Abstract:
A mount for coupling a device to a support structure in a vehicle, the vehicle including a fuel tank for storing fuel, includes a canister having at least one surface insertable into the fuel tank so as to contact the fuel, the canister being impervious to the fuel. A cartridge is removably insertable into the canister, the cartridge being in thermal communication with the at least one surface, wherein the cartridge includes the device.

Description:
RELATED APPLICATION DATA  
       [0001]     This application claims priority of U.S. Provisional Application No. 60/706,176 filed on Aug. 5, 2005, and U.S. Provisional Application No. 60/709,348 filed on Aug. 18, 2005, both of which are incorporated herein by reference in their entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to liquid sensing arrangements and, more specifically, to utilizing thermal energy stored in fuel to maintain a temperature of an area or device.  
       BACKGROUND OF THE INVENTION  
       [0003]     On aircraft composed of carbon fiber composite wings, the length of wiring to sensors in wing-mounted fuel tanks is kept as short as possible. This minimizes the threat of a lightning strike conducting a significant quantity of energy into the fuel tank.  
         [0004]     To minimize wiring length in the fuel tanks, several fuel level sensors in one or more fuel tanks connect to a local data concentrator device. This device, which is sometimes referred to as a remote data acquisition unit (RDAU) or remote data concentrator (RDC) (hereinafter referred to as an electronics module), is usually mounted just outside of the fuel tank on a spar. The electronics module has a sealed connector that passes through the tank wall, making electrical connections to sensors inside the fuel tank. The electronics module includes active electronic devices (often including a microprocessor) that have temperature ratings typically extending down to about minus forty degrees Celsius.  
         [0005]     During flight, the temperature on a wing spar can fall as low as minus seventy degrees Celsius, which is significantly lower than the rating of many electronic devices. When an electronics module, such as the RDAU, is mounted on a spar of an aircraft&#39;s wing and connected to sensors within the wing&#39;s fuel tank, the electronics module is subjected to the low temperatures encountered during flight (e.g., as low as minus seventy degrees Celsius).  
         [0006]     One approach to addressing these low spar temperatures is to add a heating element to the electronics module. The addition of the heating element, however, adds cost and complexity to the electronics module. Another approach has been to test all vulnerable electronic components at the minimum operating temperature seen at the spar. Then, only those components that can satisfactorily operate at these temperatures are used in the electronics module. Often, however, only a very small number of components can pass the test, resulting in low yields and, thus, increased costs.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides a system, apparatus and method for maintaining an ambient temperature for a device located within a vehicle, in particular an aircraft. More specifically, thermal energy stored within the vehicle&#39;s fuel is utilized to maintain the ambient temperature within safe operating regions of the device.  
         [0008]     According to one aspect of the invention, there is provided a mount for coupling a device to a support structure in a vehicle, the vehicle including a fuel tank for storing fuel. The mount device includes a canister having at least one surface exposed to an inner portion of the fuel tank, the canister being impervious to the fuel. A cartridge is located inside the canister, the cartridge being in thermal communication with the at least one surface, wherein the cartridge includes the device.  
         [0009]     According to another aspect of the invention, there is provided a system for maintaining an ambient temperature of an area within an operational range of one or more devices located in the area. The system includes a fuel tank for storing fuel, and a heat exchanger operative to extract thermal energy from fuel stored in the fuel tank.  
         [0010]     According to another aspect of the invention, there is provided a method of mounting a device in a vehicle so as to maintain an ambient temperature around the device within an operation range of the device. The method includes the steps of: placing at least one surface of a canister in fluid communication with the fuel, wherein said canister is impervious to said fuel; placing a cartridge inside the canister such that the cartridge is in thermal communication with the fuel; and placing the device inside the cartridge.  
         [0011]     According to another aspect of the invention, there is provided a method of maintaining an ambient temperature for a device in a vehicle, including using thermal energy of fuel stored in the vehicle to heat or cool the device.  
         [0012]     According to another aspect of the invention, there is provided a mount for maintaining an ambient temperature of an area within an operational range of one or more devices located in the area. The mount includes a receptacle (e.g., a container or the like) extending into an interior of a fuel tank and opening to an exterior of the fuel tank, a sealed connector for establishing a through connection from the interior of the fuel tank to the interior of the receptacle, and a cartridge assembly insertable into the receptacle.  
