a relatively lightweight construction, .. , , 15 as compared:to the disc 210A, so as to readily fracture ,, u~o~ a loss of equalization oiE the hydrostatic pressure " on bot,h s~ides of the disc 260. Such loss of ; . equalization occurs upon the displacement of the disc , 210A to"ward'the end wall 250A. By way of example, a ,; 20 typica'l value of pressure in the gas produced by the ' ,', generator'266 is 1000 psi . Here too, it is ob~erved that ~he.domed construction of the inner llghtwelght disc Z60,.in cooperation with the internal pressure of , the vessel 202C, tends to resist the pressure of the 25 gas gen;erator 266 80 as to facilitate the detachment oiE
the outer disc 210A iErom the base of the neck 206C.
.
The for.,ce exerted by the gas Erom the generator 266 is ' ' produced outside oiE the vessel 202C, and, thereby, does ,~" 30 not,pr:ess against the powder in the direction of the , , "
. .
, S,. . .
.
., . ,:
,,;,' . ' , ' :' .

~ .

131965~

discharge velocity, thereby avoiding a possible clumping of the powder during discharge.

Fig. 8 discloses an embodiment of fire extinguisher 200D
having a vessel 202D extending into a neck 206D forming a discharge port 208D. The neck 206D is provided with windows 252 and an end wall 250B which directs discharging powder in a circular pattern about a central axis of the extinguisher 202D. The discharge port 208D
iB closed off by a foil membrane 274 held by a support 276 to provide a pressure-tight seal which preventæ
egress of the gas and powder contained within the vessel 202D. A mating surface between the outer peripheral edge o~ the support 276 and the inner surface of a base portion of the neck 206D is flared outward at 278 to facilitate a displacement of the support 276 towards the end wall 250B upon discharge of powder from the vessel 202D.

The ~upport 276 i~ held in position against the force of the pressurlzed gas within the vessel 202D by a frangible post 280 which rests upon the end wall 250B.
The post 280 is hollow, and enclo~es a detonating compound 282 which is electrically activated by a signal ~rom an activating circuit, such as the aforementioned clrcuit 18. Upon application of the electric signal to the detonating compound 280, the compound detonates with a destruction of the post 280 with a resultant release of the support 276. The support 276 is then forced away from the ves~el 202D

"~ '-' ,' ' ' '~35~ ' 13196~
.; . . .. ;
towar;ds the ènd wal~; 250B by the pressure o~ the gas ;,-, ; within t~e ve~sel 202b. The gas pres~ure also tears ,, the ;membrane 274 im~ediately upon loss of the ,:, su~por~ing force of t,he support 276. ~hereupon,the ',:, 5 powder ~ischarges through the port 208D and exits in a " circul~ar pattern thro,ugh the windows 252. Here too, - the construc-tlon of the fire extinguisher 200D prevents ~,- , the force of detonation from clumping powder during ',, discharge'from the vessel 202D.
,;;; 10 : In F'ig. 9A a fire extinguisher 200E is provided with a ;:' dischargé port 208E which i8 closed by a trap door ~84 ' which Bwi~gB about a pivot 286, and sec~red by a tab ; , , 288, sho~n'in Fig. 9B, the tab 288 being held by a pin, ', 15 290. Both the pivot 286 and the pin 290 are secured " wit~in a supporting ring 292 mounted to a neck 294 of a ,'", ' vessel.202,E whicb contalns extinguishant powder and ', ~ressuilæed",ga~ of the extinguisher 200E. The ring,292 ' also supports a protractor 296 which connects with the ' 20 pin 290;, and upon electrical activation of the " protra¢tor'296, expels the pin 290 from its position 90 ~ a~ to relea~e the pin 290 allowing the door 284 to ," swing,opén, A foll, membrane 298 i8 supported by a plug 300 so as to ' , provld,e a pr,es~ure-tight seal for the contents of the ",,',", vessel '202E. The plug 300 is slideably mounted within , the rlng 292, and is held in position by the door 284.
Upon r,elease of the door by the ~iring o~ the :: 30 protractor 296, the plug 300 is expelled from the ' i , .
, '~
", " .
... .

