Abstract:
Provided is an apparatus for connecting two sub-flow systems (e.g. airplane fuel tanks) and conveying a fluid between the two sub-systems using a pressured balanced transfer tube, particularly when there are large radial and axial movements or offsets between the sub-systems. Unlike conventional fluid transfer systems, the present apparatus allows for the pressure in the transfer tube to be balanced to internalize the pressure forces and prevent the exertion of pressure forces on the sub-systems connected to the transfer tube.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/081,467 filed Jul. 17, 2008, which is hereby incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     The present invention relates generally to fluid transfer, and more particularly to fluid transfer tubes between two sub-systems. 
     BACKGROUND 
     Tubes, hoses or bellows can be used to transfer fluid between two components in industrial, automotive and aeronautical applications. These fluid transfer devices have to take into account the space between the components, the diameters of the flow passages, and the radial and axial movements caused by the tolerances of the components and the dynamic environments during fluid transfer. In a typical fluid transfer device, a transfer tube that is capable of expanding and contracting can be used to take into account the axial movements of the sub-systems. Additionally, the transfer tube can be jointed to take into account the radial movements of the sub-systems. 
     In commercial and military airplane auxiliary fuel tank systems, the fuel tank storage volume or the number of fuel tanks will be adjusted according to the distance of the destination for the purpose of saving fuel and increasing fuel usage efficiency. Tubes, hoses and bellows can be used to connect the auxiliary fuel tanks of the airplanes and to transfer the fuel from one tank to another. Further, to transfer fuel from a refueling tank to an empty tank, a moving duct system of the fuel tank can be unfolded and a docking head extended out to dock to the refueling tank. One or more tubes, hoses, etc. can be used to couple the docking head to the fuel tank. The fuel will transfer from the refueling tank to the fuel tank through the docking head and the one or more tubes, hoses, etc. of the moving duct system. 
     SUMMARY OF INVENTION 
     The present invention provides an apparatus and method for connecting two sub-flow systems (e.g. airplane fuel tanks) and conveying a fluid between the two sub-systems using a pressured balanced transfer tube, particularly when there are large radial and axial movements or offsets between the sub-systems. Unlike conventional fluid transfer systems, the present apparatus and method allow for the pressure in the transfer tube to be balanced to internalize the pressure forces and prevent the exertion of pressure forces on the sub-systems connected to the transfer tube. This is of particular benefit when the pressure balanced transfer tube is connecting high pressure systems. 
     More particularly, the apparatus comprises first and second inner housings and a transfer housing in which axially inner portions of the inner housings move telescopically. The first and second inner housings each have an inner end that is closed and sealed to the transfer housing. The inner housings also have an annular side wall surrounding an interior passage for fluid flow, and each side wall has an opening extending to a radially outward surface of the inner housing. The transfer housing has a transfer passage extending between openings at opposite ends thereof that open to an interior surface of the transfer housing for communicating with the openings in the inner housings over a range of telescopic movement. A fluid flow path is formed allowing the housings to be pressure balanced. 
     The apparatus may comprise at least one fitting having an outer end configured to couple to a sub-system and in inner end configured to pivotally couple to one of the first or second inner housings to provide relative pivotal movement of the transfer tube. 
     The transfer housing may further comprise an inner tubular member and an outer tubular member, with the inner tubular member including the openings at opposite ends that communicate with the openings in the inner housing. The inner and outer tubular members form therebetween a transfer passage extending between the openings. 
     The apparatus may further comprise a vent located between spaced apart inner ends of the inner housings to maintain the internal chamber at or near atmospheric pressure to allow for axial movement of the inner housings relative to one another. In particular, the vent may be formed by a centrally located venting tube in the transfer housing connecting the internal chamber to atmosphere. 
     In still another embodiment the apparatus may include an annular containment member surrounding each inner housing and the transfer housing, the annular containment member being in a radially spaced relationship to the inner housings and the transfer housing so as to form a containment flow path for capturing any fluid leakage from the fluid flow path. 