         [0013]     To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative, however, of but a few of the various ways in which the principles of the invention may be employed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The forgoing and other embodiments of the invention are hereinafter discussed with reference to the drawings.  
         [0015]      FIG. 1  is an exemplary aircraft showing the location of fuel tanks and fuel sensors.  
         [0016]      FIGS. 2A and 2B  are a front view and side view, respectively, of an exemplary canister of a mounting system in accordance with the invention.  
         [0017]      FIG. 3  is a side view of an exemplary cartridge in accordance with the invention, wherein an exemplary electronics module is shown inside the cartridge.  
         [0018]      FIG. 4  is a side view illustrating the canister, cartridge and electronics module mounted to a wing spar in accordance with the invention.  
         [0019]      FIG. 5  is a schematic diagram illustrating an exemplary power source for the electronics module. 
     
    
     DETAILED DESCRIPTION  
       [0020]     Referring initially to  FIG. 1 , an exemplary aircraft  10  includes a plurality of fuel tanks  12  mounted in wings  14  or other locations in the aircraft (not shown). Each fuel tank  12  includes one or more fuel sensors  16  for monitoring a fuel parameter, such as the fuel level or fuel temperature, for example. An electronics module  18  is mounted to a spar (not shown), and communicates to the fuel sensors  16  and other equipment. During flight, the wings  14  and spars within the wings  14  are exposed to extreme temperatures (e.g., about minus seventy degrees Celsius), which can be problematic for the fuel sensor&#39;s electronics module  18 .  
         [0021]     The present invention provides a system, apparatus and method for maintaining an ambient temperature for a device, such as the fuel sensor&#39;s electronics module  18 , so as to shield or isolate the module  18  from the extreme temperatures encountered during flight or while on the ground. Moreover, active heating elements or special testing of the electronics module&#39;s components are not required (although such devices and/or techniques may be utilized within the scope of the invention). As described herein, thermal energy of fuel stored in the vehicle is used to maintain the ambient temperature for the device such that it is substantially the same as the fuel (e.g., within about five to ten degrees Celsius).  
         [0022]     While the invention is described with respect to maintaining an ambient temperature for an electronics module, it will be appreciated that the invention may be used to maintain the ambient temperature for any device (electronic and non-electronic) or area. Further, while the invention is described in the context of an aircraft, it will be appreciated that it may be employed on any vehicle that utilizes relatively large fuel tanks, such as ships and locomotives, for example.  
         [0023]     According to one aspect of the invention, a canister is in contact with the aircraft fuel and impervious to the fuel. The canister operates as a heat exchanger and utilizes the thermal energy stored in the fuel to maintain an ambient temperature within the canister. As will be appreciated, other types of heat exchangers may be used in place of the canister without departing from the scope of the invention (e.g., a shell and tube heat exchanger, a plate heat exchanger, etc.).  
         [0024]     A cartridge is located within the canister, and the electronics module  18  is located in or on the cartridge. Both enclosures (i.e., the canister and cartridge) include sealed connectors that enable signals to enter and/or exit the respective enclosures while preventing fuel from entering the enclosures. By utilizing two enclosures, the thermal energy of the fuel can be easily used to maintain the temperature within both enclosures (and thus the electronics module  18 ), yet allow easy removal of the electronics module  18  without concern of fuel leakage or spillage.  
         [0025]     As used herein, a canister is defined as a container, such as a box, can, cylinder, or the like. A cartridge is defined as a small modular unit designed to be inserted into a larger piece of equipment, such as a canister.  
         [0026]     Referring now to  FIGS. 2A and 2B , there is shown a front and side view of an exemplary canister  20  mounted to a wing spar  22  of aircraft  10 . As is conventional, the wing spar  22  defines a portion of a fuel tank  12  for holding fuel  24 . At least a portion of the canister  20  is in contact with the fuel  24 . Preferably, the canister  20  is located near a lower portion of the tank  12  so as to maintain contact with the fuel  24  for as long as possible as the fuel is consumed. Although the canister  20  is shown as a separate unit from the fuel tank  12 , the canister may be integrally formed with the fuel tank.  
