The invention is particularly suitable for, but not limited to, a manifold for a compressed air foam (CAF) fire-fighting system.

The manifold may include an aspirator or an injector for the compressed air.

2. Prior Art Compressed air foam (CAF) fire-fighting systems have attracted considerable interest as a small volume of water, mixed with suitable fire-fighting chemicals, can be much more effective, on all types of fires, than large volumes of water alone. For example, in a trial, a CFS fire-fighting system was able to quell a fire of 5000 litres of aviation fuel in 7 seconds.

While the CAF chemicals are expensive, a compact unit with a 500 litre capacity, eg., mounted on a 1-tonne tray top may have a greater fire-fighting capacity than a conventional metropolitan fire tender pumping water.

In areas where limited water is available, or access for large truck-based tenders is not possible, CAF fire-fighting units are particularly suitable.

One problem with existing CAF fire-fighting systems is that the water/chemical mix is not all fully foamed by the compressed air supply. This is believed to be due to a design fault in the existing CAF manifolds, and it may be due to the inability of the injected air to foam the gas when the compressed air pressures drop below, eg., 700-840 kPa (100-120 psi).

SUMMARY OF THE INVENTION It is an object of the present invention to provide a manifold

for a compressed air transfer system which has a longer foaming duration for a given liquid and/or air flow.

It is a preferred object of the present invention to provide such a manifold which can operate over a wider range of compressed air pressures.

It is a further preferred object to provide such a manifold which is relatively inexpensive and simple to manufacture and maintain.

Other preferred objects of the present invention will become apparent from the following description.

In one aspect, the present invention resides in a manifold for a compressed air transfer system, including: a manifold body ; a fluid inlet, at or adjacent one end of the body; a fluid (or foam) outlet, at or adjacent the other end of the body, connected to the fluid inlet by a fluid passage through the body; and a compressed air inlet connected to the fluid passage, intermediate the fluid inlet and the fluid outlet, the longitudinal axis of the compressed air inlet being inclined to the longitudinal axis of the fluid passage, and operable to promote flow (and optional foaming) of fluid flowing through the fluid passage from the fluid inlet to the fluid outlet.

Preferably, the flow of compressed air through the compressed air inlet is substantially concurrent with the flow of fluid through the passage.

In a second aspect, the present invention resides in a manifold for a compressed air transfer system including: a manifold body; a fluid inlet, at or adjacent one end of the body; the fluid (or foam) outlet at or adjacent the other end of the body, connected to the fluid inlet by a fluid passage through the body; and a compressed air injector having an injector body extending

into the fluid passage with an air inlet at one end of the injector body, external to the manifold body, and an air outlet, connected by an air passage through the injector body, within the fluid passage, the flow of compressed air through the injector being operable to promote the flow (and optional foaming) of fluid flowing within the fluid passage from the fluid inlet to the fluid outlet.

Preferably, the longitudinal axis of the injector body (and of the air passage) is c-axial with the longitudinal axis of the fluid passage.

Preferably, the longitudinal axis of the fluid inlet is at substantially right-angles to the longitudinal axis of the fluid passage.

Preferably, the compressed air inlet, or the air inlet of the injector, is connectable to a source of compressed air.

Preferably, the fluid inlet is connectable to a source (eg., a tank) of the fluid to be transferred. In the fire-fighting system, the fluid is preferably a mixture of water and fire-fighting chemicals operable to be converted into a fire-fighting foam.

Preferably, the fluid outlet is connected to a hose, eg., fitted with a fire-fighting nozzle.

In a third aspect, the present invention resides in a compressed air transfer system including: a tank containing a mixture of water and chemicals; a compressed air source; a foam agitator tube in the tank connected to the compressed air source; a pick-up tube in the tank; and a manifold as hereinbefore described having the fluid inlet connected to the pick-up tube and the compressed air inlet, or air inlet of the injector, connected to the compressed air source.

In a fourth aspect, the present invention resides in a compressed air foam fire-fighting system including: a tank containing a mixture of water and fire-fighting chemicals;

a compressed air source; a foam agitator tube in the tank connected to the compressed air source; a pick-up tube in the tank; and a manifold as hereinbefore described having the fluid inlet connected to the pick-up tube and the compressed air inlet, or air inlet of the injector, connected to the compressed air source.

BRIEF DESCRIPTION OF THE DRAWINGS To enable the invention to be fully understood, preferred embodiments will now be described with reference to the accompanying drawings, in which: FIG. 1 is a schematic diagram of a compressed air foam (CAF) fire-fighting system provided with the manifold of the first embodiment of the invention; FIG. 2 is a side view of a portion of the system corresponding to FIG. 1; FIG. 3 is a schematic, part-sectional side view, showing a pick-up tube in a tank; FIG. 4 is a side view of the manifold according to the first embodiment; FIGS. 5 and 6 are respective end and side sectional views of the manifold of FIG. 4; FIG. 7 is a sectional side view of a manifold in accordance with the second embodiment of the invention; and FIG. 8 is a side elevational view of the injector in accordance with the second embodiment of FIG. 7.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 3, the compressed air foam (CAF) fire-fighting system 10 has a tank 11 (eg., of 150-2000 litre capacity) containing a mixture 105 of water and fire-fighting chemicals.

