Abstract:
A fluid control system may comprise a pressurized fluid path; at least two sensors for determining a state of fluid within the main fluid path; an isolation valve; and fluid-filled connection paths between the main fluid path and each of the at least two sensors. The connection paths may comprise first sensing tubes connected between the main fluid path and the isolation valve; the isolation valve; and second sensing tubes connected between the isolation valve and the at least two sensors. Upon closure of the isolation valve, the connection paths may be interrupted so that the sensors may be isolated from the main fluid path and so that they may be removed from the system without a need to de-pressurize or drain the fluid from the main fluid path of the system.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention generally relates to fluid control systems which employ sensors for determining a state of fluids in the system and more particularly to such systems in which ease of maintenance is provided. 
         [0002]    In some fluid control systems, a pump may be employed to pressurize fluid which is then driven through a closed-loop path to activity points of the system. For example, a hydraulic control system may use pressurized fluid to activate cylinders or hydraulic motors. Or, a cooling system may use pressurized cooling fluid to transfer heat to or from various sources of heat. During operation of such fluid control systems, it may be desirable to determine the pressure and/or temperature of the fluid at various locations within the system. Pressure sensors and/or temperature sensors may be employed to continuously measure these parameters. 
         [0003]    Fluid control systems are often incorporated into vehicles such as aircraft. Aircraft fluid control systems may require routine maintenance to assure continued safe operability. The pressure and/or temperature sensors of these fluid control systems may need to be repaired or replaced during maintenance. Sensor replacement requires opening of the closed-loop fluid system and removal of the fluid from the system. Many fluid control systems contain a substantial quantity of expensive specialized fluid. Efforts associated with draining and re-filling the fluid control system and possible loss of the fluid contribute to high maintenance costs of vehicles such as aircraft. 
         [0004]    In some aircraft, the sensors may be located in various positions in the aircraft which may not be readily accessible for routine maintenance. Gaining access to sensors for maintenance purposes may also contribute to high maintenance costs. 
         [0005]    As can be seen, there is a need to provide fluid control systems in which replacing and/or repairing of sensors may be performed without a need to drain and refill, or de-pressurize the fluid control system. Furthermore there is a need to provide such fluid control system wherein the sensors may be readily accessible for maintenance purposes. 
       SUMMARY OF THE INVENTION 
       [0006]    In one aspect of the present invention, a fluid control system may comprise a main fluid path; at least two sensors for determining a state of fluid within the main fluid path; an isolation valve; and fluid-filled connection paths between the main fluid path and each of the at least two sensors. The connection paths may comprise first sensing tubes connected between the main fluid path and the isolation valve; the isolation valve; and second sensing tubes connected between the isolation valve and the at least two sensors. Upon closure of the isolation valve, the connection paths may be interrupted so that the sensors may be isolated from the main fluid path. 
         [0007]    In another aspect of the present invention, a sensor isolation system for a fluid control system may comprise an isolation valve which may comprise at least one cylinder with a closed end having an inlet and an outlet port formed through the closed end; at least one piston movably positionable within the at least one cylinder so that the inlet and outlet ports are open when the piston is in a first position and so that a free end of the at least one piston occludes the inlet and outlet ports when the piston is in a second position; a first pressure sensing tube connecting a main fluid path of the fluid control system with the inlet port; and a second pressure sensing tube connecting the outlet port to a fluid-state sensor. Movement of the piston into its second position may isolate the sensor from the main fluid path. 
         [0008]    In a further aspect of the present invention, a method for a method of removing a sensor from a fluid control system without draining fluid from the system may comprise the steps of: providing at least two sensors to determine a state of fluid in a main fluid path of the system; providing fluid-filled connection paths between the main fluid path and each of the at least two sensors wherein the connection paths include an isolation valve; closing the isolation valve to interrupt the connection paths so that the sensors are isolated from the main fluid path when removal of any one or more of the sensors is required for repair or replacement; and removing one or more of the sensors. The removing step may be performed without draining fluid from the main fluid path. 