. '' ..

'' ,' '',, " .",' -36'- 1 3 1 9 6 ~ 4 . ~ ... . .. .. .
: ' vesse.l'~02'E by the prce of the contained pressurized ,'',. gas, the force of the gas also tearing the membrane 298 ,.". . ' to open .the dischar,ge port 208E. Here too, the ;' ;,, contents' o~.,the vesse~ 202E are mechanically isolated ,s , 5 from an explosion of the protractor 296 so as to ':, . prevent ~;ny clumping of the extinguishant powder during .. a,d,is.charge of the powder. During the discharge, the ',..... powder e.xits in a direction parallel to the central ,;.' . axis.of the extinguisher 2~0E.
, ' 10 , . .Fig.. lO ~h.ows a ~ire extinguisher 200F WhiCh is ". similar to'that disclosed in Fig. 4A , except that the ,.' disc 210! in Fig. lO, i~ fractured by use of a shaped-charge ,detonator 302 supported by a frangible support ~,~, ' 15 304, su,ch as a pla~tic screen, The detonator 302 is t ' ' "' ' el,ec,trically activated by an external activation ~', , circui,t,'such as the circuit 18, with t,he aativating ,,'' el,ectric s,i'~nal being applied via connector 306 mounted ~ ' to ~he exterior of a vessel 202F, which vessels i'', ' ' 20 ¢ontalns ext'ingui8hant powder and gas under pressure or the ex,ti'nguishant 200F. Connection between the , cc,nnec'~r 306 and the detonator 302 is made by means o~
":: wire~ 308,which pa8s within the ve~sel 202F. Hot gases , eml,tt~d by thè detonator 302, upon detonatlon, burn "~,, , 25 th.ro~gh the dlsc 210, thereby de8troying the disc 210 '. and aiiowing the contents of the vessel 202F to be discha~ged. Because of the shaped charge, the blast of ',', . ' the'd,etonator 302 is exerted primarily towards the disc ' ' , '210,'and aw,iy from the center of the ves8el 202F, ~he ; , 30 blast i~ ¢ompleted before dlscharge of the contents of ~ ' ' !
''"1 ' ~ , ~' , ~ . . .
~', ' ', , , "
,;', , ', ' ' , . . . .
, .................. ...
.

13196~

the vessel 202F so as to prevent clumping of the powder during discharge. The force of the discharge breaks the support 304 and expels the shattered support 304 during the discharge, so that the support 304 does not interfere with the discharge of the powder.

In Fig. 11, a fire extinguisher 200G is a modification of the fire extinguisher 200F of Fig. 10 in that the detonator 302 is mounted, in Fig. 11, exteriorly to the disc 210, and is excited electrically via wires 308 as is the case in Fig. 10. The shaped charge of the detonator 302 is directed towards the disc 210 for destroying the disc upon detonation of the detonator 302. This permits the contents of a vessel 202G of the extinguisher 200G to be discharged. Here too, the force of the detonation is directed in a direction other than the direction of powder velocity during the discharge, BO aB to avoid clumping of the powder.

In Fig. 12 and 13, fire extingui~hers 200H and 200J are variations of the extinguishers ~hown respectively in Flg~. 10 and 11. The embodiment~ of Figs. 12 and 13 each contain a cylindrical chamber 310, 312, respectively, containing an electrically activatable explosive device for fracturing a disc 210 in lieu of the detonators 302 of Figs. 10 and 11. The chambers 310 and 312 are mounted along central axes of their respective ve~sels 202H and 202J which contain extinguiehant powder and pressurized gas.

