Compressed air foam is used to extinguish fires and is generally comprised of a combination of water and a foam concentrate solution mixed together to form an agent mixture. The agent mixture is then subjected to compressed air so as to create a foam mixture for delivery to a fire. Depending on characteristics of the fire (e.g., related to size, fuel source, environmental factors) different agent mixture ratios and/or flow rates are selected to extinguish the fire. Current air foam delivery systems are managed manually by an operator so as to achieve the desired agent mixture ratio and flow rate depending on variables of the system.
A compressed air foam delivery system includes a control unit to dynamically monitor and/or adjust components within the system so as to deliver a compressed air foam agent mixture with a desired agent:air ratio at a desired flow rate to one or more active discharges. In one embodiment, the control unit can be equipped to control one or more of a pump engine, water pump, foam delivery unit and air compressor so as to deliver and maintain the desired ratio of agent mixture at the desired flow rate.
In one embodiment, system 10 is supported by a fire truck and can be configured to draw mechanical and/or electrical power from the fire truck. System 10 includes a control unit 12 operable to dynamically control components within the system 10 in order to deliver a foam mixture having a desired agent:air ratio (i.e., at a desired proportion of agent mixture to air) at a desired flow rate. In particular, control unit 12 is operably coupled to a pump engine 14, a water pump 16, a solution delivery unit 18 and an air compressor 20. Through control of these components, control unit 12 delivers a desired foam mixture at a desired flow rate to one or more discharges 22, 24 and 26. Although three discharges 22, 24 and 26 are herein illustrated, more or less discharges may be utilized in delivering a foam mixture.
In one embodiment, control unit 12 monitors and adjusts at least one of the following variables in delivering a foam mixture to one or more of the discharges 22, 24 and 26: revolutions per minute of pump engine 14, water pressure within water pump 16, water flow rate within water pump 16, solution injection percentage delivered by solution delivery unit 18, air pressure within air compressor 20, and air flow rate within air compressor 20. Additionally, control unit 12 monitors one or more of the agent:air ratio and the flow rate of foam mixture delivered to the discharges 22, 24 and 26. The monitoring of ratio and flow rate at the discharges 22, 24, 26 provides feedback to control unit 12 such that components controlled by the control unit 12 can be adjusted in order to deliver the desired ratio and flow rate of foam mixture to active discharges 22, 24, 26. To this end, a situation may arise where one or more of the discharges is active and one or more of the discharges is inactive. Circumstances may dictate that one of the inactive discharges be activated (i.e., brought online) so as to actively deliver foam mixture. Having an additional active discharge (or shutting down an active discharge) alters characteristics within system 10 such that control unit 12 can dynamically adjust components within the system 10 such that each active discharge delivers the desired ratio and flow rate of foam mixture.
In order to deliver the foam mixture to active discharges, pump engine 14 operates to provide power to the water pump 16, which can be connected to a suitable water source (not shown). Example water sources include a tank on the fire truck, a draft source such as a pond or lake coupled to an intake of the fire truck and a pressurized source such as a fire hydrant. In one embodiment, control unit 12 is operably coupled to one or more intake valves that connect pump 16 with a water source. Pump engine 14, in one embodiment, is a separate combustion engine that operates at a particular revolutions per minute (RPM) setting that is controllable by the control unit 12. In another embodiment, the pump engine 14 can be a main engine for the fire truck, where the pump 16 is coupleable to the main engine through a power take off assembly. In any event, control unit 12 is configured to increase or decrease the RPM setting of the pump engine 14 in order to achieve a desired ratio and flow rate of foam mixture.
In one embodiment, control unit 12 is further coupled to a priming system 27 capable of priming pump 16. In particular, the priming system 27 can include a pump to replace air within pump 16 with water. In a further embodiment, the priming system 27 can include a pressure sensor to indicate when the pump 16 is primed. Once pump 16 is primed, control unit 12 can operate to turn off priming system 27. In any event, the control unit 12 is configured to prime and operate pump 16 prior to implementation and operation of the solution delivery unit 18 and/or the air compressor 20. In particular, the control unit 12 can detect a pressure in the water pump 16. If no or low pressure is detected, the priming system 27 is activated by the control unit 12 to prime pump 16. Once control unit 12 detects pump 16 is primed by detecting a particular pressure level, the solution delivery unit 18 and air compressor 20 can be operated to deliver a foam mixture.
Upon operation of the pump engine 14, water pump 16 operates to deliver water to a solution mixing chamber 28. Within solution mixing chamber 28, solution delivery unit 18 operates to inject concentrate solution into the water supplied by the water pump 16 in a proportion so as to form a water/solution mixture, also referred to herein as an agent mixture. To this end, the solution delivery unit 18 can include a pump coupled to chamber 28 to deliver solution thereto. In one embodiment, the percentage of solution introduced into the water can be in a range of approximately 0.3%-6.0%. Control unit 12 is operable to control solution delivery unit 18 so as to adjust the percentage of solution delivered to the solution mixing chamber 28 in order to produce an agent mixture with a desired water to solution proportion. In one embodiment, production of the agent mixture can be performed in a manner similar to that disclosed in U.S. Patent Application Publication No. 2008/0035201, herein incorporated by reference. For example, a conductivity of water supplied to the chamber 28 can be compared with a conductivity of the agent mixture exiting chamber 28. These conductivity readings can be supplied to control unit 12 in order to provide a desired water to solution ratio for the agent mixure.
From solution mixing chamber 28, the agent mixture travels to an air mixing chamber 30, where compressed air from the air compressor 20 is introduced into the agent mixture to create a foam mixture. Controller 12 is operable to adjust the air compressor 20, in particular with regards to a signal indicative of an air pressure setting and/or an air flow setting within the air compressor 20. Once air is introduced to the agent mixture within the air mixing chamber 30, the foam mixture can be discharged through the one or more discharges 22, 24 and 26. Each of the discharges 22, 24, and 26 can be equipped with a flow sensor and/or a conductuity sensor (generally indicated as respective sensor assemblies 32, 34, 36) that can measure the flow rate and ratio of the foam mixture that is discharged from air mixing chamber 30. Based on the readings from these sensor assemblies 32, 34, 36, control unit 12 can adjust one or more settings of the pump engine 14, water pump 16, solution delivery unit 18 and air compressor 20 in order to achieve the desired mixture ratio and flow rate at each active discharge.
Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes can be made in form and detail without departing from the spirit and scope of the present invention.
This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/558,556 filed on Nov. 11, 2011, and incorporated herein by reference.
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