According to a first aspect of this invention there is provided a fire extinguisher comprising a rigid outer casing having an outlet incorporating a release valve, together with an expandable internal bladder communicating with said release valve, the bladder containing a fire extinguishant material, whilst the cavity between the outer casing and the bladder is charged with a compressed gas which will cause the fire extinguishant material to be discharged from the extinguisher when said release valve is opened.

In an alternative aspect the invention provides a fire extinguisher comprising a rigid outer casing having an outlet, together with an expandable internal bladder communicating with said outlet, the bladder containing a fire extinguishant material, whilst the cavity between the outer casing and the bladder communicates with charge of a compressed gas through a release valve such that opening of the release valve will cause the fire extinguishant material to be discharged from the outlet of the extinguisher under pressure of the compressed gas.

Because the driving force to discharge the

extinguishant material is the pressurised gas within the outer casing acting on the internal bladder, the attitude of the fire extinguisher during operation is not important.

Also there is effectively no real pressure loss, so that there is no change in performance as the contents are expelled.

The fire extinguisher could have a flow tube extending through a majority of the length of the extinguisher to provide the communication of the contents of the bladder to the outlet. The flow tube prevents collapse of the bladder onto the outlet from the outer casing, thus allowing the contents of the bladder to escape. Preferably such a flow tube would be formed with perforations down its length to provide substantial communication with the interior of the bladder. However the provision of a flow tube acts as a constriction which, in particular, reduces the rate at which the extinguisher can be filled with fire extinguishant material during manufacture. Also such a flow tube limits to an extent the ability of the extinguisher to operate upside down. As a preferred alternative, therefore, spacer members (for example in the form of bent copper wire structures) can be fitted within the bladder down from the outlet region of the extinguisher.

A separate pressurisation valve can be provided into the outer casing to enable the compressed gas to be injected into the cavity between the outer casing and the bladder.

Whilst the fire extinguisher could be"stand alone" (for example a hand held unit) it is ideally suited for

incorporation into a fire extinguisher system, for example within a vehicle so that the extinguishant from the extin- guisher can be directed to various areas. In this case the fire extinguisher can be linked by a connecting tube to a control box with internal valves which can be opened to allow communication of the contents of the fire extinguisher through an escape valve in the form of a non-return valve to individual outlet tubes which feed the extinguishant material to areas to be sprayed.

The bladder can be formed from a flexible neoprene rubber composite, but is ideally formed from latex rubber and will preferably have a reinforced neck portion.

It is desirable that the rigid outer casing for the fire extinguisher should be moulded as a single piece so that it will have adequate operating strength. It could also be formed from ferrous or non-ferrous material. The casing (and the internal bladder) could be formed to any desired shape so as, for example, to fit into confined spaces.

According to a further aspect of the invention there is provided a method of forming a container in which the container is shaped by laying up fibre material coated in synthetic resin around an expanded and partially pressurised bladder which acts as an internal mould and onto the inner faces of a rigid external mould for forming the outside of the container, further pressurising the bladder to bring the layers of fibre material into intimate contact with one another, curing or setting the synthetic resin to form a

rigid container and deflating and removing the bladder and removing the external mould.

By this means a one piece container can be created.

Whilst the container is ideally suited for use as the outer casing of the fire extinguisher of this invention as defined above, one piece containers for other purposes can also be formed by this method.

Ideally the external mould is of generally curved form on the inner face. The fibre material may comprise fibre- glass or carbon fibre.

The invention may be performed in various ways and preferred embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a sectional view through a fire extin- guisher constructed in accordance with a first aspect of this invention; Figure 2 is a section through the neck of an alterna- tive construction of the fire extinguisher of Figure 1; Figure 3 is a plan view of the bladder of the extin- guisher of Figure 1 or Figure 2 in a collapsed state; Figure 4 is a view similar to that of Figure 1 showing a modification to the extinguisher; Figure 5 illustrates a fire extinguisher system of the invention; and Figure 6 is a cross-section through a device for forming containers in accordance with another aspect of the invention.