:.~ 13196~
, , --38--: . In Fig. i2, the bot~om end o~ the chamber 310 holds a .:, . cap 314.which, in turn, contains a detonator 316. A
seal 31~ is .located o~ ,the exterior surface of the cap 31i and'is secured to the walls of the chamber 310 to .,., 5 preven.t egress,'of pressurized gas from the vessel 202H
; . into the,'c.hamber 310. Electrical activation of the . :,.' detonator 316 is accomplished via signals applied via a :',., connector 320 located on top of the vessel 202H and .' . elect'ric wi~e's 322 passing within the chamber 310 and ,. ' 10 connecting the connector 320 to the detonator 316.
.
,. . .. . . .
,''. In F~g.. 13, the chamber 312 is closed off at its lower ,'"', . end by,'a foil seal 324 which prevents egress o~
:" " ' pressurize,d;gas from the vessel 202J into the chamber ; ,. 15 312. :.The chamber 312 contains gas generating compounds ;,,', ,' ' 326., which ar,e. activated by an electrical igniter 328 in ",, respon~e to signals coupled thereto by wires 322 and ,, . connec~or .3io.
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',,,,, 20 In bo;th the e~bodlment~ of Flgs, 12 and 13, explosive ,,,' , forc,é's gellerated withln the chambers 310 and 312, ;', ' re~péc~,lvely, are directed toward# the di~c 210 to , " frac'tu.re the disc and allow dlscharge of the contents ,~, , of the' ves~q"ls 202H and 202J, respectlvely. In the "' 25 case df ,the ga's generation within the chamber 312 of , F.ig,, 13, the explo~ion occurs at a slower rate than, the ' ' explo~lon ass,ociated with the detonation ln the chamber ,' 310 o~"Fig. 12. As a result, the embodiment of Fig, 13 ;.,, ' i,8 less ?lkely to produce shrapnel upon the destruction " ,. 30 of the.d~;~c 210.
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Both the embodiments of Figs. 12 and 13 provide conveniences in manufacture. upon completion of the physical structure of the extinguisher 200H or 200J, the extinguisher is filled with the extinguishant powder, then the vessel 202H or 202J is sealed with the disc 210. The vanes may then be assembled with the bottom portion of the neck, this being followed by pressurization of the vessel to approximately 450 psi.
The manufacture is then completed by inserting either the detonator 316 in the chamber of 310, or the gas-generation compounds 326 in the chamber 312. It is noted that these chambers are constructed in the form of a well for receipt of the explosive materials at any time of convenience during the manufacturing procedure.

With respect to the various embodiments of the invention, it is noted that the embodiment of Figs. 1 and 2 does provide a significant advantage in resistance to clumplng of extinguishant powder than was available in aimilarly constructed fire extingulshers of the prior art. A~ has been noted above, this advantage is provided by the etoring of the powder in a pressurized gas environment within the pressure containment vessel.
The static pressure within the vessel is sufficient such that only a relatively small ~ractional increase of pressure is required to open the discharge port. As noted above, such fractional increase in the pressure may introduce some clumping of ; :

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. the powder,"which c~lumping i~ substantially less than ,,., is found,in similarly,constructed fire extinguishers of ,, the prior art. ' .
' ., , 5 The further,embodimehts of Figs. 4-13 produce still further advantages ov'er the embodiment of Figs. 1-2 as may be.appreciated frd.~ the following discussion.
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, , In th.e case of a fire extinguisher constructed in a fashion whe'rein the combustion gas o~ a detonator or a ,, gas ge.nerator mingles with the powder and compressed , ga~ st,ored 'in the containment vessel, the powder ',,,' . ex~ingui,shan.t cools the combu~tion ga~. This ,.' ne.ces~lta.te;s a considerable increase o~ propellant ,.,:" 15 charge';,t,o a,¢hie~e the required discharge pressure. In '' i . a typ~cil"situation, by way of example, 6 grams of , " black''powd.er,'to 80 grams of extlnguishant are employed ,,;,~ , to pro,vide,360 psi burst pressure. This results in an ;~', increase of'.burning time euch that several milliseconds ",; , 20 may ,be, required before the burning produces the , requi~ite discharge pres~ure. Any additional use of ,' ' 'proFellant would make the weight of the propellant to ,, , be a an appreciable percentage of the extlnguishant . .
,,, weight.. , " ' 25 . "
'':. ' ' ~In'thé; embodiments of Figs. 4-13, the, physical con~iguration of the containment vessel and the appa,ratus which opens the ves~el, such as a detonator ,, ' 6haped,'charge, a knife assembly, a trap door as~embly, , ,.., , 30 or dual di,s¢ as~embly, provides for adequate separation , .