     Moreover, the present invention provides a method for transferring a fluid between first and second moving sub-systems using a pressure balanced transfer tube fluidly connecting the sub-systems. The method comprises receiving the fluid from the first sub-system at a first end of the transfer tube, transferring the fluid from the first end to a second end of the transfer tube via a series of housings. The series of housings include first and second inner housings and a transfer housing in which axially inner portions of the inner housings move telescopically. The first and second inner housings each have an inner end that is closed and sealed to the transfer housing. The inner housings also have an annular side wall surrounding an interior passage for fluid flow, and each side wall has an opening extending to a radially outward surface of the inner housing. The transfer housing has a transfer passage extending between openings at opposite ends thereof that open to an interior surface of the transfer housing for communicating with the openings in the inner housings over a range of telescopic movement. The method includes transferring the fluid from the second end to the second sub-system, and moving the transfer tube axially and radially when needed to account for movement of the sub-systems. 
     The foregoing and other features of the invention are hereinafter described in greater detail with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional view of an exemplary flange fitting pressure balanced transfer tube according to the invention, shown at a minimum length; 
         FIG. 1A  is an end view of the flange fitting pressure balanced transfer tube taken substantially along the line  1 A- 1 A of  FIG. 1 ; 
         FIG. 2  is a cross-sectional view of the flange fitting pressure balanced transfer tube, shown at a maximum length; 
         FIG. 3  is a cross-sectional view of the flange fitting pressure balanced transfer tube, shown pivoted and at the minimum length; 
         FIG. 4  is a cross-sectional view of another embodiment of the pressure balanced transfer tube, shown at a minimum length and provided with a different end fitting; 
         FIG. 4A  is an end view of the pressure balanced transfer tube taken substantially along the line  4 A- 4 A of  FIG. 4 ; 
         FIG. 5  is a cross-sectional view of another embodiment of the pressure balanced transfer tube, shown at a maximum length and provided with a different end fitting; 
         FIG. 6  is a cross-sectional view of an exemplary triangle flange elbow fitting pressure balanced transfer tube in accordance with the invention, shown at a minimum length; 
         FIG. 7  is a cross-sectional view of the triangle flange elbow fitting pressure balanced transfer tube, shown at a maximum length; 
         FIG. 7A  is an end view of the triangle flange elbow fitting pressure balanced transfer tube taken substantially along the line  7 A- 7 A of  FIG. 7 ; 
         FIG. 8  is another cross-sectional view of the triangle flange elbow fitting pressure balanced transfer tube, shown at a minimum length; 
         FIG. 9  is a front view of the triangle flange elbow fitting pressure balanced transfer tube; 
         FIG. 10  is a side view of the triangle flange elbow fitting pressure balanced transfer tube; 
         FIG. 11  is a bottom view of the triangle flange elbow fitting pressure balanced transfer tube; 
         FIG. 12  is a cross-sectional view of an exemplary dual wall pressure balanced transfer tube according to the invention, shown at a minimum length and provided with a flange fitting; 
         FIG. 12A  is an end view of the dual wall pressure balanced transfer tube taken substantially along the line  12 A- 12 A of  FIG. 12 ; 
         FIG. 13  is a cross-sectional view of the dual wall pressure balanced transfer tube, shown at a maximum length and provided with a flange fitting; 
         FIG. 14  is a cross-sectional view of the dual wall pressure balanced transfer tube, shown pivoted and at a minimum length and provided with a flange fitting; and 
         FIG. 14A  is a cross-sectional view of a vent of the dual wall pressure balanced transfer tube taken substantially along the line  14 A- 14 A of  FIG. 14 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring initially to  FIGS. 1-3 , an exemplary embodiment of a flange fitting pressure balanced transfer tube  10  is shown. The transfer tube may be used for various fluid transfer systems, such as aircraft refuelling systems, hydraulic systems, cooling systems, etc. The transfer tube provides a solution that allows for fluid to be conveyed from sub-system  12  to sub-system  14 , and can accommodate for a mismatch in sub-system positions and/or limited connection space, without pressure forces being exerted on the sub-systems. The transfer tube can also accommodate for large relative radial and axial movements that are caused by the sub-systems  12  and  14 , which may arise, for example, by the effects of thermal expansion and contraction, and by cyclic, radial and axial motion of the transfer tube in the dynamic environment. 
