GB2039735A - Fire extinguishers - Google Patents

Abstract

A fire extinguisher comprises a container (1) for containing an extinguishing medium under pressure and has first valve (2) for manual operation of the extinguisher. In order also to provide automatic operation, a second valve (20) is fitted which opens automatically when the temperature exceeds a predetermined level. <IMAGE>

Description

SPECIFICATION Improvements in or relating to fire extinguishers This invention relates to fire extinguishers.

A number of different types of portable handoperated fire extinguishers are known. For example, there are extinguishers comprising a water-filled containter having means for ejecting the water from the container in the directon of the fire. In some cases the water is ejected by a plunger device which breaks a glass bottle containing a charge of sulphuric acid which reacts with sodium bicarbonate previously dissolved in the water. In an alternative type, the water is expelled by carbon dioxide or nitrogen gas liberated from a cylinder inside the container. Another type of fire extinguisher is effective to throw a jet of foam in the direction of the fire. The foam may be generated, for example, by the reaction of aluminium sulphate as sodium bicarbonate in solution.In yet another type of fire extinguisher a vapour-forming liquid (such as carbon tetrachloride -- although use of this chemical has serious disadvantages), or a gas, such as carbon dioxide, stored in liquid form under pressure is directed on to the fire to smother the flames by excluding oxygen.

Many buildings and ships are protected against fire by built-in fire-extinguishing installations.

These normally consist of a series of pipes fitted with special nozzles so that water can be sprayed in any area where a fire occurs. The nozzles are sealed by specially designed valves known as sprinkler heads which shatter when subjected to heat, and permit water to be discharged from the nozzles as a heavy spray.

According to the present invention there is provided a fire extinguisher comprising a container for an extinguishing medium under pressure, and first and second valve means for releasing the extinguishing medium, the first valve means being manually operable and the second valve means being automatically operable in response to an increase in the ambient temperature above a predetermined value.

Although the invention is appiicable in any case where the extinguishing medium is stored under pressure, for example carbon dioxide, or prepressurised water, the use of a non-combustible vapour forming liquid is preferred.

Preferably the liquid in the container is a halogenated hydrocarbon such as bromo-chlorodifluoromethane.

The first valve means may be generally similar to the valve means provided on known manually operated fire extinguishers, and in some applications for example in the case of small appliances for domestic use may be of the controllable discharge multi-shot type. The second valve means may be generally similar to the sprinkler head valves used in built-in-fireextinguishing installations. Conveniently it may include a frangible vessel (e.g. quartz) containing a liquid, such as an alcohol, the vessel being arranged to shatter, and thus open the valve, when the temperature rises above the predetermined value.

In a small fire extinguisher in accordance with the invention it is preferred that the container should be generally cylindrical, and that the first valve means should be located at one end of the container while the second valve means are located at the other end. The first valve means may incorporate a handle for carrying the fireextinguisher and a trigger (or the like) may be incorporated in the handle for manually operating the first valve means. When a fire extinguisher of this type is installed in a vehicle or building, it will be arranged with the first valve means at the top.

and the second valve means at the bottom. Larger fire extinguishers may also be generally cylindrical, or may be spherical. In either case, the second valve means will normally be fitted to the side or in the upper part of the container.

One embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a fire extinguisher according to the invention; and Figures 2 and 3 are longitudinal cross-sections through, respectively, the upper and lower parts of the extinguisher of figure 1.

Referring to figure 1 , the portable fireextinguisher shown comprises a generally cylindrical container 1 for containing, under pressure, an extinguishing medium such as bromo-chloro-difluoromethane (BCF). A first, manually operable valve 2 is fitted to the upper end of the container, whilst at the lower end a second valve 20 is fitted which operates automatically when the temperature exceeds a predetermined level.

The first valve 2 is of conventional construction, and, as can be seen from figure 2 comprises a steel seating 3 crimped to the upper end of the container 1, with a seal 4 of a rubber resistant to the extinguishing medium used. The seating 3 supports a nylon housing 5 in which is slidably mounted a vlave member 6 resiliently urged into sealing engagement with the seal 4 by means of a spring 7. One arm 8 of an L-shaped tube 9 passes through a central aperature 10 in the seating 3 and seal 4 and engages the valve member 6. At the end of this arm 8, within the valve member 14, are apertures 1 liThe other arm 12 of the L- shaped tube 9 forms an outlet mouth or nozzle 13.

A two-part plastics handle 1 4 is secured together by screws (not shown) to grip the upper end of the container 1 at 1 5. Pivotably mounted within the handle is a trigger arm 1 6 which engages the upper surface of the L-shaped tube 9.