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. . i ""'' ' ' ,''' -41- 13196~4 ' , of thë combustion ga,s and the fire extinguishant materials of the containment vessel to avoid the foregoing:cooling phe~o,menon of the extinguishant , powder.'Also, as has been noted hereinabove, the emplacement of the site of the detonation in the , ,;, vicinity of the discharge port, rather than within the containment vessel, as well as the complete separation ~', ' of the detonation from the containment vessel, prevents ' ; the relatively small clumpin~ associated with the ,;: 10 discharge overpressure in the embodiment of Figs. 1-2.
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'-' , Other advantages are as follows. The extinguisher deslgn avoids excessive weight. The powder is ejected ' ~rom a relatively ~mall diameter which permits a secure '~ ', 15 closure to protect personnel and equipment from accid,ental,damage during a fall.
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, Tbe'design'of the fire extinguisher provide~ for a ''"'' rapid and,even dispersion o~ the extinguishant because ~,' 20 the gis-p'owder mixture has fluid flow properties.
Initlally, extinguishant is pro~ected with maximum ,, veloclty,and '18 carried rapidly to the limlts o~ a compartment ('such as a compartment on board an ' aircra~tl wh,lch is protected by the extinguisher. ~he,;','' 25 gas pre~ure d,écays progressively as the extinguisher '" emptie~,'"this ensuring that an even disper~ion is ach~eved., The small orifice at the discharge port ,' permits, the use'of relatively small sized deflection '' , vané~ ,to indu'ce a predetermined di~charge pattern optimized for a particular configuration of compartment ,'',' ' ' '.' '', .
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~3196~4 which is to be protected. Discharge of the extinguishant materials is initiated within only a fraction of a millisecond.

Also, the fire extinguisher may be mounted in any desired attitude. The disc~arge time of the fire extinguisher is established by the configuration of the discharge port relative to the overall volume of the containment vessel. A narrowing of the discharge port increases the discharge time, while a widening of the discharge port reduces the discharge time. The mass flow rate is very high as compared to extinguishers of the prior art.

Various gases may be employed as the compressed gas within the containment vessel. An inert gas is fire suppressant. Helium is a convenient gas to use because it i~ readily detected by a mass spectrometer to assess hermetic sealing o~ the extinguisher.

The configuration of the extinguisher permit~ the cover o~ the discharge port, such as the domed disc or foil membrane supported by a riding plug, to be secured adequately to the neck of the vessel for retaining gas pressure over an extended period of time, such as ten years. For long retention time, the wall of the containment vessel and the construction of the discharge port should be sufficiently rigid to resist any tendency to creep under the influence of the long term pressure.

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: 43 . It is to be understoo~ that the above described : embodiment of the invent,ion is illustrative only, and that modifications thereof may occur to those skilled in the art. Accordingly, thlæ invention i8 not to be - . . 5 regarded as li:mited to the embodiment disclosed herein, but is to be limited oniy as defined by the appended claims.
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Claims (6)

1. A self-contained fire extinguisher comprising:
a container for storing fire-suppressant powder and a fluidic propellant under pressure, said container having a port for release of the fire suppressant powder;
means located at said port and outside of said container for opening said port to allow for escape of said powder and said propellant in the homogeneous discharge free of a clumping of the powder;
radiation sensors including a heat detector and a light detector mounted on said container;
battery operated electrical circuitry mounted on said container and responsive to signals of said radiation sensors for activating said opening means, said electrical circuitry including a filter having a pass band set to pass spectral components of pulsations in thermal radiation for enabling said electrical circuitry to respond to the presence of a fire; and wherein said electrical circuitry comprises a low-noise, low-current, differential amplifier coupled to said heat detector, and an operational amplifier connecting said differential amplifier to said filter, currents drawn by said differential amplifier and by said operational amplifier and by said detectors being sufficiently low to permit use of a battery by said electrical circuit for a period of time in excess of one year.