     Referring now in detail to  FIGS. 1 and 1A , the flange fitting pressure balanced transfer tube  10  generally comprises two inner housings  28 , where each inner housing may be identical as illustrated, and a transfer housing  36 , the coupling of which forms a flow passage from a first end of the transfer tube to a second end of the transfer tube (illustrated in  FIG. 3 ). A fitting, such as an exemplary fitting  20 , may be provided at the end of one or both of the inner housings  28  for connecting the transfer tube to a sub-system. In some embodiments, one or both inner housings may be integrally formed with a sub-system. 
     Each illustrated fitting  20  has an outer end that may be configured to couple to a sub-system  12 ,  14 , which can include a tank, such as an auxiliary fuel tank, a vessel, etc., to fluidly couple the transfer tube  10  to the sub-system. The transfer tube can be coupled to the sub-systems by bolting each fitting  20  to the respective sub-system via apertures  24 , although other coupling means can be used to couple the fittings  20  to the sub-systems such as standard fittings, quick-connect couplings, etc. 
     One or both fittings (as illustrated) may be pivotally coupled to the respective inner housing  28 . As illustrated, each fitting  20  has an inner end that can be configured to couple to a respective outer end of the inner housings  28  to provide relative pivotal movement by a pressure tight pivot joint  26 . A suitable seal may be provided, such as O-ring  80  to seal the fittings  20  to the sub-systems. Additionally, the joints  26  may be provided with grooves, such as dovetail seal grooves, to carry a suitable seal, such as O-ring  82  to seal the fittings  20  to the inner housings  28 . 
     The outer end of each inner housing  28  has an inner spherical surface that engages a corresponding spherical surface of the respective fittings  20 , thereby forming the joint  26 . Similarly, each inner housing  28  has an outer spherical surface that engages a corresponding inner spherical surface of a cover  52  that allows for such movement. Each cover  52  also has a cylindrical portion that telescopes over a cylindrical portion of the respective fittings  20  and may be retained in place by a retainer wire  50  or other suitable means. Other means may also be provided to hold each inner housing  28  and each fitting  20  together while still providing for relative pivotal movement and fluid communication from an interior flow passage  20 A in the fitting  20  to an interior flow passage  22  of each inner housing  28 . 
     The interior flow passage  22  of each inner housing  28  may be formed by a tubular member having a closed end  30  and an annular side wall  32  surrounding the interior passage  22 . Each side wall  32  has one or more radial openings  34  extending to a radially outward surface of each inner housing  28  to communicate with one or more radial openings  40  in the transfer housing  36 . The openings  34  in the annular side walls  32  are used to allow fluid to flow from one end of the transfer tube  10  to the other without fluid flowing through an internal chamber  78  located interiorly of the transfer tube  10  between the spaced apart closed ends  30  of the inner housings  28 . 
     The transfer housing  36  includes an inner wall and an outer wall forming therebetween a transfer passage  44  that extends between the openings  40 . In the illustrated embodiment, the inner wall may be formed by an inner tubular member  38  and the outer wall may be formed by the outer tubular member  42 . Axial ends of the inner tubular member  38  may be sealed to axial ends of the outer tubular member  42  by suitable means, such as O-ring  88  and back-up O-rings  90 . As shown, the outer tubular member  42  may be axially fixed in place relative to the inner tubular member  38  by a retainer wire  58  or other suitable means. As will become apparent below, the retainer wire  58  is redundant with another mechanism for holding the outer tubular member  42  axially in place relative to the inner tubular member  38 . If the retainer wire  58  is not used, the space it would have occupied would be filled by materials of the inner and outer tubular members. 
