US2524100A

US2524100A - Flame responsive fire alarm system

Info

Publication number: US2524100A
Application number: US326650A
Authority: US
Inventors: Dauvillier Alexandre; Ponte Maurice
Original assignee: CSF Compagnie Generale de Telegraphie sans Fil SA
Current assignee: Thales SA
Priority date: 1939-04-03
Filing date: 1940-03-29
Publication date: 1950-10-03
Anticipated expiration: 1967-10-03

Description

Oct 3 1950 "I A. DAUVILLIER Err AL 2,524,100

FLAME RESPONSIVE FIRE ALARu sYs'rEu Filed March 2S, 1940 MVNIORS ALEXANDRE DAQVMJER MFWNCE PDHT av: U

RTTORHEYS Patented Oct. 3, 1950 FLAME nasronslva ma ALARM SYSTEM Alexandre Dauyillier and Maurice Ponte, Paris, France, assigncrs, by mesue assignments, to Compagnie Generale de Telegraphie Sans Fil,

Paris, France Application March 29, 1940, Serial No. 326.650 In France April 3, 1939 Sections 3 and 14, Public Law 690, August 8,1946 Patent expires April 3, 1959 2 Claims. (CL 177-355) This invention is for improvements in or relating to ire alarm systems and detectors of radio active materials.

Fires are generally detected by devices which respond to a rise of temperature. Systems including such devices of necessity only detect the fire after some damage, has been caused which may be considera-ble and, in order to reducevthe damage to a minimum, it is necessary to employ a comparatively large number of such alarm devices over a given area.

The use of re detection by the light emitted by the conagration has been restricted in view of the fact that it is necessary that such systems .should not be unintentionally operated for cxample by daylight, artificial iight and the like.

The present invention obviates such a pombility and also the necessity of producing very sensitive detector systems actuated by the light' emitted by an incandescent ilre, without it being set in operation by normal sources of light, or by daylight.

The -present invention consists in employing the property inherentin unprotected flames of emitting to some distance (for example 2,200 to 3,000 A. U. or more) considerable quantities of ultra-violet radiations of which the ordinary sources of illumination are devoid owing to the ultra-violet rays being absorbed by the glass of their globes and in the case of daylight to the solar ultra-violet being absorbed by the terlight can be iiltered by a Wood glass thereby eliminating the radiations contained in solar light or the undesirable radiations proper to the installation to be protected.

The tube contains a mixture of rare gas and oxygen at a pressure in the vicinity of one tenth of an atmosphere; it also contains an anode for the passage of the discharges.

There could also be employed a device incorporating a illling of hydrogen at a suitable pressure; in this case use should be made of a suitable filter to allow the passage of radiations of short wave length.

The invention will be more particularly described with reference to th accompanying drawings, in which:

Figure 1 illustrates one embodiment of the .present invention comprising a cylindrical tube,

Figure 2 illustrates .a modiied form of tube to that illustrated in Figure 1, and

Figure 3 illustrates a circuit arrangement in which either of the tubes illustrated in Figures 1 or 2 may be employed.

Referring to Figure 1 of the drawings, a cylindrical tube `comprises a central median part transparent to ultra-violet light. The tube contains a cathode cylinder 2 a part of Vwhich is constituted by a grid 3. A ilne anodic axial wire 4 is stretched by springs 5 mounted in holder restriai atmosphere.` The detector system comprising the present invention will be only sensitive to the ultra-violet emanations. Finally the system is designed and constructed in such manner that the ultra-violet reception by the system is expressed by a system of discharges of comparatively high frequency .which are employed by any known system to operate a desired relay.

The detector according to the present invention is of a type employing the properties of the discharges in comparatively high gaseous pressures. It is composed essentially of a meter tube, the major portion of which may be ofglass for convenience of manufacture but which is provided with a window of quartz; it contains'a tubes 6. The electrodes are for example made of platinumv carefully puried of any traces of hydrogen and the photo-electric portion of which is at a distance suilicient for the system to be sensitive to the ultra-violet rays only at a distance from the unprotected names. Nickel y is also suitable. A system of this nature gives photo-cathode constituted of an only slightly electro-positive element (ferrous metal such asat the reception of each ultra-violet photon (or .of greater frequency) a very short discharge if the source of supply is suitable. In darkness o1' in daylight the system is only traversed by a small number of discharges per second caused for example by the cosmic rays or the radioactivity of its surroundings. As soon-as it is subjected to the light coming from .an unprotected llame, the number of discharges per second increases considerably, for example up to 10,000 or 20,000, and it is this phenomenon which is employed to detect the llame. 'Ihe sensitivevness of the system is considerably higher than that of an ordinary photo-electric cell and may be employed directly with the arrangement illustrated in Figure 3, without any ampllc'ation': Voltage values are given on the drawing.

