US2760586A - Explosion suppression - Google Patents

Description

E. D. REDDAN EXPLOSION SUPPRESSION Filed April 14. 1954' IN V E N TO R EDWIN D. REDDAN ATTOR N E Y EXPLOSIUN SUPPRESSION Edwin D. Reddan, Wellesley, Mass., assignor to Electronics Corporation of America, a corporation of Mas sachusetts Application April 14, 1954, Serial No. 423,194

2 Claims. (Cl. 169-28) This invention relates to extinguishing devices of the type comprising a container for an extinguishing agent and a detonator arranged to burst the container and scatter the extinguishing agent in the presence of a fire or of an incipient explosion.

As compared with the explosion of a substance which carries its own oxygen, an explosion of a mixture such as that of air and gasoline has the characteristic that the rate of development of pressure is relatively slow; thus, for example, an explosion of a mixture of air and paraffin spray make take .2 to .3 second to develop a maximum pressure of about 40 to 60 pounds per square inch; and gasoline vapor in free air develops a pressure of about 80 pounds per square inch approximately .04 second after ignition.

Thus an explosion of a mixture of a combustible vapor with air begins with a relatively slow build-up of energy, with correspondingly slow rises of pressure, heat, and radiation. This rise may be spread over several hundredths of a second before a critical energy level is reached and a dangerous explosive pressure is developed.

An explosion detector and suppressor system has been proposed in which the detector comprises a pressureresponsive diaphragm which detects the rise in pressure occurring in an incipient explosion. This detector is connected in an electric circuit including a contact adapted to be closed by the detector to release an extinguishing agent. The detector is made to respond to a small pressure rise when the rate of pressure rise is in excess of 50 pounds per square inch per second, and is capable of closing the contact within .02 second of the initiation of the pressure rise. The suppressor is capable of distributing the extinguishing agent within .05 second of the initiation of the pressure rise. The suppressor comprises a frangible container for the extinguishing agent. A rapidly-acting detonator, which acts in response to the closing of the detector contact, is arranged to burst the container and thus scatter the extinguishing agent which it contains. This system is described in detail in British Patent No. 643,189, published September 15, 1950.

Another explosion detector has been proposed which is responsive to the rate of rise of electromagnetic radiation which occurs in an incipient explosion. This explosion detector comprises a photocell the output of which is connected to an electronic valve through a differentiating network. This valve, which is normally nonconductive, conducts when the photocell detects a sharp rise of radiation of the type found in incipient explosions. Conduction through the valve actuates the explosion suppressor. This explosion detector of the radiation type is described in United States Patent Application Serial No. 364,142, filed June 25, 1953, by Bradford T. Joyce and Alfred F. Krueger, and entitled Explosion Detection and Suppression.

A typical application of these explosion detector and suppressor systems lies in the protection of fuel tanks, particularly those of military aircraft which may be penetrated by incendiary bullets. When this occurs, the fuel 2,760,586 Patented Aug. 28, 1956 vapor in the tanks is ignited and explodes, fracturing part of the aircraft structure or wing and scattering burning fuel over it, causing the aircraft to come down in flames.

In suppressors designed to protect the fuel tanks of aircraft, the container for the extinguishing agent must be made of a material which is not attacked by the fuel or by the extinguishing agent. Also, when the suppressor is operated, it must not burst into fragments of such small size that they might clog the fuel system of the aircraft.

One suitable suppressor comprises a relatively stifi backing plate which includes a housing for a detonator. A frangible, phenolic-impregnated fabric hemisphere is securely attached to the backing plate, forming a sealed cavity in which the extinguishing agent is placed. When the detonator is blown, the hemisphere breaks into relatively large pieces, and the extinguishing agent is scattered throughout the protected tank as a fine mist. While this type of suppressor is sufliciently tough not to be shattered by exploding another suppressor of the same type in its vicinity, it has, in some instances, been shattered by fragments of incendiary bullets before an explosion detector of the pressure-rise type could detect the incipient explosion. Such a premature shattering of the suppressor resulted in failure to suppress the explosion, as the proper distribution of the extinguishing agent through the tank can only be obtained by shattering the suppressor by means of the detonator.

It is the principal object of this invention to provide an explosion suppressor which does not shatter prematurely when hit externally by flying fragments, which ruptures when the pressure inside the suppressor is increased by the firing of the detonator and thus scatters the extinguishing agent which it contains, and which does not rupture into pieces small enough to clog an aircraft fuel system.

In accordance with the illustrated embodiment of the present invention, the container for the extinguishing agent is made of a material the flexibility of which is such that the container may be visibly deformed when pressure is applied to it by hand, the container resuming its normal shape when the pressure is removed.

Referring to Figure 1, the explosion suppressor comprises a container 3 for the extinguishing agent 5. This container 3 is made of a highly flexible material such as the polymonochlorotrifluoroethylene plastic sold by the M. W. Kellogg Company under the trademark of KEL-F. The container 3 is provided with a threaded neck portion 7. After the container is filled with the extinguishing agent 5, it is sealed by means of a hollow plastic stopper 9 which fits inside and over the neck portion 7 of the container 3 and is heat-sealed thereto. The hollow stopper 9 is longer than the neck portion 7 of the container 3. A detonator 11 is positioned in the stopper 9, the explosive charge of the detonator being preferably located toward the bottom of stopper 9. The neck portion 7 of the container 3 is screwed into the metal socket 113. The detonator 9 is provided with a shoulder portion 15 and with two male contacts 17 which fit into two female contacts 19. Female contacts 19 are electrically connected by means of wires 20 to outside terminals 21. For mounting purposes, the socket 13 is provided with a flange 23 which may be secured by means of rivets passed through holes 25 to the wall of an aircraft fuel tank.

When a fire or explosion detector fires the detonator, the container 3 bursts and scatters the extinguishing agent 5 which it contains. The highly flexible container 3 does not shatter when hit externally by fragments of an incendiary bullet; at worst it may puncture, in which case by the time the explosion caused by the incendiary bullet is detected and the detonator is fired a sufiicient amount of extinguishing agent is still left in the container 3 to suppress the explosion.

I claim:

1. An explosion suppressor comprising: a sealed eontainer made of a highly flexible material, an extinguish ing agent within said container, and a detonator having an explosive charge positioned within said container.

2. An explosion suppressor comprising: a container made of a highly flexible material and having a threaded neck portion, a hollow stopper longer than said neck portion and sealed thereto, an extinguishing agent positioned within said container, and a detonator having an explosive charge positioned within said hollow stopper.

References Cited in the file of this patent UNITED STATES PATENTS Delbare Apr. 24,

Buddecke Apr. 9,

Thompson Oct. 5,

FOREIGN PATENTS Great Britain Sept. 15,

Claims (1)

1. AN EXPLOSION SUPPRESSOR COMPRISING: A SEALED CONTAINER MADE OF A HIGHLY FLEXIBLE MATERIAL, AN EXTINGUISHING AGENT WITHIN SAID CONTAINER, AND A DETONATOR HAVING AN EXPLOSIVE CHARGE POSITIONED WITHIN SAID CONTAINER.

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