The present invention relates to fire extinguishers, and more particularly to fire extinguishers which are capable of operation at any orientation.

Fire extinguishers of the type comprising fluid extinguishant maintained under pressure by a pressurized propellent fluid are conventionally designed for use at a predetermined orientation, the construction being such as to ensure that extinguishant, rather than propellent, is discharged through an outlet head when an outlet valve is opened. There have been proposed extinguishers for operation in any orientation in which the extinguishant is contained in a flexible bladder

within the body of the extinguisher, the propellent being within the body externally of the bladder. The bladder communicates directly with the outlet head so that the extinguishant is always discharged to the head irrespective of the orientation. Whilst this is satisfactory for some applications, the deformation of the bladder during discharge provides unpredictable discharge characteristics. This system is unsuitable for applications where it is essential for the extinguishant to be released within a few milliseconds, as is required for certain military uses. Also, the extinguishant does tend to erode..the bladder over a period of time. For some military applications it has been proposed to mount a conventional rapid discharge extinguisher in a mounting system which ensures that the body of the extinguisher will always remain in the same orientation irrespective of changes in the altitude of the structure, such as the body of a tank, to which the extinguisher is attached. Such a mounting system will usually involve the use of gimbles and is not only expensive and adds weight but may also not be totally reliable in adverse circumstances as may be encountered in battle conditions.

According to the present invention, there is provided a fire extinguisher capable of operation in different orientations, comprising a first pressure vessel for containing propellant, a second pressure vessel for containing extinguishant, a discharge valve communicating with an end of the second vessel for discharge of extinguishant therefrom, and means for permitting flow of propellent from the first vessel into the second vessel at a position remote

from the discharge valve whereby to permit pressurisation of the extinguishant therein while preventing extinguishant flow from the second to the first vessel.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawing the sole figure of which is a sectional view of the extinguisher in accordance with the preferred embodiment.

The extinguisher 1 shown in the drawing consists of a body 2 forming an outer pressure vessel, and an outlet head 4. The body 2 houses a rigid inner pressure vessel 6 which divides the interior of the body into an inner compartment 8 which contains extinguishant and which communicates directly with the outlet head 4, and an outer compartment 12 which contains propellent under high pressure. The inner and outer compartments are connected at the base of the inner vessel remote from the outlet head 4 by a one-way valve 14 which permits fluid flow only from the outer to the inner compartment. In the embodiment shown, the valve 14 is a spring-loaded valve which opens in a direction towards the inner compartment 8, although other forms of the valve may also be used. The extinguisher also comprises a filler valve 16 to admit extinguishant fluid directly into the inner compartment 8 and a pressurizing valve 18 to admit high pressure propellent gas directly into the outer compartment 12.

The outlet head 4 comprises a discharge valve 19 which normally closes an outlet passage 20

from the inner vessel. In the embodiment shown, the discharge valve 19 is in the form of a plug within the outlet passage 20. The head of the plug is sheared upon activation of an electrically detonated explosive charge 22 to provide rapid opening of the valve. The outlet head 4 may alternatively comprise other forms of rapid opening discharge valve. Preferably, the outlet head 4 and inner vessel 6 are formed as a single, integral, unit, and the body 2 is mounted on the unit, as shown by means of a threaded connection.

Extinguishant fluid to the required weight, is admitted into the inner compartment 8 via the filler valve 16. High pressure propellent gas is admitted into the outer compartment 12 via the pressurizing valve 18 and which by means of the one-way valve 14, equalizes the pressures in both inner and outer compartments 8, 12 and thereby pressurizes the extinguishant to propellent pressure. Upon equalization, the one-way valve 14 effectively isolates the compartments whereby the extinguishant is retained within the inner compartment irrespective of the orientation of the extinguisher. A relief valve 24 leading from the inner compartment 8 enables excess pressure relief of the extinguishant, which may result from temperature fluctuations within the extinguisher. Upon release of the discharge valve 19, the extinguishant starts to discharge and the resulting pressure difference between the inner and outer compartments results in the opening of the one-way valve 14. This causes the pressurised gas to attempt a pressure equalization which results in the rapid discharge of the

extinguishant. This discharge occurs in milli-seconds and is independant of the orientation of the extinguisher.

The embodiment has been described by way of example only, and modifications are possible within the scope of the invention.