The fire extinguisher illustrated in Figure 1 is defined by a rigid outer casing 1 together with a flexible internal bladder 2. A valve 3 mounted in the body of the outer casing 1 provides an interconnection to a flow tube 4 which projects into the bladder 2 and terminates towards the bottom end of the extinguisher. The tube 4 is formed with holes down its length. The body of the casing 1 also includes a pressurisation valve 5.

In use a fire extinguishant material is charged into the bladder 2 (through the holes in the tube 4), thus expanding the bladder so that it moves into contact with the internal walls of the casing 1. The valve 3 is then attached (or an existing valve 3 can be closed) to seal the contents within the bladder 2. A compressed gas is then injected through the pressurisation valve 5 to pressurise the cavity 6 between the casing 1 of the bladder 2.

In use the release valve 3 is operated to allow the contents of the bladder to escape via the flow tube 4. The compressed gas in the cavity 6 causes the bladder 2 to collapse and acts to force the contents of the bladder out of the fire extinguisher. The particular advantage of this arrangement is that operation of the fire extinguisher is generally independent of the attitude of the extinguisher and the operating characteristics remain generally constant during full discharge. Thus, for example, if the extin- guisher was fixed into a vehicle which had overturned, the fact that the extinguisher is upside down would not prevent it from operating adequately to discharge the contents.

This is because the discharge is caused by the collapse of the bladder 2 under the pressure of the compressed gas within the space 6.

In the modified arrangement shown in Figure 2 an insert 7 is provided for insertion into the mouth of the container 1 of Figure 1. This insert 7 is formed with external ribs 8 about which the neck portion 9 of the bladder 2 is pushed.

When the insert is pressed into the neck of the container 1 the neck 9 of the bladder will be firmly held in place.

Extending from the insert 7 are a series of spacer members 10 formed from bent copper wire. These act to prevent collapse of the bladder over the opening to the insert 7 during ejection of the contents of the bladder in use. As can be seen from Figure 3 the bladder 2, in its collapsed state, is folded up so that it can be inserted readily into the outer casing 1. If necessary the opening in the neck of the container 1 can be shaped to accommodate a particular shape of insert which has to be introduced through the neck.

In the arrangement shown in Figure 4 pressurisation valve 5 is remote from the connection into the cavity 6 and associated with a high pressure capsule 5A. The valve 5 can be operated or pierced upon receipt of an electronic signal created by the onset of a fire so that the pressurised gas in the capsule 5A is released and injected into the cavity 6 so that the contents of the bladder 2 are ejected through an outlet tube 12 leading to a point where the extinguishant material is required.

A fire extinguisher system is illustrated in Figure 5

and comprises a fire extinguisher 1 linked to a control box 11 by a connecting tube 12. The control box 11 incorporates a number of valves which will be triggered when a fire is detected to link the tube 12 to a number of outlet tubes 13 which are fed to a number of different areas where it is desired that the extinguishant material should be ejected.

Upon release of at least one of the valves within the control box 11 the extinguishant material within the fire extinguisher 1 will flow out automatically through the non- return valve 3.

Figure 6 illustrates how a container (such as the rigid outer container 1 of the fire extinguisher shown in Figure 1) may be constructed. A rigid external two-part mould 14 is provided together with an internal pressurised bag 15.

The space between the external mould 14 and the bag 15 is filled with a carbon fibre composite material 16, together with a synthetic resin. Firstly the carbon fibre and resin material is laid up over the internal surfaces of the mould 14. Further portions of carbon fibre and resin material are then formed around the partially inflated bag 15. The two halves of the external mould 14 are then placed about the bag 15 and are bolted together. After this the bag 15 is pressurised further to cause the layers of carbon fibre and resin material to be pressed into intimate contact with one another. The moulded material 16 is held in place across the internal surface of the mould 14 by the inflated and pressurised bag 15 as the material within the mould is cured in an autoclave under vacuum. After curing the bag 15 is

deflated (through the inflation opening 17) so that it can be withdrawn from the moulded article. The outer mould 14 is also removed.

As well as forming an outer casing for the fire extinguisher of Figure 1 this process can be used to form containers, bottles etc. of any desired shape and for any preferred purpose. Ideally the moulding will be formed with curves between the walls of the container as the bag 15 can more readily inflate into curved rather than angled corners.