         [0027]     The canister  20  comprises a cylindrical container having a diameter D and defined by circular bottom wall  20   a  and cylindrical side wall  20   b,  which also holds the canister  20  to the spar  22 . The canister includes a flange  20   d  for interfacing with the spar  22  and is secured to the spare via fasteners  26  (e.g., screws or the like). A cover  20   c  may be attached to the open end  20   e  of the canister. The canister  20  may be made out of any material that is impervious to the fuel. Preferably, the canister  20  is formed from a light-weight material, such as aluminum, for example. Additionally, an insulation means may be included between the canister  20  and the spar  22  for galvanic or other reasons.  
         [0028]     The cover  20   c  includes an opening  20   f  that enables access into the canister  20 . The flange  20   d  and/or cover  20   f  provide a means of accepting fasteners  28 , which secure the cartridge  40  when mounted in the canister  20 .  
         [0029]     The bottom wall  20   a  includes a hermetically sealed connector  30 , such as, for example, an electrical connector or fiber optic connector for communicating signals into and out of the canister  20 . For example, electrical or optical signals from fuel sensor  16  located within the fuel tank  12  can be provided to the interior of the canister  20  through the connector  30 , without fuel entering the canister  20 .  
         [0030]     Referring now to  FIG. 3 , there is shown an exemplary cartridge  40 . The cartridge  40  is defined by circular top and bottom walls  40   a  and  40   b,  and cylindrical sidewall  40   c.  The cartridge  40  is dimensioned so as to fit within the canister  20 . As will be appreciated, the cylindrical shape of the canister  20  and cartridge  40  is merely exemplary, and any shape may be utilized for the canister  20  and cartridge  40 . For example, the canister  20  may have a cylindrical shape and the cartridge  40  may have a rectangular shape, so long as the cartridge  40  fits within the canister  20 .  
         [0031]     Located within the cartridge  40  is an electronics module  18 . The electronics model  18  includes circuitry for performing conventional data acquisition and processing operations. For example, the electronics module  18  may include a number of integrated circuits, resistors, capacitors, etc. mounted on a printed circuit board and operative to exchange data between the fuel sensors  16  and a central controller (not shown) and/or to perform signal conditioning operations (e.g., signal filtering or the like). The electronics module  18  can be mounted to the top, bottom and/or sidewalls  40   a,    40   b  or  40   c  of the cartridge  40  using one or more mounting members  44 , such as fasteners and standoffs, for example.  
         [0032]     It is noted that the cartridge  40  may take on may different forms. For example, and as described above, the cartridge  40  may be a container wherein the electronics module  18  is mounted inside or on cartridge. Alternatively, the cartridge  40  may be a film, coating, or the like surrounding and/or formed over the electronics module  18  (e.g., the electronics module may be encased in an epoxy resin, or a thin coating may be formed over the outer surface of the electronics module  18 ). In another embodiment, the device itself may be the cartridge.  
         [0033]     The cartridge  40  also includes a first connector  46  and a second connector  48 . The first and second connectors  46  and  48  preferably are hermetically sealed connectors. This is advantageous, for example, in that if the connector  30  of the canister fails (e.g., it leaks), the fuel  24  will not be able to enter the interior of the cartridge  40  and contact the electronics module  18 . The first and second connectors  46  and  48  are couplable to the electronics module  18  so as to enable signals in/on the electronics module to be provided to other local or remote devices. For example, the first and second connectors  46  and  48  may be edge connectors that mate with corresponding edge portions of the electronics module&#39;s printed circuit board so as to provide an electrical connection to/from the electronics module  18 . As will be appreciated, any type of connecting means that enables signals to be transferred to/from the electronics module  18  and the canister  20  and cartridge  40  may be used.  
         [0034]     Further, the first connector  46  is couplable to the connector  30  of the canister  20 , thereby enabling signals to be transmitted and received from devices external to the canister  20  and cartridge  40 . For example, the connector  30  of the canister  20  may include a female receptacle (e.g., a fitting equipped to receive a plug or the like for facilitating an electrical connection), and the first connector  46  of the cartridge  40  may include a male plug that corresponds to the female receptacle. When the connectors  30  and  46  are coupled together, a connection (e.g. an electrical or optical connection) is made from the inside of the cartridge  40  to the outside of the canister  20  (e.g., from the electronics module  18  to the fuel sensors  16  located within the fuel tank  12 ).  
