Patent Application
20140352985
1. Field of the Invention
This invention relates to the field of firefighting equipment. More particularly, the invention relates to a compressed air foam system for pumping foam concentrate into a stream of water, aerating the foam-water mixture, and discharging the aerated foam-water mixture through a high-pressure nozzle.
In a further and more specific aspect, the invention concerns a compressed air foam system wherein the amount of air and foam concentrate injected into the system is automatically regulated by the amount of water discharged by the pump.
2. Description of the Prior Art
Water is the best-known but by no means the most effective agent for extinguishing fires. Fires involving flammable liquids and gas, for instance, should never be extinguished with a solid stream of water because this can actually cause the fuel to scatter and the flames to spread. For this reason, various types of foams have been developed for cooling and smothering the flames. In some firefighting systems, the foam is induced by injecting foam concentrate into either the suction side or the discharge side of the fire pump. Other systems induce foam in the hose line through an in-line Venturi, sucking fluid from 5-gallon pails. Still other systems induce foam at the nozzle using the “DDT sprayer” principle, which involves blowing air across a vertical tube leading from the foam receptacle to create a low pressure region, thereby sucking foam out of the receptacle by the Bernouli effect, and then atomizing and spraying the foam.
A major drawback of many prior-art foam dispensing systems is that precise control systems are required to keep the ratio of foam concentrate to water constant. These controls increase the cost and complexity of the systems, making them impractical for use by small, underfunded fire departments.
Accordingly, it is an object of the present invention to provide an system for injecting an additive into a stream of fluid being discharged from a pump and for maintaining the additive at a constant proportion with respect to the fluid, without requiring complex controls.
Another object of the invention is to provide a self-regulating foam-dispensing system that can inject foam concentrate into a stream of water, maintain the foam concentrate and water mixture at a constant ratio, and inject compressed air into the mixture to produce an aerated foam.
Still another object of the invention is to provide a self-regulating foam-dispensing system that is inexpensive to manufacture and can easily be retrofitted into a pre-existing pumping system.
Briefly, to achieve the desired objects of the invention, a pumping apparatus comprising an engine-driven primary pump and a discharge system is provided with a hydraulically driven additive injection system. The additive injection system includes at least one vessel containing an additive, a delivery conduit for transporting the additive from the vessel to the discharge system, and an additive pump for pumping the additive from the vessel to the discharge system via the delivery conduit. The additive pump is preferably a centrifugal pump driven by a hydraulic turbine mounted within the discharge system downstream of the primary pump.
In a preferred embodiment of the invention, the primary pump comprises a fire-engine pump and the additive injection system comprises one or more foam pumps for injecting foam concentrate into a foam-mixing segment of the discharge system. An air compressor is also provided for injecting compressed air into an air mixing segment located downstream of the foam-mixing segment. The foam pumps are centrifugal pumps and the air compressor is a centrifugal compressor, all sharing a shaft with a hydraulic turbine or reverse centrifugal pump that is powered by the energy of the water flowing through the discharge line of the primary pump. Because of their common shaft, the hydraulic turbine, the foam pumps, and the air compressor all operate at the same speed. Thus, any increase or decrease in the volume of water flowing through the discharge system results in a results in a proportionate increase or decrease in the volume of foam concentrate and air injected into the system. No additional flow controls are needed. However, microprocessor-controlled valves may be provided in the foam and air conduits if extra precision is desired.
The foregoing and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments thereof taken in conjunction with the drawings in which:
Turning now to the drawings, attention is first directed to
The system 10 comprises a hydraulic motor or super-charger 12 positioned between the discharge line 14 of a fire engine pump (not shown) and a hose or set of hoses 16 for spraying water at a fire. A water control valve 13 is provided between the pump and the supercharger 12 for controlling the flow of water into the system. Each hose 16 includes a foam mixing segment 15 where the water from the fire engine pump can mix with different types of foam concentrates, such as, for instance, Class A foam concentrate suitable for fighting wildfires and structural fires, or Class B foam concentrate suitable for extinguishing flammable liquid fires. Downstream of the foam mixing segment 15 is an air mixing segment 17 where compressed air from an air compressor 18 is injected into the water-foam concentrate mixture, creating fully aerated foam. The system preferably also includes a flow meter 20 for measuring the amount of water induced into the system, and for displaying this information on a gauge 21 on the fire truck dashboard or elsewhere.
Separate foam delivery systems may be provided for each type of foam concentrate. For instance, Class A foam concentrate may be stored in a first foam tank 22 and pumped by a first foam pump 24 through a first foam conduit 26 leading to the foam-mixing segment 15. Similarly, Class B foam concentrate may be stored in a second foam tank 28 and pumped by a second foam pump 30 through a second foam conduit 32 leading to the foam-mixing segment 15. Furthermore, each foam conduit 26, 32 may be provided with a foam control valve 34, 36, respectively, for controlling the volume of concentrate delivered to the foam-mixing segment 15.
Similarly, an air control valve 38 may be provided for controlling the volume of air injected into the air mixing segment 17. In addition, the air compressor 18 is preferably provided with an air cleaner 40 for filtering smoke and the like out of the ambient air, so that it can be used to resuscitate victims of smoke-inhalation.
The hydraulic motor or super-charger 12 of the present invention consists of a hydraulic turbine or reverse centrifugal pump with contoured blades. It is powered by the energy of the water flowing through the discharge line 14 of the pump, and shares a drive shaft 39 with the air compressor 18 and foam pumps 24, 30. Thus, the rate of compressed air and foam concentrate flowing into the system is proportional to the flow rate of the water going through the pump, which in turn is proportional to the cross-sectional area of the hose or hoses 16 and the pressure of the pump and discharge nozzle 42. This eliminates the need for precise mixing controls of the type currently found on many fire vehicles.
In the simplest embodiment of the invention, no further controls are needed, since the amount of air and foam concentrate injected into the system is automatically regulated by the amount of water discharged by the pump. However, in the alternate embodiment shown in the control diagram of
In summary, the system operates as follows. When the water control valve 13 is open, water in the discharge line 14 of the pump flows into the hydraulic motor 12, exerting a force on the blades of the motor 12 and causing the drive shaft 39 to spin, in turn actuating both the air compressor 18 and the foam pumps 24 and 30. The water then flows into the foam-mixing segment 15 of the fire hose 16, where it mixes with foam concentrate from one or more of the foam tanks 22, 28. Next, it passes through a first mixing plate 44 where turbulence is induced, allowing mixing to take place most efficiently. Then, the water-foam concentrate mixture enters the air-mixing segment 17 where it mixes with compressed air from the air compressor 18. After passing through a second mixing plate 46 where turbulence is once again induced, the fully aerated foam is then discharged through the nozzle 42 at a rate determined by the firefighter.
Various modifications and variations to the embodiments herein chosen for purposes of illustration will readily occur to those skilled in the art. To the extent that such modifications and variations do not depart from the spirit of the invention, they are intended to be included within the scope of thereof.