In operation, the user grasps the handle 14 and depresses the trigger 1 6. This urges the L-shaped tube 9, and hence the valve member 6 downwardly, so that the extinguishing medium stored under pressure in the container 1 passes up a tube 1 7 secured to the nylon housing 5, through the housing 5, between the valve member 6 and the seal 4, through the apertures 11 and the L shaped tube 9 to issue from the mouth 13, so that the extinguishing medium can be directed onto the fire.

The second valve 20 is shown in greater detail in figure 3, and comprises an aluminium adaptor 21 having a threaded portion 22 and is secured to the extinguisher housing by means of a nut 23 and a fibre washer seal 24. The adaptor has a central outlet passage 25 which terminates in an annular recess for an "O"-ring seal 26 of a rubber resistant to the extinguishant used. The outlet passage 25 is closed by a quartz bulb 27 which is held in position by a deflector housing 28. The housing 28 screws on to an externally threaded portion 29 of the adaptor 21 so as to urge a tapered portion 30 of the bulb 27 into sealing contact with the seal 26.

The quartz bulb 27 is filled with an alcohol, and the wall thickness of the bulb and/or type of alcohol are selected to be such that a temperature rise of the alcohol above a predetermined level causes the bulb to shatter, thus opening the passage 25. The temperature selected will depend on the environment in which the extinguisher is to be installed: as a guide, sprinkler systems typically have threshold temperature in the range 570C to 1750C.

The deflector housing, as can be seen in the drawing, is of generally conical shape, and, in addition to a hollow centre for receiving the bulb 27 has four radially extending openings 31, so that extinguishing medium released from the extinguisher passes through the passage 25, impinges on the lower end 32 of the deflector housing, and is deflected sideways through the openings 31 to provide a wide distribution of the extinguishing medium.

If required, a switch may be provided, responsive to the shattering of the bulb and release of the extinguishing medium, for triggering an alarm. Conveniently, this may take the form of a microswitch mounted in one of the openings 25 so as to bear on the glass bulb in order that the switch contacts be held closed (for example) as long as the bulb remains intact, but open as soon as the bulb breaks. The switch could be connected to an alarm system by means of a suitable quickrelease connector so as not to hinder manual use of the extinguisher. Indeed, with a closed loop alarm system (i.e. with switches normally closed), release of the connector would provide automatic triggering of the alarm in the event of manual operation of the extinguisher.Where the extinguisher is to be wall mounted, the microswitch would usually be fitted in that one of the openings 25 which normally faces the wall.

It will be understood that if one or more fire extinguishers are installed in a vehicle or building, and if a fire occurs in that vehicle or building while it is occupied, the fire extinguisher or extinguishers, may be taken to the site of the fire, and be operated manually, using the first valve to eject vapour from the container tn the direction of the fire through the nozzle. On the other hand if a fire occurs when a vehicle or building is unoccupied, or if the fire occurs so close to the location of the fire extinguisher that it is impossible for the occupant to reach the fire extinguisher, vapour will be expelled through the second valve as soon as the temperature rises above the predetermined value.

Similarly, in very large fires when it is impossible to reach the fire extinguisher, the second valve will open automatically as the temperature rises. This automatic operation is particularly important in high risk fire areas, and one particular advantage is that this can considerably reduce the possibility of pressure vessels exploding.

It will thus be appreciated that the extinguisher described can provide a high degree of protection in a portable, self-contained extinguisher. In addition, the use of separate valves makes for simplicity and ease of construction, particularly since the manually operated first valve can be of conventional construction employing readily available components.

Claims (10)

1. A fire extinguisher comprising a container for an extinguishing medium under pressure, and first and second valve means for releasing the extinguishing medium, the first valve means being manually operable and the second valve means being automatically operable in response to an increase in the ambient temperature above a predetermined value.

2. A fire extinguisher according to claim 1, in which extinguishing medium is a non-combustible vapour-forming liquid stored under pressure in the container.

3. A fire extinguisher according to claim 2, in which the extinguishing medium is a halogenated hydrocarbon.

4. A fire extinguisher according to claim 3, in which the extinguishing medium is bromo-chlorodifluoromethane.

5. A fire extinguisher according to any one of claims 1 to 4, in which the second valve means comprises an aperture closed by a frangible liquidcontaining vessel arranged to shatter above the predetermined temperature thereby to open the aperture.

6. A fire extinguisher according to claim 5, in which the vessel is a quartz bulb containing an alcohol.

7. A fire extinguisher according to claim 5 or 6, further comprising a switch for connection to an electrical alarm system, the switch having an actuating member arranged to bear on the vessel so as to operate the switch upon breakage of the vessel.

8. A fire extinguisher accroding to any one of the preceding claims, in which the first valve means is of the controllable discharge multi-shot type.

9. A fire extinguisher according to any one of the preceding claims, in which the container is generally cylindrical, the first valve means being located at one end of the container and the second valve means at the other end.

10. A fire extinguisher substantially as herein described with reference to the accompanying drawings.