         [0035]     The second connector  48  extends through the top wall  40   c  of the cartridge  40  and is coupled to a wiring harness or the like, which is couplable to the central controller. Via the second connector  48 , signals may be transmitted to and/or received from devices located outside the canister  20  and cartridge  40 . For example, data collected by the electronics module  18  may be communicated to an avionics control system (not shown) or the like. Similarly, data may be communicated from the avionics control system to the electronics module  18  and/or the fuel sensors  12 . Such data may be in the form of feedback signals (e.g., actual fuel temperature, level, etc.) or command signals (e.g., alarm setpoints).  
         [0036]     With further reference to  FIG. 4 , the electronics module  18  and cartridge  40  are shown mounted in the canister  20 . As described above, the first connector  46  of the cartridge  40  mates with the connector  30  of the canister  20 . This connection provides a communication path from the electronics module  18  (which is inside the cartridge  40 ) to the fuel sensors  16  (which are in the fuel tank  12  outside of the canister  20 ). The cartridge  40  may be removed from and inserted into the canister  20  via opening  20  within the flange  20   d  and cover  20   c  (if present).  
         [0037]     As noted herein, the canister  20  is mounted near a bottom portion of the fuel tank  12  so as to immerse the canister  20  in fuel as long as possible. As the fuel is consumed, portions of the canister may become exposed and, as a result, the temperature of the canister  20  (and thus the cartridge  40  and electronics module  18 ) may approach that of the spar  22  and wing  14 . To slow this process (and keep the electronics module  18  from becoming too cold too quickly) thermal insulation  50  can be placed between the canister  20  and the spar  22  as show in  FIG. 4 . Preferably, the thermal insulation  50  is electrically conductive so as provide protection against lighting strikes. Additionally, it is noted that if the canister  20  is mounted near a bottom portion of the fuel tank  12 , exposure of the canister (if at all) occurs when the flight is nearly complete. Thus, the temperatures encountered by the exposed canister  20  will be substantially higher than minus 70 degrees Celsius.  
         [0038]     As is known by those skilled in the art, lightning strikes can pose problems for aircraft electronics. To minimize the effects of lightning strikes, the electronics module  18  can be electrically isolated from the aircraft&#39;s frame ground, thereby providing enhanced protection against such strikes. For example, the electronics module  18  can be powered by an isolated power source. More specifically, and with reference to  FIG. 5 , a high frequency AC power source  52  can be used to power the electronics module  18 . Preferably, the power source  52  operates on a frequency in the region of 10 KHz. The high frequency power source  52  is advantageous, for example, in that it allows the electronics module&#39;s power supply  18   a  to remain electrically isolated from other aircraft electronics. The electrical isolation can be accomplished, for example, using a small, lightweight ferrite transformer  52   a  in or near the power source  52 . Additionally, by utilizing the high frequency power source  52 , the power requirements of the electronics module  18  are simplified, thereby reducing the size and weight of the electronics module  18 . The ferrite transformer  42   a  is designed to provide intrinsic safety, and forms part of the intrinsic safety barrier. Intrinsic safety of digital signals can be provided by optical isolation  52   b.  The electronics that interface with the in-tank sensors through connectors  46  and  30  are thus completely electrically isolated. Note that direct current power can be used, but additional circuitry would be required to provide the high frequency excitation for the ferrite transformer  52   a.    
         [0039]     Accordingly, an ambient temperature can be maintained for a device, such as an electronics module, using thermal energy stored in fuel. The thermal energy may be extracted via a mounting system that includes at least two enclosures, wherein one of the enclosures is in contact with the fuel and the other enclosure is in thermal communication with the fuel. As will be appreciated, other techniques of extracting the thermal energy from the fuel may be employed without departing from the scope of the invention.  
         [0040]     Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described elements (components, assemblies, devices, compositions, etc.), the terms (including a reference to a “means”) used to describe such elements are intended to correspond, unless otherwise indicated, to any element which performs the specified function of the described element (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiment or embodiments of the invention. In addition, while a particular feature of the invention may have been described above with respect to only one or more of several illustrated embodiments, such feature may be combined with one or more other features of the other embodiments, as may be desired and advantageous for any given or particular application.