2. A fire extinguisher according to Claim 1 further comprising a battery for powering the electrical circuitry, and wherein said operational amplifier has.
two input terminals, and said differential amplifier comprises a first transistor having a first collector terminal, a first base terminal and a first emitter terminal;
a second transistor having a second collector terminal, a second base terminal and a second emitter terminal, the emitter terminals of said transistors being connected to each other at an emitter junction;
an emitter resistor connecting said emitter junction to a first terminal of said battery, said first base terminal being connected to said heat detector;
a first load resistor connecting said first collector terminal to a second terminal of said battery, a second load resistor connecting said second collector terminal to the second terminal of said battery, a first coupling resistor connecting said first collector terminal to a first of the input terminals of said operational amplifier, a second coupling resistor connecting said second collector terminal to a second of the input terminals of said operational amplifier; and wherein said electrical circuitry includes a feedback path interconnecting an output terminal of said operational amplifier with said second base terminal.

3. A fire extinguisher according to Claim 2 wherein said battery provides a voltage having a typical value of 2.4 volts between said battery terminals;
each of said load resistors has a typical resistance of 120,000 ohms, each of said coupling resistors has a typical resistance of 200,000 ohms, and said emitter resistor has a typical resistance of 80,000 ohms; and said first and said second transistors together draw typically ten microamperes from said battery.

4. A fire extinguisher according to Claim 3 wherein said heat detector is a thermopile, the fire extinguisher further comprising a first base resistor interconnecting said first base terminal with said thermopile; and wherein said feedback path comprises a second base resistor interconnecting said second base terminal with said output terminal of said operational amplifier, and a third resistor interconnecting said second base terminal with said first battery terminal, said operational amplifier drawing typically ten microamperes from said battery.

5. A self-contained fire extinguisher comprising:
a container for storing fire-suppressant powder and a fluidic propellant under pressure, said container having a port for release of the fire suppressant powder;
means located at said port and outside of said container for opening said port to allow for escape of said powder and said propellant in a homogeneous discharge free of a clumping of the powder;
radiation sensors including a heat detector and a light detector mounted on said container;
battery operated electrical circuitry mounted on said container and responsive to signals of said radiation sensors for activating said opening means, said electrical circuitry including a filter having a pass band set to pass spectral components of pulsations in thermal radiation for enabling said electrical circuitry to respond to the presence of a fire; and wherein said electrical circuitry comprises a battery for powering said electrical circuitry, a low-noise, low-current, differential amplifier coupled to said heat detector, and an operational amplifier connecting said differential amplifier to said filter;
and said electrical circuitry further comprises resistive interconnections between said differential amplifier and said operational amplifier and said battery for reducing currents drawn by said differential amplifier and by said operational amplifier each to typically ten microamperes to permit use of said battery by said electrical circuit for a period of time in excess of three years.

6. A fire extinguisher according to Claim 1 wherein said operational amplifier has two input terminals and said differential amplifier comprises a first transistor having a first collector terminal, a first base terminal and a first emitter terminal;
a second transistor having a second collector terminal, a second base terminal and a second emitter terminal, the emitter terminals of said transistors being connected to each other at an emitter junction;
an emitter resistor connecting said emitter function to a first terminal of said battery, said first base terminal being connected to said heat detector;
a first load resistor connecting said first collector terminal to a second terminal of said battery, a second load resistor connecting said second collector terminal to the second terminal of said battery, a first coupling resistor connecting said first collector terminal to a first of the input terminals of said operational amplifier, a second coupling resistor connecting said second collector terminal to a second of the input terminals of said operational amplifier; and wherein said electrical circuitry includes a first base resistor interconnecting said first base terminal with said heat detector; and a feedback path interconnecting an output terminal of said operational amplifier with said second base terminal, said feedback path comprising a second base resistor interconnecting said second base terminal with said output terminal of said operational amplifier, and a third resistor interconnecting said second base terminal with said first battery terminal.