A pair of compressed air tanks 12,13 store compressed air

at, eg., 17500-21000 kPa (2500-3000 psi) and they may be interconnected by a manifold pipe 14.

A tank charge air supply 15 has a tank mounted air inlet fitting 16, connected to the compressed air tank 12 via a regulator valve 17.

A foam agitator tube 104 is connected to the air inlet fitting 16 and has an outlet adjacent the bottom wall of the tank 11. The compressed air released from the foam agitator tube 104 into the tank stimulates the agitator of the water/fire-fighting chemical mixture 105.

A manifold 20 (to be hereinafter described in more detail with reference to FIGS. 4 to 6) is mounted on the tank 11.

An aspirator air supply 18 is connected to the manifold 20 and to the compressed air tank 13 via a regulator valve 19; while a hose 100 (preferably fitted with a fire-fighting nozzle 101) is also connected to the manifold 20.

Referring to FIGS. 4 to 6, the manifold 20 has a manifold body 21 with a fluid inlet 22 provided coaxially within a screw-threaded inlet fitting 23.

The inlet fitting 23 is screw-threadably engaged in a female fitting (not shown) on the tank 11 and the fluid inlet 22 is operably connected to a liquid pick-up tube 102 in the tank 11.

A shown in more detail in FIG. 3, the pick-up tube 102 has a main body portion 106 located a small distance above the bottom wall 11 a of the tank 11, with a pair of transverse branches 107,108.

Holes 109, eg., of approximately 2mm (5/64") diameter are provided in the two branches 107,108 and connecting pipe 110 to allow the mixture 105 to flow to the manifold 20. By selection of the size, number and location of the holes 109, the effective agitation/mixing of the mixture 105, and the duration of the flow of the mixture 105, can be varied/controlled.

Fluid passage 24 extends coaxially within the manifold body from the fluid inlet 22 to a fluid outlet 25. (Preferably, the manifold body is

screw-threaded at 26 to receive a suitable connection fitting (not shown) on the hose 100.) A compressed air inlet 30 has an air passage 31 entering the fluid passage 24 at an angle of, eg., 30° to the longitudinal axis of the fluid passage 24.

The outer end of the air inlet 30 is screw-threaded at 32 to receive a suitable fitting connecting the air passage 31 to the aspirator air supply 18.

In operation, the compressed air foam from the compressed air tank 12 passes through the regulator valve 17 and its pressure is reduced to approximately 1120 kPa (160 psi) to pressurise the water/chemical mixture 105 within the tank 11. Similarly, compressed air from the tank 13 is supplie to the manifold 20 at similar reduced pressure via the regulating valve 19.

When a valve or cap 103 is opened within the hose 103 (or the nozzle 101 is opened), the compressed air pressure within the tank 11 ejects the water/chemical mixture 105 into the manifold 20 via the fluid inlet 22. As the mixture 105 flows through the fluid passage 24 towards the fluid outlet 25, the pressurised air entering the fluid passage 24 via the compressed air inlet 31, both assists in forcing the mixture 105 through the passage 24 and also"foaming"the mixture 105 to form a foam with a volume up to 20 times greater than the volume of the liquid mixture 105.

In tests, it has been found that, compared to existing manifold arrangements, the manifold 20 of the present invention has a duration 2-5 times longer for a given compressed air supply/water/ chemical mixture combination.

Referring to FIGS. 7 and 8, the manifold 120 of the second embodiment has a manifold body 121 where the fluid inlet 122, fluid passage 124 and fluid outlet 125 substantially as hereinbefore described.

A compressed air injector 130 has an injector body 133 screw-threadably mounted in the manifold body 121 where the

compressed air passage 131 is coaxial with the fluid passage 124. The compressed air passage 131 interconnects a compressed air inlet 134, with a fitting connectable to the aspirator air supply 18, to a compressed air outlet 135 provided within the fluid passage 124. The injector body 133 has an inner extension 137 of substantially frusto-conical shape. It is believed that as the water/chemical mixture 105 enters the fluid passage 124 in a direction substantially at right angles thereto (via the fluid inlet 122), a swirling or vortex action is generated which, with the injection of air via the injector 130, enhances the foaming of the water/chemical mixture 105 and so less compressed air may be required to generate the fire-fighting foam which, in turn, enables the foaming action to continue for a longer period, for a given compressed air supply, than for conventional CAF systems.

It will be readily apparent to the skilled addressee that the manifolds can be simply and inexpensively manufactured and can be easily installed and maintained while providing improved performance over existing methods.

Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.