GB2032774A - Fire extinguisher - Google Patents

Abstract

A fire extinguisher which releases vapours of an extinguishing agent in response to infra-red radiation reaching the container. The infra-red radiation activates a fuse (3) which, in turn, optionally activates a thermal charge (7) and the heat that results destroys a container (4) which encases a liquid fire extinguishing agent (2). The extinguishing agent then vaporizes and issues from the extinguisher. <IMAGE>

Description

SPECIFICATION Fire-extinguisher The present invention relates to a fire extinguisher and a method of extinguishing a fire which are particularly useful in enclosed spaces, for example stationary depots, laboratories, and baggage and engineering compartments of transport facilities.

The present invention consists in a fire extinguisher which comprises: a container containing one or more thermoplastic capsules containing an extinguishing agent as a liquid, and one or more fuses responsive to infra-red radiation from outsidethe container; the infra-red radiation causes the or each fuse to give rise to heat which destroys the or each capsule causing the capsule to release gaseous extinguishing agent. If the extinguishing agent is a gas at ordinary pressures and is maintained as a liquid in the capsules by pressure, it will be neces sary for the heat simply to break the capsules.If this is not the case, the heat must be sufficient to vapourize the extinguishing agent The extinguishing agent is preferably a chemically active inhibitor, and we prefer freons, for example bromochlorodifluoromethane and tetrafluorodibromoethane, and compositions based on ethyl bromide or on methylene bromide.

Reaction of the fuses after activation by infra-red radiation may directly produce the heat required to destroy the capsules. Alternatively, a charge may be provided which is activated by the fuse, and in this case the necessary heat is provided by the burning charge. The fuse or the charge or both the fuse and the charge may consist of one or more rods of material, and any rods or charge material are preferably contained in perforated sleeves which have at least one end open to allow the charges to be activated by the fuses. The charge rods or other charge material preferably consists of a highly inflammable oxygen-containing composition.

The fire extinguisher of the invention preferably additionally comprises a one-way valve between the fuse and the charge, allowing passage of gas only towards the charge.

The shape of the container is not particularly critical, but we prefer that it has at least one flat surface so that it can be easily attached to a wall or a ceiling.

A hemisphere is a particularly preferred shape. The container is preferably perforated (preferably over substantially all of its exposed surface) in order to allow easy escape of gaseous extinguishing agent.

The fuse or fuses may be arranged in any way so long as they are able to respond to infra-red radiation reaching the container from a fire. The or each fuse preferably extends from the container, and the portion extending is preferably enclosed in an envelope of a highly heat-conducting material.

The extinguishing agent retains its effectiveness after prolonged storage in ordinary capsules-spe- cial sealed vessels are not required. The preferred size of the capsules will depend on the particular use to which the extinguisher is put, and in any case the size is not particularly critical; however, for most purposes miniature capsules are by far the best. The material of the capsules may be any thermoplastic material which will rapidly break or otherwise be destroyed under the influence of the fuse or charge.

When the capsules are destroyed the chemically active inhibitor or other extinguishing agent rapidly vapourizes thereby distributing itself around the fire extinguisher. A closed compartment that has been supplied with the correct number or size of exting uisherwill soon become sufficiently full of extinguishing agent for the fire to be rapidly extinguished and for a new fire to be prevented for a definate period of time which will depend upon the rate of ventilation of the compartment. The extinguisher of the invention therefore provides a reliable means of fire fighting with the minimum consumption of extinguishing agent.

We have found thatfreons are particularly good extinguishing agents since, even at normal temperatures, they revert rapidly to the gaseous state with a considerable increase in volume after rupture of the capsules. Hence a compartment can be filled with a non combustible atmosphere by using only small amounts of the extinguishing agent.

It is preferable that the liquid freon or other extinguishing agent is confined in the miniature capsules under pressure since this causes the capsules to break more intensively, thereby distributing the agent throughout the compartment more effectively.

The thermal charge is preferably situated completely within the container. Also, we prefer that the charge is contained within a perforated sleeve having at least one (preferably only one) end open, the opened end preferably being secured to a fuse. This arrangement ensures that the thermal energy of the thermal charge is used most effectively to break the miniature capsules.

As mentioned above, it is desirable that a one-way valve is provided between the fuse and the charge.

The function of this valve is to eliminate leakage of combustible gases beyond the container and to allow the thermal energy of the charge to be used more completely to break the material of the minature capsules and thus to evaporate the extinguishing agent.

Each thermal charge and each fuse are preferably made in the form of rods, and this also increases the efficiency of the extinguisher and simplifies its design. The fuses may be enclosed within an envelope of a highly heat-conducting material which should not, of course, interfere with ignition of the fuse or prevent discharge of hot gases into the container.

To summarise, the extinguisher of the invention is particularly useful in an enclosed compartment, it is able to quench fires quickly, it requires less extinguishing agentthan many other designs, it is reliable in operation, and it obviates the need for intermediate links.