         [0009]    These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic block diagram of a fluid control system in accordance with an embodiment of the present invention; 
           [0011]      FIG. 2  is a partial cross-sectional view of an isolation valve in accordance with an embodiment of the present invention; 
           [0012]      FIG. 2A  is a partial cross-sectional view of the isolation valve of  FIG. 2  in accordance with an embodiment of the present invention; 
           [0013]      FIG. 2B  is a partial elevation view of the isolation valve of  FIG. 2  in accordance with an embodiment of the present invention; 
           [0014]      FIG. 2C  is an enlarged view of a portion of the isolation valve of  FIG. 2  in accordance with an embodiment of the present invention; 
           [0015]      FIG. 3  is a first perspective view of driving member of the isolation valve of  FIG. 2  in accordance with an embodiment of the present invention; 
           [0016]      FIG. 4  is a second perspective view of driving member of  FIG. 3  in accordance with an embodiment of the present invention; 
           [0017]      FIG. 5  is a first perspective view of a cam driver of the isolation valve of  FIG. 2  in accordance with an embodiment of the present invention; 
           [0018]      FIG. 6  is a second perspective view of the cam driver of  FIG. 5  in accordance with an embodiment of the present invention; 
           [0019]      FIG. 7  is a partial cross-sectional view of a profile of a cam of the driving member of  FIG. 3  in accordance with an embodiment of the present invention; and 
           [0020]      FIG. 8  is a flow chart of a method for operating a fluid control system in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    The following detailed description is of the best currently contemplated modes of carrying out exemplary embodiments of the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims. 
         [0022]    Various inventive features are described below that can each be used independently of one another or in combination with other features. 
         [0023]    Broadly, embodiments of the present invention generally provide closed-loop fluid control systems in which sensor maintenance may be facilitated with a valve arrangement that isolates the sensors from a main fluid path of the system during removal and/or replacement of the sensors. Sensor removal may then proceed without a need to drain or de-pressurize the fluid in the system. The valve may block fluid flow to a plurality of the sensors simultaneously so that all sensors of the system may be replaced in a single maintenance cycle. Additionally, the valve arrangement may facilitate placement of the sensors in locations that are readily accessible for maintenance purposes. 
         [0024]    Referring now to  FIG. 1 , an exemplary embodiment of the invention may comprise a fluid control system  10  with a coolant distribution module  12  and various heat exchangers collectively designated by the numeral  14 . A main fluid path  16  may interconnect the coolant distribution module  12  with the heat exchangers  14 . A fluid  20  may be pressurized and circulated through the main fluid path  16  by a pump  22 . 
         [0025]    Fluid pressure may vary from one point to another as the fluid  20  passes through the system  10 . For example, a pressure drop may occur as the fluid  20  fluid passes through a filter  24 . A differential pressure sensor  26  may be incorporated into the fluid control system  10  so that the magnitude of the filter pressure drop may be continuously monitored. 
         [0026]    Fluid pressure may also vary at various other locations in the system  10 . Pressure sensors may be employed to monitor these pressure variations. For example, an absolute pressure sensor  28  may be employed to monitor pressure within the heat exchanger  14 . In an aircraft, the pressure sensor  28  may be paired with another sensor  30  to provide redundancy. Also, a redundant pair of differential pressure sensors  32  and  34  may be employed to monitor pressure differential between heat exchanger pressure and pressure in a cold plate  36 . 
         [0027]    It may be noted that the various pressure sensors of the system  10  may not be directly connected to their respective sensing locations. The sensors may be interconnected with their respective sensing locations through a sensor replacement valve or isolation valve  40 . 
         [0028]    For example, the pressure sensor  26  may be connected to the filter  24  with sensing tubes  26 - 1  and  26 - 2 . The sensing tube  26 - 1  may be tapped into the fluid path  16  at an inlet side  24 - 1  of the filter  24 . The sensing tube  26 - 2  may be tapped into the fluid path  16  at an outlet side  24 - 2  of the filter  24 . The sensing tubes  26 - 1  and  26 - 2  may be connected to the isolation valve  40 . The isolation valve  40  may be connected to the sensor  26  with sensing tubes  26 - 3  and  26 - 4 . In this regard, the sensor  26  may be considered to be indirectly connected to the filter  24  through a fluid-filled connection path  27  that includes the isolation valve  40 . 
