Fire extinguishers – Fluid systems – Plural source – mixing in transit
Patent
1996-04-04
1998-08-04
Hoge, Gary C.
Fire extinguishers
Fluid systems
Plural source, mixing in transit
A62C 3112
Patent
active
057879893
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/NO 94/00103, filed Jun. 3, 1994.
FIELD OF THE INVENTION
The present invention concerns an apparatus for producing fire-fighting foam, a foam generator.
The apparatus has an air inlet and consists of a fan which is operated by a reaction jet motor and a foam net which can be made of a perforated plate. The reaction jet motor has nozzles and is connected to a liquid under pressure. The liquid is usually water to which a foaming agent has been added.
When the liquid is sprayed from the nozzles the reaction forces will operate the fan. At the same time the nozzles will atomize the liquid and spray it against the foam net. The air from the fan blows the liquid through the foam net thus generating foam.
BACKGROUND OF THE INVENTION
From Norwegian patent no. 120 715 there is known a similar apparatus which is operated by a reaction jet motor, for producing fire-fighting foam.
In U.S. Pat. No. 3,999,612 there is disclosed a foam generator where a tilted baffle plate is located outside the nozzles. The baffle plate will deflect the jets of liquid, thus distributing the liquid evenly over the foam net. However, the jets of liquid are not atomized by the baffle plate.
In a foam generator it is desirable to produce as much foam as possible with a high expansion ration in the shortest possible time.
The expansion ratio is usually expressed as how many times a quantity of liquid increases in volume when it is converted into foam. An expansion ratio of 1,000 is achieved when 1 liter of water is converted into 1,000 liters of foam. The fan's rotation speed is crucial for the velocity of the air flow and the volume of air which forces the liquid through the foam net.
An increase in fan speed can be achieved by using nozzles with short moment arms and/or by employing a higher water pressure.
If the water pressure is too great, however, the disadvantage arises that the water jet strikes the foam net with such force that it breaks up its own foam and the foam production is reduced. Known foam generators are encumbered with this defect, and they therefore normally do not operate with a water pressure high than 5 bar.
Another drawback with known foam generators is that the water has to be atomized by the nozzles before it strikes the foam net. If the water is not sufficiently atomized the generator does not produce light foam, i.e. foam with a high expansion ration.
It is known in the prior art to employ nozzles which are designed in such a manner that they atomize water. In addition the nozzles are also constructed in such a way that they disperse the water in a fan shape, so that the water covers the entire foam net. A further flaw in some designs of known foam generators is that the foam net is located in such a manner that the nozzles have to be tilted in relation to the shaft in order for the water jet to be able to cover the entire foam net.
Thus the known foam generators do not take maximum advantage of the available water energy. Atomizing nozzles which also disperse the water in a fan shape, and nozzles which are tilted in relation to the shaft will substantially reduce the thrust. In the case of nozzles tilted at an angle of 45, e.g., the thrust is reduced by approximately 50%, thereby reducing the fan's speed and volume of air. This results in a low foam production.
SUMMARY OF THE INVENTION
The object of the present invention is to avoid the above-mentioned drawbacks.
This problem is solved according to the invention by means of an apparatus which effectively achieves maximum utilization of the available water energy and which is characterized by the features in the claims presented.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in more detail with reference to the drawings which illustrates an embodiment of the apparatus, only the principles of the invention being illustrated.
FIG. 1 is a sectional elevation of a foam generator.
FIG. 2 is a section taken after line A--A in FIG. 1.
DETAILED DESCRIPTION OF THE INVENTI
REFERENCES:
patent: 3393745 (1968-07-01), Durstewitz
patent: 3428131 (1969-02-01), Winslow
patent: 3441086 (1969-04-01), Barnes
patent: 3446285 (1969-05-01), Hout
patent: 3607779 (1971-09-01), King et al.
patent: 3780812 (1973-12-01), Lambert
patent: 3999612 (1976-12-01), Noguchi
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