The same advantages may be obtained with a tube o1' the shape illustrated in Figure 2. In this construction the quartz transparent body I is of a cylindrical shape with a hemispherical end. The axial wire 2 serves to deposit on its internal surface, by thermal or cathodic evaporation, a`

semi-transparent photo-sensitive cathodic layer.

-The electric contact with this deposit is obtained by a metallic wire attached to the glass 3 by means of a silvered or aquadag ring I.. The wire 2 serves as an anode; the tube is filled with rare gas and oxygen at the same pressure as that given for the tube illustrated in Figure 1.

. Figure 3 represents the employment of the embodiment illustrated in Figure 2 with a circuit arrangement employing a pentode.

The anode 4 of a pentode i is connected to the anode 2 of the detector I and also to a source of high tension (300 to 1000 volts) through a high resistance Il. for example four megohms. A control grid t of the pentode 5 is connected to the cathode l of the detector l and also to a source of polarisation through a very high resistance Il, for example megohms. A screen 1 is raised to a normal positive potential such as 100 volts. When the detector l is at rest, the pentode is only traversed by a very -feeble current. When the detector receives a photon (for example a cosmic ray) a. discharge takes place between the anode I carried to a high potential and the cathode; the anode potential drops whilst at the same time the potential of the control grid rises in consequence of the development of a positive potential in the grid resistance; the pentode is traversed by a current impulse corresponding to the amplification of the pentode and the detector is extinguished;

each photon thus gives a very brief impulse and a' listening device located ,at 8 will indicate a shock. Thus the described system, placed in the shade or in daylight or in a normalartiilcial light such as that of an incandescent lamp, will indicate a series of irregular shocks, for example 40 per second. But if the detector is subjected to the light of a bare flame the number of shocks becomes very great (for example, several thousands); the telephone receiver will give a buzzing noise due to this frequency and a micro-ammeter located at l will register an increase of mean current which may be from a few micro-amperes to thirty or ilfty. A relay i2 placed at the same point may be actuated by this current and set any desired system in operation. An idea of the sensitiveness of the apparatus may be given by stating that the phenomena above described are caused by the flame of a match placed a few metres distant.

If necessary, amplification by any usual sys- I- tem such as thyratron relays could be used.

The detectors above described can be used wherever it is necessary to detect bare'flames, tire in residences, automatic surveillance and localisation of forest fires, use in mining galleries and the like.

On the other hand the apparatus only requires supplies of litle importance, the whole thus forms a very compactblock which is easy to shift. As the detector is equally sensitive to photons of very great energy such as Y and other rays, the apparatus described, mounted in this way will be usefully employed in prospecting for radio-active materials either in galleries or pits or even in the sea by making a water-tight apparatus.

The apparatus may also be employed in hospi' 4 tal work where radium is used. 'Ihis extremely expensive material is generally enclosed in needles or tubes which are easily lost in the dressings where it is disagreeable and painful to look for them. The apparatus according to the invention will at once detect an innitely small mass of radium among a large amount of other material.

Finally the apparatus easilylends itself to quantitative meurements of radiant sources. by the previous calibration of the micro-ammeter in- Serted in the plate circuit.

What we claim as our invention and desire secure by Letters Patent of the United States is:

1. In an automatic nre alarm system, an alarm device, a photosensitive Geiger counter tube responsive only to light radiations of wave-lengths below approximately 3,000 Angstrom umts, said tube being characterized in that it supplies internally amplified current pulses for individual light quanta and comprises an envelope at least a portion of which is permeable to said light radiations, a cathode within said envelope having a photo-electric surface responsive to said light radiations, an anode wire within said envelope in cooperative association with said cathode, a gas lling within said envelope to eiect Geiger counter operation of said tube when a predetermined potential is applied to the electrodes, means for integrating said current pulses with reference to a predetermined time constant so as to produce a summation whose magnitude at any instant is dependent upon the average rate ci occurrence of said pulses, and means for actuating said alarm device when the magnitude of said summation reaches a predetermined level.

2. In a light radiation responsive apparatus, a photosensitive counter tube responsive only to light radiations of wave-lengths below approximately 3,000 Angstrom units, said tube being characterized in that it supplies internally amplined current pulses for individual light quanta and comprises an envelope at least a portion of which is permeable to said light radiations, a cathode within said envelope having a photoelectric surface responsive to said light radiations, an anode within said envelope in cooperative association with said cathode, a gas filling withinv to the end that said summation may be caused to perform some useful function when it reaches a predetermined level.

ALEXANDRE DAUVILLIER.. MAURICE PONTE.

REFERENCES CITED The following references are of record in the ille of this patent:

s hotoelectric Cells, Campbell, London, 1929, DP. rinato-Electricity, Auen, Londen. 1913. pp. 1, 2.

Counters, Locher, Radiology, v. 27, 1936, pp. 149-157.