Patent Document

FIELD OF THE INVENTION  
       [0001]     This invention relates to systems and methods for fluid level detection, and more specifically, to systems and methods for measuring fuel levels within fuel tanks using optical fibers.  
       BACKGROUND OF THE INVENTION  
       [0002]     Many types of vehicles and machines consume fuel during operation, including aircraft, ships, construction vehicles, and a wide variety of other machinery. As vehicles and machines operate, the level of fuel within a fuel tank decreases. As fuel is added, the fuel level increases. A variety of systems and methods are known to provide an indication of the amount of fuel within the fuel tank, including, for example, those systems disclosed in U.S. Pat. No. 6,571,626 B1 issued to Herford, U.S. Pat. No. 6,408,692 B1 issued to Glahn, and U.S. Pat. No. 4,627,283 issued to Nishida et al. Although desirable results have been achieved using such prior art systems, there is room for improvement.  
       SUMMARY OF THE INVENTION  
       [0003]     The present invention is directed to systems and methods for sensing fluid levels using optical fibers, including measuring fuel levels within fuel tanks, and transmitting this data through optical fibers. Embodiments of systems and methods in accordance with the present invention may advantageously allow fluid levels within a tank to be determined without the need to transmit electrical signals into the tank, and may also improve the costs associated with maintenance and repair of fluid level sensors in comparison with the prior art.  
         [0004]     In one embodiment, a sensor assembly adapted to sense a fluid level includes at least one optical fiber adapted to at least one of transmit and receive an optical signal, and a moveable float member. The float member is adapted to move in a first direction as the fluid level increases and in a second direction as the fluid level decreases. The float member blocks the optical signal at a first value of the fluid level, and allows the optical signal to pass at a second value of the fluid level. The presence or absence of the optical signal is detected to determine the level of fluid. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0005]     Preferred and alternate embodiments of the present invention are described in detail below with reference to the following drawings.  
         [0006]      FIG. 1  is a side elevational view of a fuel tank assembly in accordance with an embodiment of the invention;  
         [0007]      FIG. 2  is an enlarged, side elevational view of a sensor assembly of the fuel tank assembly of  FIG. 1  in accordance with an embodiment of the invention;  
         [0008]      FIG. 3  is a flow diagram of a method of sensing a fuel level in accordance with a further embodiment of the invention;  
         [0009]      FIG. 4  is a side elevational view of an aircraft in accordance with yet another embodiment of the invention;  
         [0010]      FIG. 5  is a side elevational view of a sensor assembly in accordance with an alternate embodiment of the invention;  
         [0011]      FIG. 6  is a side elevational view of a sensor assembly in accordance with another alternate embodiment of the invention; and  
         [0012]      FIG. 7  is a side elevational view of a sensor assembly in accordance with a further embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0013]     The present invention relates to systems and methods for measuring fuel levels within fuel tanks using fiber optics. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1-7  to provide a thorough understanding of such embodiments. The present invention may have additional embodiments, or may be practiced without one or more of the details described for any particular described embodiment.  
         [0014]      FIG. 1  is a side elevational view of a fuel tank assembly  100  in accordance with an embodiment of the invention. In this embodiment, the fuel tank assembly  100  includes a tank  102  and a sensor assembly  110  coupled to the tank  102  by a support  104 .  FIG. 2  is an enlarged, side elevational view of the sensor assembly  110  of  FIG. 1 . In this embodiment, the sensor assembly  110  includes an optical sensor  112  coupled by first and second optical fibers  114 ,  116  to a converter switch  120 . The converter switch  120  may be a conventional component, including, for example, those converter switches commercially available. The first and second optical fibers  114 ,  116  pass through a sealing member  118  disposed within the wall of the fuel tank  102 . A power source  122  is coupled to the converter switch  120 .  
         [0015]     As further shown in  FIG. 2 , the optical sensor  112  includes a float  124  disposed within a guide member  126  adapted to partially limit a range of motion of the float  124 . The first optical fiber  114  is coupled to an upper portion of the guide member  126 , and the second optical fiber  116  is coupled to the guide member  126  opposite from the first optical fiber  114 . An end portion of the first optical fiber  114  thus forms an emitter  128 , and an opposing end portion of the second optical fiber  116  forms a receiver  130 .  
         [0016]     Referring again to  FIG. 1 , the converter switch  120  may be coupled to a processor (or CPU)  132  which, in turn, may be coupled to a display device  134  (e.g. a gauge, digital readout, display, etc.), and to a pump  136 . A first conduit  138  is coupled between a fuel source (not shown) and the pump  136 , and a second conduit  140  is coupled between the pump  136  and the tank  102 .  