     As shown, the transfer passage  44  extends between the openings  40  in the inner tubular member  38  at opposite ends of the transfer passage  44 , thereby fluidly coupling the openings  40 . Each inner housing  28  includes axially inner portions that move telescopically in the transfer housing  36  relative to the inner tubular member  38 . The openings  40  open to an interior surface of the inner tubular member  38  for communicating with the openings  34  in each inner housing  28  over a range of telescopic movement. The openings  34  are axially elongated to maintain communication with the openings  40  over the range of telescopic movement. Suitable seals may be provided, such as O-rings  84  and  92  and back-up O-rings  86  and  94  that are carried by piston grooves to seal each inner housing  28  to the inner tubular member  38 . 
     To maintain the internal cavity  78  at or near atmospheric pressure to allow for axial movement of the inner housings  28  relative to one another, the transfer tube  10  also includes a vent  46 . When fluid is flowing through the transfer tube, the fluid flows around the vent  46 . The vent  46  includes a vent tube  47  that extends diametrically through the transfer tube and is held in place by a cap  48 , which may be in the form of a tubular sleeve, that may be fixed to the transfer tube by a retainer wire  59  or other suitable means. The vent tube may be sealed to the inner and outer tubular members  38  and  42  by suitable seals, such as O-rings  96  and  98 , and the walls of the inner and outer tubular members  38  and  42  may be radially thickened to accommodate the seals  96  and  98 , although other sealing mechanisms may be utilized. The outer tubular member  42  may be axially fixed in place relative to the inner tubular member  38  by the vent tube  47 . 
     To maintain the same pressure in the internal chamber  78  as or near the atmosphere, the vent tube  47  has one or more venting holes  74  communicating with the internal chamber  78  and the ends of the tube  47  are open. The open ends of the tube  47  communicate with one or more axially extending grooves  76  on an interior surface of the cap  48  that extend to the exterior of the transfer tube for communicating with the atmosphere. The vent  46  may also includes gaps between the cap  48  and the outer tubular member  42  and openings, such as annular through slots (not shown), both of which may be added on the cap  48  to increase the efficiency of ventilation. 
     As will now be appreciated, the foregoing construction of the transfer tube  10  is pressure balanced. This arises from the inner housings  28  having a closed end  30  causing fluid to flow indirectly through the transfer tube  10 , thereby preventing fluid pressure from acting on inner axially facing surfaces of the inner housings  28  that otherwise would act to apply an axially outwardly directed force to each inner housing  28 . Since the closed ends  30  prevent direct transfer of fluid from one inner housing  28  to the other, fluid flow is indirectly passed from one inner housing  28  to other via openings  34  and  40  and the transfer passage  44  in the transfer housing  36 . 
     By being pressure balanced, the inner housings  28  can freely move and rotate around any axis along the flow directions based on the movement of the sub-systems, while allowing for a seal tight connection with the sub-systems. Further, by being pressure balanced, the transfer tube  10  will not exert pressure forces on the sub-systems causing leakage and/or damage to the sub-systems or the transfer tube, and the transfer tube will not be extended to its maximum length by the internal pressure in the housings. Similar to the inner housings  28 , the inner tubular member  38  and the outer tubular member  42  are pressure balanced. Pressure forces are not applied to the inner tubular member  38  and the outer tubular member  42 , and therefore, the transfer tube design also eliminates pressure loading on the vent  46 , retainer wires  56  and  58 , and stop segments  54  within the maximum extended length of the transfer tube. 
     Referring now to  FIGS. 1 and 2 ,  FIG. 1  shows the transfer tube  10  in a retracted position LMIN and  FIG. 2  shows the transfer tube in an extended position LMAX. The transfer tube is designed so that no matter what position the transfer tube is in (retracted position LMIN, intermediary position, etc.), the fluid flow does not cause the transfer tube to move out of that position. Instead, it is the movement of sub-systems that cause the transfer tube to move out of its position. Conventional transfer tubes, however, cannot prevent further extension under pressure of the fluid. The conventional transfer tubes will be forced to extend, placing pressure on the sub-systems and causing damage and/or leakage to the sub-systems and the conventional transfer tube. 