         [0029]    In a manner that will be explained hereinafter in detail, the isolation valve  40  may be operated to block passage of the fluid  20  between the tubes  26 - 1  and  26 - 3  and between the tubes  26 - 2  and  26 - 4 . It may be seen that with such blocking, the sensor  26  may be removed from the sensing tubes  26 - 3  and  26 - 4  without a need to de-pressurize or drain the fluid  20  from the main fluid path  16 . 
         [0030]    Similarly, the sensors  28 ,  30 ,  32  and  34  may be indirectly connected to their respective pressure sensing locations through the isolation valve  40 . For example, the sensor  28  may be indirectly connected to the main fluid path  16  through a connection path  29  which may comprise sensing tube  28 - 1  and  28 - 2  and the isolation valve  40 . The isolation valve  40  may be employed to block passage of the fluid  20  to any or all of the sensors  26 ,  28 ,  30 ,  32  and/or  34 , thus facilitating their removal and replacement or repair without a need to depressurize or drain the fluid  20  from the closed-loop fluid path  16 . 
         [0031]    Referring now to  FIGS. 2 through 6 , exemplary operational and construction features of the isolation valve  40  may be understood. The isolation valve  40  may comprise a valve body  42  with a plurality of valve cylinders  44 ,  46 ,  48  and  50 . A corresponding plurality of valve pistons  52  may be positioned within the cylinders  44 ,  46 ,  48  and  50 . The pistons  52  may be spring-biased to a normally-open position with compression springs  53 . Fluid inlet ports  44 - 2 ,  46 - 2 ,  48 - 2 , and  50 - 2  and fluid outlet ports  44 - 3 ,  46 - 3 ,  48 - 3 , and  50 - 3  may be formed at closed ends  44 - 1 ,  46 - 1 ,  48 - 1  and  50 - 1  of the cylinders  44 ,  46 ,  48  and  50 . The fluid inlet ports and the fluid outlet ports may be connected to the sensing tubes shown in  FIG. 1 . For the cylinder  44 , for example, the fluid inlet port  44 - 2  may be connected to the pressure sensing tube  26 - 1  and the fluid outlet port  44 - 3  may be connected to the pressure sensing tube  26 - 3 . For the cylinder  46 , the fluid inlet port  46 - 2  may be connected to the pressure sensing tube  26 - 2  and the fluid outlet port  46 - 3  may be connected to the pressure sensing tube  26 - 4 . 
         [0032]    It may be seen that the inlet port  44 - 2  and the outlet port  44 - 3  may be simultaneously occluded by one of the pistons  52  when a free-end  52 - 1  of the piston  52  engages with the closed end  44 - 1  of the cylinder  44 . In an exemplary embodiment, the piston  52  may be provided with a compressible or deformable insert  52 - 3  which may deform into a shape of the closed end  44 - 1  of the cylinder  44 , thus ensuring full occlusion of the ports  44 - 2  and  44 - 3  when the piston  52  is engaged with the closed end  44 - 1 . When the inlet port  44 - 2  and the outlet port  44 - 3  are occluded, the sensor  26  may be isolated from the inlet  24 - 1  of the filter  24  of  FIG. 1 . Similarly, when the inlet port  46 - 2  and the outlet port  46 - 3  are occluded, sensor  26  may be isolated from the outlet  24 - 2  of the filter  24 . In other words, occlusion of the ports  44 - 2 ,  44 - 3 ,  46 - 2  and  46 - 3  may result in an isolation of the sensor  26  from the main fluid path  16 . When such isolation is achieved, the sensor  26  may be removed from the system  10  without a need to drain the fluid  20  from the system  10 . 