         [0017]     In operation, power is provided by the power source  122  along an input lead  121  to the converter switch  120 . The converter switch  120  outputs and optical signal along the first optical fiber  114 . The optical signal may be composed of visible or non-visible light (ultraviolet or infrared), may be monochromatic or non-monochromatic, and may be continuous or non-continuous. As best shown in  FIG. 2 , at a first fuel level  142 , the float  124  is positioned at a lower position  144  in which the float  124  is not disposed between the emitter  128  and the receiver  130 , allowing the optical signal to transmit the between the emitter  128  and the receiver  130 . The optical signal then passes along the second optical fiber  116  to the converter switch  120 . A corresponding output signal may be transmitted along an output lead  123  to the processor  132 . The processor  132  may interpret the output signal and may provide an indication of the fuel level within the fuel tank  102  to the display  134 .  
         [0018]     The processor  132  may also provide a control signal to the pump  136 , including, for example, a first control signal that causes the pump  136  to pump additional fuel from the fuel source (not shown) into the fuel tank  102 . As the fuel level within the tank  102  rises and approaches an upper fuel level  148  ( FIG. 1 ), the float  124  is raised to a second position  146  in which it is disposed between the emitter  128  and the receiver  130  thereby blocking the optical signal. As the optical signal is no longer received at the converter switch  120 , the output signal may cease to be transmitted along the output lead  123  to the processor  132 . In response, the processor may transmit a second control signal that causes the pump  136  to stop pumping.  
         [0019]      FIG. 3  is a flow diagram of a method  300  of sensing a fuel level in the tank  102  in accordance with one embodiment of the invention. In this embodiment, the method  300  includes transmitting the optical signal from the converter switch  120  along the first optical fiber  114  at a block  302 . At a block  304 , a determination is made regarding whether the optical signal is being received at the receiver  130 . If the optical signal is being received, then at a block  306 , appropriate action is taken to operate the pump  136  to raise the fuel level within the tank  102 , and the method  300  returns to the determination block  304 . Alternately, if the optical signal is not been received, then appropriate action is taken to stop the pump  136  at block  308 , and again, the method  300  returns to the determination block  304 . The method  300  may continue indefinitely, or may be terminated at any desired time.  
         [0020]     Embodiments of the present invention may provide significant advantages over the prior art. For example, because the sensor assembly  110  utilizes an optical signal rather than an electrical signal, there is no need for an electrical signal to be transmitted within the tank  102 , thereby improving the safety of the assembly. Furthermore, the simplicity of the sensor assembly  110  may increase reliability and reduce the costs associated with maintenance and repair.  
         [0021]     Embodiments of the present invention may be used in a wide variety of applications, including aircraft, ships, construction vehicles, and a wide variety of other machinery. For example,  FIG. 4  is a side elevational view of an aircraft  400  in accordance with yet another embodiment of the invention. The aircraft  400  generally includes a variety of components and subsystems generally known in the pertinent art, and which, in the interest of brevity, will not be described in detail. For example, the aircraft  400  generally includes one or more propulsion units  402  that are coupled to wing assemblies  404 , or alternately, may be coupled to a fuselage  406  or even other portions of the aircraft  400 . Additionally, the aircraft  400  includes a tail assembly  408  and a landing assembly  410  coupled to the fuselage  406 , and a flight control system  412  (not shown in  FIG. 4 ), as well as a plurality of other electrical and mechanical systems and subsystems that cooperatively perform a variety of tasks necessary for the operation of the aircraft  400 . The aircraft  400  also includes one or more fuel tank assemblies  414  (not visible) in accordance with the present invention. The fuel tank assemblies  414  may be disposed within the wing assemblies  404  and within the fuselage  406  of the aircraft  400 .  
         [0022]     The aircraft  400  shown in  FIG. 4  is generally representative of a commercial passenger aircraft, including, for example, the  737 ,  747 ,  757 ,  767  and  777  commercial passenger aircraft available from The Boeing Company of Chicago, Ill. In alternate embodiments, however, embodiments of the invention may be incorporated into flight vehicles of other types. Examples of such flight vehicles include other commercial aircraft, manned or unmanned military aircraft, rotary wing aircraft, or types of flight vehicles, as illustrated more fully in various descriptive volumes, such as Jane&#39;s All The World&#39;s Aircraft, available from Jane&#39;s Information Group, Ltd. of Coulsdon, Surrey, UK.  