     As shown in  FIG. 2 , transfer tube  10  is fully extended, i.e. the inner portions of each inner housing  28  have moved telescopically in the transfer tube relative to the inner tubular member  38 , away from the center of the transfer tube. The openings  34  remain in fluidic communication with the openings  40 , allowing the fluid to continue to flow through the transfer tube during movement. Stop segments  54 , which can be provided as two half segments, are provided on the outside of the transfer tube to assist in preventing the transfer tube from extending when it reaches its maximum extended position LMAX. The stop segments  54  may be secured in the ends of the inner tubular member  38  by retainer wires  56  or other suitable means. The retainer wires  56  may be positioned in a groove in the inner tubular member  38 , and the stop segments  54  positioned through exterior loading holes in the inner tubular member  38 . 
     Referring now to  FIG. 3 , the transfer tube  10  is shown at a radial misalignment, and the direction of the fluid flow as it flows through the transfer tube is shown by a series of arrows. The end surfaces of the fittings  20  are shown as being parallel to each other, although there is no requirement that they be parallel. When the transfer tube is experiencing a radial misalignment between the fittings  20  during installation or operation of the transfer tube, the joints  26  allow for 360 degree rotation around the flow axis of the transfer tube and a designed angular pivotal movement of the transfer tube. When the misalignment occurs, the transfer tube moves such that the fittings  20  may be pivoted at an angle A° from each other when the right side of the transfer tube moves a distance D relative to the left side of the transfer tube or vice versa. As shown, the original pivot point of the joint  26  on the left side of  FIG. 3  is represented as C 1 , the new pivot point of the joint  26  on the right side of  FIG. 3  is represented as C 3 , and the pivot point of the joint  26  on the right side of  FIG. 3  prior to movement of the transfer tube is represented as C 2  (where distance D is equal to the distance from C 2  to C 3 ). In order to accommodate the radial movement on the transfer tube, each joint  26  can rotate counter-clockwise around their pivots at angle A°. 
     To accomplish the foregoing, the inner housing  28  on the left side of the transfer tube  10  rotates A° counter-clockwise around the pivot point C 1  and the inner housing  28  on the right side of the transfer tube rotates the same amount counter-clockwise around pivot point C 3 . During the pivotal movement, the inner housings  28  can move telescopically in the inner tubular member  38  to adjust to the length required to achieve the pivot angle for the transfer tube. The rotational movement of the joints  26  and the telescopic movements of the inner housings  28  may be synchronized to achieve the pivot angle of one end of the transfer tube relative to the other. Further, when the transfer tube is in the extended position, it may have more pivoting capacity than in the retracted position. 
     Referring now to  FIGS. 4 ,  4 A and  5 , an exemplary embodiment of a pressure balanced transfer tube  110  is shown provided with a different end fitting, in particular a fitting having a threaded end for threading into a bore in the sub-system. The transfer tube is substantially the same as the above-referenced transfer tube  10 , and consequently the same reference numerals, but indexed by  100  are used to denote structures corresponding to similar structures in the transfer tube  110 . In addition, the foregoing description is equally applicable to the transfer tube  110  except as noted below. The standard fitting pressure balanced transfer tube operates in a similar manner as the transfer tube  10  described above, except for the differences herein described. 
       FIG. 4  shows the transfer tube in a retracted position LMIN and  FIG. 5  shows the transfer tube in an extended position LMAX. Referring now in detail to  FIG. 4 , the transfer tube  110  includes two inner housings  128 , where each inner housing  128  includes an outer swiveling surface that is coupled to a swiveling surface of a nut  160 , shown with but not limited to having six sides, to form a pressure tight joint  126 , the joint  126  being held in place by the nut  160 . The nuts  160  replace the covers  52  and the retainer wires  50  shown in  FIG. 1 . Each nut  160  may be threaded onto each fitting  120  and locked in place by swaged tips of a T-locking ring  162 , which locks into slots in the fittings  120  and the nuts  160 . Shims  164 , disposed next to each T-locking rings  162 , can be used to adjust and control an extrusion gap of each joint  126  in higher pressure applications. 