The invention is further illustrated by the accompanying drawings in which; Figure lisa partly sectional view of an extinguisher of the invention; Figure 2 shows a similar extinguisher to that shown in Figure 1, but with a different arrangement of fuse; and Figure 3 shows a similar extinguisher to that of Figures 1 and 2, but including a one-way valve between the thermal charge and the fuse.

Container 1 should be placed in any suitable position within the compartment to be protected from fire. Container 1 contains a fire extinguishing agent 2, and a fuse 3 placed outside container 1 in a position to respond to infra-red radiation reaching the extinguisher from a fire.

The fire extinguishing agent 2 is preferably a chemically active liquid inhibitor which exerts an active influence on the chemical reactions involved in combustion, for example by scavenging or otherwise reacting with combustion products, and this is accompanied by a considerable absorbtion of heat.

Preferred active liquid inhibitors include halogenbased combinations containing fluorine, chlorine, or bromine. Specific examples of chemically active inhibitors are freons (such as bromochlorodifluoromethane and tetrafluorodibromoethane and compositions based on ethyl bromide or on methylene bromide. Other suitable extinguishing agents known to those skilled in the art may also be used. The particular chemically active inhibitor or other extinguishing agent chosen will often depend on the particular conditions, such as living quarters, depots, cargo containers, and baggage or engineering compartments of transportation facilities, in which the extinguisher is to be used. For convenience, however, the following embodiment will be described with reference only to freons.

For ease of storing, the freon is held in container 1 under pressure in miniature capsules 4 made from a thermoplastic material, such as gelatine. It is necessary that the freon is distributed throughout the compartment to be protected whenever a fire arises.

The amount of heat required to vapourize the freon will depend, of course, on which freon is used. This change from liquid to gas may occur spontaneously on rupture of the capsules or it may be necessary that the temperature in the container rises. This increase in temperature in the container is achieved by choice of suitable fuse andior thermal charge. The particular fuse andlorthermal charge chosen will depend on the particular extinguishing agent and on the particular conditions under which the extinguisher is used, and various suitable fuses and thermal charges are known to the skilled man.

The following description is of a typical extinguisher according to the invention and suitable for use in an enclosed compartment. The number of such extinguishers that should be used in any compartment will depend on the risk of fire and on the arrangement of objects within the compartment that are particularly vulnerable to fire.

A dome-shaped container 1 having a flat cover plate 5 contains a suitably arranged extinguishing agent 2. Container 1 may be secured with cover plate 5 flat against a wall or ceiling of the compartment by means of any conventional fastener through holes 6.

A fuse 3 is provided outside container 1 and a charge which will distribute the extinguishing agent throughout the compartment is provided inside the container and in contact with the fuse. The fuse 3 is preferably made from an oxygen-containing material, and suitable explosive compounds, preferably powdered, known to the skilled man may be used.

The explosive compound will ignite as the temperature in the compartment rises above a certain value.

The chemically active inhibitor, which may be any of those exemplified above, is confined under pressure in miniature capsules 4 provided in container 1.

The capsules may be made from any suitablethermoplastic material that will melt quickly when the temperature in the container 1 rises. Suitable materials are known to the skilled man.

In Figures 1 and 3 a thermal charge 7 separate from the fuse is provided. The thermal charge is in the form of a rod manufactured from a conventional highly inflammable oxygen-containing substance which, on ignition of fuse 3 raises the temperature in the container thereby melting miniature capsules 4 and vapourizing the freon. In this case, the burning fuse 3 is simply a means of igniting the thermal charge 7, and it is the thermal charge which raises the temperature in the container sufficiently to break the material of the miniature capsules 4.

It is, of course, necessary that gaseous freon be able to escape from the container. The container is provided with holes 8 having a diameter less than that of the miniature capsules 4.

In this embodiment the thermal charge 7 is placed in a perforated sleeve 9, and this results in a more uniform action of the burning charge on the miniature capsules 4. One end of the perforated sleeve 9 faces cover plate 5 of the container 1, and the other end of the sleeve is open and extends from container 1. The side walls and the closed end of sleeve 9 are perforated with holes 10. Sleeve 9 is preferably secured in container 1 by means of a threaded joint on the external surface of the sleeve which mates with a thickened portion 11 of container 1.

The open butt end of sleeve 9 is designed to secure fuse 3. This can be done by means of a threaded joint and a flat cover plate 12 as shown in Figure 2, or by means of a hemispherical shell 13 as shown in Figures 1 and 3. A spacing washer 14 is used to retain thermal charge 7 in sleeve 9.