         [0033]    In an exemplary embodiment of the isolation valve  40 , a driving member  54  may be positioned within a cylindrical chamber  56  formed in the valve body  42 . An exemplary configuration for the driving member  54  may be illustrated in  FIGS. 3 and 4 . The driving member  54  may comprise a piston engaging surface  54 - 1 , a guiding sleeve  54 - 2  and an annular cam ring  54 - 3 . The driving member  54  may move axially within the chamber  56  as the guiding sleeve  54 - 2  engages with the chamber  56 . An aligning groove  54 - 2 - 1  may be formed in the guiding sleeve  54 - 2 . The groove  54 - 2 - 1  may engage with an aligning pin  58  which may project from the valve body  42  into the chamber  56 . Thus, the driving member  54  may not rotate about its axis as it moves axially within the chamber  56 . 
         [0034]    The driving member  54  may be positioned so that its piston engaging surface  54 - 1  may be engaged with contact ends  52 - 2  of the pistons  52 . The driving member  54  may be forced to move axially within the chamber  58  to overcome compressive spring force from the springs  53  so that the pistons  52  may be driven away from their normally open position. Axial movement of the driving member  54  may be imparted by interaction of the cam ring  54 - 3  and a cam driver  60 . In this regard the driving member  54  may be considered to be a cam-operated driving member 
         [0035]    The cam driver  60  (shown in detail in  FIGS. 5 and 6 ) may include a rotatable shaft  60 - 1  adapted to rotate within a mounting plate  60 - 2 . The mounting plate  60 - 2  may be attached to the valve body  42  so that the shaft  60 - 1  may align axially with the driving member  54 . Cam engaging pins  60 - 3  may be positioned at an inner end  60 - 1 - 1  of the shaft  60 - 1 . As the shaft  60 - 1  is rotated, the pins  60 - 3  may slide across the cam ring  54 - 3  and thus drive the driving member  54  axially within the chamber  56  (in an exemplary manner illustrated with particularity in  FIG. 7 ). Consequently the pistons  52  may be moved to a closed position in which the inlet and outlet ports of the cylinders  44 ,  46 ,  48  and  50  may be occluded. 
         [0036]    The cam driver  60  may be provided with an operating handle  60 - 4  at an outer end  60 - 1 - 2  of the shaft  60 - 1 . The operating handle  60 - 4  may have any one of many configurations. In an exemplary embodiment of the system  10 , the handle  60 - 4  may be hex shaped and may be readily rotated with a conventional socket wrench extension. This hex-shaped configuration may be particularly useful in fluid control systems that may be installed in confined spaces such equipment bays in aircraft. 
         [0037]    It may be also noted that when one of the fluid control systems is configured as described above, the sensors may be positioned in locations that are remote from their respective sensing locations. For example, in the system  10  of  FIG. 1 , the sensors  26 ,  28 ,  30 ,  32  and  34  may all be located on the coolant distribution module  12 . Thus all of the sensors may be readily accessible for maintenance purposes. 
         [0038]    In one embodiment of the present invention, a method is provided for removing a sensor from a fluid control system without draining fluid from the system (e.g. the system  10 ). In that regard the method may be understood by referring to  FIG. 8 . In  FIG. 8 , a flow chart may portray various aspects of a method  800 . In a step  802 , sensors may be provided to determine a state of fluid in a main fluid path of the system (e.g., the sensors  26 ,  28 ,  30 ,  32  and  34  may be provided to sense pressure at various locations in the fluid control system  10 ). In a step  804 , fluid-filled connection paths may be provided between the sensors and the main fluid path (e.g., the sensing tubes  26 - 1 ,  26 - 2 ,  26 - 3  and  26 - 4  and the isolation valve  40  may be provided to indirectly interconnect the sensor  26  to the main fluid path  16 ). In a step  806 , determination may be made of a need to repair or replace one or more of the sensors. In a step  808 , the isolation valve may be closed to isolate the sensors from the main fluid path (e.g., the valve  40  may be closed to interrupt fluid connection paths between the sensor  26  and the main fluid path  16 ). In a step  810 , one or more of the sensors may be removed from the system for repair or replacement without draining fluid from the system. 
         [0039]    It should be understood, of course, that the foregoing relates to exemplary embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.