     There are seal grooves in the pressure tight joints  126  of the fittings  120  to carry the pressure tight joint seals, i.e. O-rings  182  and delta back-up rings  168 . The back-up rings  168  can be included in the assembly when the transfer tube  110  is used for high pressure and dirty environment applications. Also included for high pressure and dirty environment applications are back-up rings  197  and  199 , configured around the back pressure side of O-rings  196  and  198 . Such rings are not required, however, and especially not when the transfer tube is used for low pressure and clean environment applications. If the delta back-up rings  168  and back-up rings  197  and  199  are not included, the space where the rings were located would be occupied by fitting and housing materials. Additionally, bearings  166  may be included and used in-between the swiveling surfaces forming each joint  126 . If the bearings  166  are not included, the space where the bearings  166  were located would be occupied by the nut material and the nuts  160  would be coated with a surface hardening coating on its swiveling surface. 
     Referring now to  FIGS. 6-11 , an exemplar embodiment of a flange elbow fitting pressure balanced transfer tube  210  is shown. The transfer tube is substantially the same as the above-referenced transfer tube  10 , and consequently the same reference numerals, but indexed by  200  are used to denote structures corresponding to similar structures in the transfer tube  210 . In addition, the foregoing description of the transfer tube  10  is equally applicable to the transfer tube  210  except as noted below. As illustrated,  FIG. 6  shows the transfer tube in a retracted position LMIN and  FIG. 7  shows the transfer tube in an extended position LMAX.  FIG. 8  shows another cross-sectional view of the transfer tube,  FIG. 9  shows a front view of the transfer tube,  FIG. 10  shows a side view of the transfer tube, and  FIG. 11  shows a bottom view of the transfer tube. The flange elbow fitting pressure balanced transfer tube  210  operates in a similar manner as the transfer tube  10  described above, except for the differences herein described. 
     Referring now to in detail to  FIGS. 6-8 , the transfer tube  210  includes two elbow inner housings  228  that allow the transfer tube  210  to swivel around one of the elbow inner housings  228  axes to increase circular maneuverability of fittings  220  that have an electrical bonding surface. Each cover  252  and each fitting  220  include slots to house an anti-rotation pin  266 , whereby the anti-rotation pins  266  are provided to prevent the relative rotation of the covers  252  to the fittings  220  during the swiveling of one of the fittings  220  relative to the other. 
     Scraper rings  260  are provided and may be used on the bearing surfaces of each joint  226  to reduce the friction between the swiveling surfaces of the joints  226  and to prevent the sealing surfaces of the joints  226  from being contaminated. The scraper rings  260  can be included in the assembly when the transfer tube  210  is used for high pressure and dirty environment applications. Such rings  260  are not required, however, and especially not when the transfer tube  210  is used for low pressure and clean environment applications. If the scraper rings  260  are not included, the space where the rings  260  were located would be occupied by the fittings material. Also provided are inner housing plugs  262 , which are provided at inner ends of each inner housing  228 . The inner housing plugs  262  may be used to close and seal the inner ends of the inner housings  228  to the transfer tube to prevent fluid from entering the internal chamber  278 . Smalley retainer rings  264  may be provided to secure the inner housing plugs  262  in the inner housings  228 , and suitable seals, such as O-rings  279  may be provided to seal the inner housing plugs  262  to the inner housings  228 . 
       FIG. 8  additionally shows an installation form for stop segments  255 , provided in two semi circular halves. The stop segments  255  are installed over the outside of the inner tubular member  238  and the shoulders of the stop segments  255  are engaged into the groove in the inner tubular member  238 . Circular stop sleeves  257  may then be slide over the stop segments  255  to secure them in the place, and the stop sleeves fixed in place relative to the inner tubular member  238  by a retainer wire  258  or other suitable means. 
