FOAM/WATER/AIR INJECTOR MIXER
FIELD OF THE INVENTION
This invention relates to injector/mixers, and will? have special application to mixers of foam, air, and water in the fire fighting industry.
BACKGROUND OF THE INVENTION
Compressed Air Foam Systems (CAFS) have recently gained popularity with many different types of firefighting organizations. The reason is simple. Foams are more effective in both putting out and controlling the spread of most fires. Foams are also cheaper to use 15 than simply dousing a fire with water and also save the building owner a considerable amount in water damage. Also foams come in many classifications which work efficiently against all of the common types of fires.
One problem which has been of great concern to 20 users of CAFS is the creation of turbulence in the delivery line at a point just downstream of the air injection port. Since air must necessarily be injected into the line at some point to ensure proper expansion of the foam, the problem of turbulence needed to be solved, since the 25 delivery of the foam was impeded due to energy loss.
All previous attempts at solving the turbulence problem failed to some degree. These attempts included air injection at right angles relative to the water/foam flow, air injection at oblique angles, and mixing in vari- 30 ous so-called motionless mixers such as the labyrinth, the perforated plate, the orifice and the modified orifice. While these mixers reduced the turbulence in the line, significant energy loss still occurred with the resulting loss of pressure and throw distance at the nozzle end.
More information about the general principles of CAFS can be found in the attached report of the U.S. Department of Agriculture.
SUMMARY OF THE INVENTION 40
The injector/mixer of this invention includes an eductor positioned in flow communication between the water pump and the hose. The eductor includes ports for the introduction of foam solution and air into the water stream. Inside the central bore of the eductor is an insert which has a tapered bore and a plurality of peripheral holes in communication with the air injection port.
As the water flows through the tapered portion of the 5Q insert bore, a venturi-like effect is created. Injection of foam and air at the point where the bore tapers almost totally eliminates the turbulence in the line due to the increased velocity and lowered pressure of the stream through the tapered section of the bore. Mixing is also 55 enhanced which results in more effective foam production.
As the water/foam/air mixture exits the eductor, the foam generated from the mixing passed through a flared connector, and then into the fire hose for delivery 60 through a nozzle. Preferably, the foam is of the approximate consistency of shaving foam and is delivered through the nozzle with little energy loss due to turbulence.
Accordingly, it is an object of this invention to pro- 65 vide for a water/foam/air mixer which promotes efficient mixing delivers consistent foam solution to the nozzle.
Another object is to provide a water/foam/air mixer which reduces energy loss in the hose due to turbulence.
Another object is to provide a water/foam/air mixer which is efficient no matter what size and delivers predictable pressure and throw distance at the nozzle end.
Still another object is to provide a water/foam/air mixer which can be used with currently available firefighting equipment.
Still another object is to provide a water/foam/air mixer which may be efficiently used with all types of foam solutions and mixer ratios.
Other objects will become apparent upon a reading of the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of an air injection mixer constructed according to the principles of this invention.
FIG. 2 is a sectional view of a combination water/foam/air injection mixer.
FIG. 3 is a sectional view of a modified air injection mixer according to the principles of this invention.
FIG. 4 is a schematic depiction of a firefighting apparatus utilizing the mixer of FIG. 1.
FIG. 5 is a schematic depiction of a firefighting apparatus utilizing the combination mixer of FIG. 3.
FIG. 6 is a schematic depiction of the apparatus of FIG. 4 but illustrating a naturally aspirated air mixer.
DESCRIPTION OF THE PREFERRED
The preferred embodiments herein described are not intended to be exhaustive or to limit the invention to the precise forms disclosed. They are chosen and described to explain the principles of the invention and its application and practical use to enable others skilled in the art to utilize its teachings.
Referring first to FIGS. 4-6, reference numerals 10, 10', and 10" refer generally to a firefighting apparatus with the delivery system shown in schematic form. Each apparatus 10 includes water supply 14 pump 12 conduit 16, fire hose 17 and discharge nozzle 18. The above description applies to nearly all firefighting vehicles in use today.
FIG. 4 illustrates the use of the current invention in combination with system 10. In this embodiment, an eductor 20 is connected in flow communication along conduit 16 and is connected to a supply of foam concentrate 22. The foam concentrate 22 may consist of any of the available foams which are used in fighting varying types of fires. A metering valve 24 is connected between foam supply 22 and eductor 20 to allow firefighters to visually observe that the specified concentration of foam is being introduced into the eductor 20.
An air injection mixer 26 is connected in flow communication to conduit 16 downstream of eductor 20. A supply of compressed air 28 is connected to mixer 26 and supplies pressurized air into conduit 16. An air metering orifice 30 is connected between air supply 28 and mixer 26 to ensure that the air pressure at the mixer 26 is kept at the proper level. Eductor 20 and mixer 26 are separated by an adapter 32 in this embodiment. Heat exchanger 34 is optionally placed between water supply pump 12 and eductor 20 to heat the water if desired.
System 10 operates to deliver foam under pressure through discharge nozzle 18 to fight various types of fires. As water is pumped through conduit 16 into eductor 20. a quantity of foam concentrate is continuously mixed into the water, with the exact quantity preset by the firefighter to be checked at metering valve 24.