         [0023]     It will be appreciated that a variety of alternate embodiments of sensor assemblies in accordance with the present invention may be conceived, and that the invention is not limited to the particular embodiments described above. For example,  FIG. 5  is a side elevational view of a sensor assembly  500  in accordance with an alternate embodiment of the invention. In this embodiment, the sensor assembly  500  includes a float  502  having an opaque portion  504  and an optically-transmissive portion  506 . In operation, when the fuel level within the fuel tank  102  approaches the upper fuel level  148  ( FIG. 1 ), the optically-transmissive portion  506  of the float  502  is disposed between the first and second optical fibers  114 ,  116 , allowing the optical signal  508  to pass therebetween. As the fuel level within the tank  102  drops, the float  502  moves in a downward direction  510  until the opaque portion  504  of the float  502  is disposed between the first and second optical fibers  114 ,  116 , blocking the optical signal  508 . The sensor assembly  500  may be suitably coupled to one or more other components to perform other desired functions, including, for example, to monitor or maintain a desired fuel level within the fuel tank  102 . More specifically, with reference to  FIG. 1 , the sensor assembly  500  may be coupled to the converter switch  120  which may, in turn, transmit an electrical signal to the processor  136  when the fuel level is at or near the upper fuel level  148 . As the fuel level decreases and the opaque portion  504  blocks the optical signal  508 , the converter switch  120  may cease transmitting the electrical signal to the processor  136 , which may in turn transmit a control signal to the pump  136  to cause additional fuel to be supplied to the tank  102 .  
         [0024]      FIG. 6  is a side elevational view of a sensor assembly  600  in accordance with another alternate embodiment of the invention. In this embodiment, a single optical fiber  602  is directed toward a reflective surface  604 . In operation, an optical signal  606  emitted by the optical fiber  602  is transmitted toward the reflective surface  604 , and a reflected signal  608  is transmitted back from the reflective surface  604  to the optical fiber  602 . As a fuel level within the fuel tank  102  rises, an opaque float  610  moves in an upward direction  612  until it blocks at least one of the optical signal  606  and the reflected signal  608 . The sensor assembly  600  may be suitably coupled to one or more other components to perform other desired functions, including, for example, to monitor or maintain a desired fuel level within the fuel tank  102 . More specifically, the sensor assembly  600  may be coupled to the converter switch  120  ( FIG. 1 ). As the reflected signal  608  is received by the single optical fiber  602 , it may be transmitted back to the converter switch  120  which may, in turn, transmit an electrical signal to the processor  136 , indicating that the fuel level is not at or near the upper fuel level  148 . The processor  136  may, in turn, cause the pump  136  to provide additional fuel to the fuel tank  102 . As the fuel level increases and the opaque float  610  blocks at least one of the optical signal  606  and the reflected signal  608 , the converter switch  120  may cease transmitting the electrical signal to the processor  136 , which may in turn cause the pump  136  to cease.  
         [0025]      FIG. 7  is a side elevational view of a sensor assembly  700  in accordance with a further embodiment of the invention. In this embodiment, the sensor assembly  700  includes a plurality of transmitting fibers  702 , a plurality of receiving fibers  704 , and an opaque float  706 . In operation, an optical signal  708  transmitted from each of the transmitting fibers  702  is either received by a corresponding receiving fiber  704 , or blocked by the opaque float  706 . As a fuel level within the fuel tank  102  rises, the opaque float  706  moves in an upward direction  710 , blocking an increasing number of the optical signals  708 .  
         [0026]     The sensor assembly  700  may be suitably coupled to one or more other components to perform other desired functions, including, for example, to monitor or maintain a desired fuel level within the fuel tank  102 . More specifically, the sensor assembly  700  may be coupled to one or more converter switches  120  ( FIG. 1 ) which may, in turn, be coupled to the processor  132 . Based on the number of optical signals  708  blocked by the opaque float  706 , the processor  132  may determine the fuel level within the fuel tank  102 , and they send appropriate control signals to raise the level as desired.  
         [0027]     As mentioned above, embodiments the present invention may be used in a wide variety of applications, including aircraft, ships, construction vehicles, and a wide variety of other machinery. It will be appreciated that embodiments of the present invention may also be used to monitor the level of fluids other than fuel, including other flammable liquids (e.g. liquid propane, oil, etc.), or nonflammable liquids (e.g. water, juice, milk, etc.). Therefore, although embodiments of the present invention had been described above with respect to the measurement of fuel within a fuel tank, it will be appreciated that embodiments of the present invention may be used in a wide variety of applications that do not involve the measurement of fuel.  
         [0028]     While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.

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