     Further, the flange elbow fitting pressure balanced transfer tube  210  may include only one of back-up ring  286  and  294  located beside each O-ring  284  and  292 , respectively. Alternatively, the design may eliminate the back-up rings  286  and  294  as shown in  FIG. 8 , to shorten the overall length of the transfer tube. To further shorten the length of the transfer tube in  FIG. 8 , two vent tubes  247  may be provided, which are narrower than the vent tube  47  shown in  FIG. 1 . To seal the vent tubes  247 , seals  296  and  298  are carried by the vent tube  247  as opposed to being carried by the inner tubular member  38  and the outer tubular member  42  as shown in  FIG. 1 . 
     Referring now to  FIGS. 12-14A , an exemplary embodiment of a dual wall pressure balanced transfer tube  310  is shown that may be used for various fluid transfer systems, such as an aircraft pylon/wing interface to provide a shrouded flexible connection. The transfer tube  310  is substantially the same as the above-referenced transfer tube  10 , and consequently the same reference numerals, but indexed by  300  are used to denote structures corresponding to similar structures in the transfer tube  10 . 
     Referring now in detail to  FIGS. 12 ,  12 A and  13 , the dual wall pressure balanced transfer tube  310  generally comprises two inner housings  328 , where each inner housing may be identical as illustrated, and a transfer housing  336 , the coupling of which forms a flow passage from a first end of the transfer tube to a second end of the transfer tube (illustrated in  FIG. 14 ). A fitting, such as exemplary fitting  320 , may be provided at the end of one or both of the inner housings  328  for connecting the transfer tube to a sub-system. In some embodiments, one or more transfer tubes may be integrally formed with a sub-system. 
     Each illustrated fitting  320  has an outer end that is configured to couple to a sub-system  312 ,  314 , such as an auxiliary fuel tank, to fluidly couple the transfer tube  310  to the sub-system. The transfer tube  310  can be coupled to the sub-systems by bolting each fitting  320  to the respective sub-system via apertures  324 , although other coupling means can be used to couple the fittings  320  to the sub-systems such as standard fittings, quick-connect couplings, etc. 
     One or both fittings (as illustrated) may be pivotally coupled to the respective inner housing  328 . As illustrated, each fitting  320  has an inner end that can be configured to couple to a respective outer end of the inner housings  328  to provide relative pivotal movement by a pressure tight pivot joint  326 . Suitable seals may be provided, such as O-rings  380  and  381  to seal the fittings  320  to the sub-systems and another seal, such as O-ring  383  may be provided to seal each fitting  320  to covers  352 . The outer end of each inner housing  328  has an inner spherical surface that engages a corresponding spherical surface of the respective fittings  320 , thereby forming the joint  326 . Each outer sliding housing  362  has a cylindrical portion that telescopes over a cylindrical portion of each inner housing  328  and is held in place by the cover  352  and shoulder of the inner housings  328 . Additionally, each outer sliding housing  362  has an outer spherical surface that engages a corresponding inner spherical surface of covers  352  that forms an outer joint  368  and allows for pivotal movement. Each cover  352  also has a cylindrical portion that telescopes over a cylindrical portion of the respective fittings  320  and may be retained in place by a retainer wire  350  or other suitable means. Joints  326  and  368  may be provided with grooves, such as dovetail seal grooves, to carry a suitable seal, such as O-rings  382  and  385 . Other means may also be provided to hold each inner housing  328 , outer sliding housing  362 , and fitting  320  together while still providing for relative pivotal movement and fluid communication from an interior flow passage  320 A in the fitting  320  to an interior flow passage  322  of each inner housing  328 . 
     The interior flow passage  322  of each inner housing  328  may be formed by a tubular member having a closed end  330  and an annular side wall  332  surrounding the interior passage  322 . Each side wall  332  has one or more radial openings  334  extending to a radially outward surface of each inner housing  328  to communicate with one or more radial openings  340  in the transfer housing  336 . The openings  334  in the annular side walls  332  are used to allow fluid to flow from one end of the transfer tube  310  to the other without fluid flowing through an internal chamber  378  located interiorly of the transfer tube between the spaced apart closed ends  330  of the inner housings  328 . 