The extinguisher shown in Figure 3 includes a one-way valve 15 between thermal charge 7 and fuse 3. This valve allows passage of gases only towards thermal charge 7. The valve is provided with a disc 16 having holes 17, and in the central part of disc 16 above holes 17 are secured spring tabs 18 which open the holes under the action of hot gases liberated by the combustion of fuse 3. In Figure 3 the tabs 18 are shown in the raised position. The oneway valve 15 prevents hot gases escaping from sleeve 9 through its open butt end during combustion of thermal charge 7.

Figure 2 shows an extinguisher according to the invention which does not have separate thermal charge and fuse; one piece of material (7, 3) in the form of a rod extends from sleeve 9 and is held in the sleeve by a flange 19 of flat cover plate 12.

In Figures 1 and 3 the container 1 is provided on its outside with several rod-shaped fuses 3 secured by means of, for example, a threaded joint in holes of a hemispherical shell 13. In this case the rod-shaped fuses 3 may be in contact with thermal charge 7, and this arrangement is shown in Figure 1. Alternatively, there may be a space between the fuse and the charge as shown in Figure 3. This space should not be so great that rapid ignition of thermal charge 7 is prevented; the heat from the burning fuse must be transmitted with no difficulty to thermal charge 7.

The part of the or each fuse 3 that extends from container 1 is preferably enclosed in an envelope 20 made from a highly heat-conducting material, such as copper, of about 0.1 mm thickness.

Briefly, the extinguisher of the invention operates in the following way. When the temperature in an enclosed compartment in which the extinguisher is situated rises above a particular value or when an open flame occurs, the or each fuse 3 ignites causing thermal charge 7 to catch fire. When this takes place, hot gases released from thermal charge 7 escape through holes 10 of the sleeve 9 into container 1, causing the temperature in container 1 to rise sharply. This causes the material of the miniature capsules 4 to melt and the liquid freon within the capsules to vapourize. As the thermal charge 7 con tinges to burn, the material of the miniature capsules is destroyed.

This vapourization of freon causes the pressure in container 1 to increase, and gaseous freon therefore escapes through the holes of the container thereby filling the compartment. As the compartment fills with the non combustible freon atmosphere the fire is stifled.

A non combustible atmosphere may be produced in the compartment even if the rise in temperature within the compartment does not cause the fuse or thermal charge to ignite. In this case, the material of the miniature capsules is destroyed simply as a result of the higher temperature within the compartment. Again, liquid freon vapourizes and its vapours escape through the holes in the container, thereby producing a non combustible atmosphere in the compartment. It is of course possible to use the extinguisher of the invention in conjunction with conventional extinguishers or in conjunction with conventional fire warning systems.

Claims (14)

1. Afire extinguisher which comprises: a container containing one or more thermoplastic capsules containing an extinguishing agent as a liquid, and one or more fuses responsive to infra-red radiation from outside the container; the infra-red radiation causes the or each fuse to give rise to heat which destroys the or each capsule causing the capsulk to release gaseous extinguishing agent.

2. An extinguisher according to claim 1, in which the extinguishing agent is a chemically active inhibitor.

3. An extinguisher according to claim 2, in which the chemically active inhibitor is a freon.

4. An extinguisher according to claim 3, in which the freon is bromochlorodifluoromethane, ortetraf luorodibromoethane.

5. An extinguisher according to claim 2, in which the chemically active inhibitor is a composition based on ethyl bromide or on methylene bromide.

6. An extinguisher according to any one of the preceding claims, in which the fuse comprises one or more fuse rods and reaction of the fuse rods directiy produces the heat.

7. An extinguisher according to any one of claims 1 to 5, in which the fuse activates a charge and the charge reacts to produce the heat.

8. An extinguisher according to claim 7, in which the charge comprises one or more charge rods of a highly inflammable oxygen-containing composition.

9. An extinguisher according to claim 8, in which the or each charge rod is contained in a perforated sleeve having at least one end open, the open end being provided with one or more of the fuses.

10. An extinguisher according to any one of claims 7,8 and 9, which additionally comprises a one-way valve between the fuse and the charge, allowing passage of gas only towards the charge.

11. An extinguisher according to any one of the preceding claims, in which the container is a perforated hemispherical shell.

12. An extinguisher according to any one of the preceding claims, in which the or each fuse extends from the container, and the portion extending from the container is enclosed in an envelope of a highly heat-conducting material.

13. An extinguisher according to claim 1, substantially as herein described with reference to the accompanying drawings.

14. A method of extinguishing a fire in an enclosed compartment, in which an extinguishing agent whose function is effected by a liquid chemically active inhibitor confined in miniature capsules of a thermoplastic material is situated in the compartment in an individual container fitted with a fuse responding to infra-red radiation; said extinguishing agent being distributed over the compartment after ignition of the fuse by changing the chemically active inhibitor from a liquid to a gas under the influence of the temperature rising in the container after ignition of the fuse, destroying the material of the miniature capsules and evaporating the inhibitor, whose vapours escape from the container and produce a non combustible atmosphere in the compartment.