     The transfer housing  336  includes an inner wall and an outer wall forming therebetween a transfer passage  344  that extends between the openings  340 . In the illustrated embodiment, the inner wall is formed by an inner tubular member  338  and the outer wall is formed by the outer tubular member  342 . Axial ends of the inner tubular member  338  may be sealed to axial ends of the outer tubular member  342  by suitable means, such as O-ring  388  and back-up O-rings  390 . As shown, the outer tubular member  342  may be axially fixed in place relative to the inner tubular member  338  by a vent tube  347 . 
     As shown, the transfer passage  344  extends between the openings  340  in the inner tubular member  338  at opposite ends of the transfer passage  344 , thereby fluidly coupling the openings  340 . Each inner housing  328  includes axially inner portions that move telescopically in the transfer housing  336  relative to the inner tubular member  338 . The openings  340  open to an interior surface of the inner tubular member  338  for communicating with the openings  334  in each inner housing  328  over a range of telescopic movement. The openings  334  are axially elongated to maintain communication with the openings  340  over a full range of motion during the telescopic movement. Suitable seals may be provided, such as O-rings  384  and  392  and back-up O-rings  386  and  394  that are carried by piston grooves to seal each inner housing  328  to the inner tubular member  338 . 
     To maintain the internal cavity  378  at or near atmospheric pressure to allow for axial movement of the inner housings  328  relative to one another, the transfer tube  310  also includes a vent  346 . When fluid is flowing through the transfer tube, the fluid flows around the vent  346 . The vent  346  includes a vent tube  347  that extends diametrically through the transfer tube and may be held in place by an outer sliding sleeve cover  366 , which may be in the form of a tubular sleeve, that may be fixed to the transfer tube by retainer wires  358  or other suitable means. The vent tube may be sealed to the inner and outer tubular members  338  and  342  by suitable seals, such as O-rings  396  and  398 , and the walls of the inner and outer tubular members  338  and  342  may be radially thickened to accommodate the seals  396  and  398 , although other sealing mechanisms may be utilized. 
     To maintain the same pressure in the internal chamber  378  as or near the a containment flow path  360 , the vent tube  347  has one or more venting holes  374  communicating with the internal chamber  378  and the ends of the tube  347  are open. The open ends of the tube  347  communicate with one or more axially extending grooves  376  in an outer sliding sleeve cover  366  that extend to the exterior of the transfer tube for communicating with the atmosphere. The vent  346  may also includes gaps between the outer sliding sleeve cover  366  and the outer tubular member  342  and openings, such as annular through slots (not shown), that may be added on the outer sliding sleeve cover  366  to increase the efficiency of ventilation. 
     Surrounding the inner housings  328  and the inner and outer tubular members  338  and  342  is an annular containment member  361 , which is in a radially spaced relationship to the inner housings and the inner and outer tubular members. The annular containment member  361  may be formed by the fittings  320 , the outer sliding housings  362 , the outer sliding sleeve  364 , and the outer sliding sleeve cover  366 . The annular containment member  361  forms the containment flow passage  360  to allow leaking fluid to flow through the passage over a range of telescopic motion. This may be accomplished by the outer sliding sleeve  364  being in sliding relation to the outer sliding housing  362  on the left side of the transfer tube  310 . Suitable seals, such as O-rings  387  and back-up rings  389  are provided to seal the outer sliding housing to the outer sliding sleeve  364 . Further, an outer sliding sleeve cover  366  may be in sliding relation to the outer sliding housing  362  on the right side of the transfer tube. Suitable seals, such as O-rings  395  and  397  are provided to seal the outer sliding sleeve  362  to the outer sliding sleeve cover  366 . The outer sliding sleeve  364  is surrounded by the outer sliding sleeve cover  366 , which may be fixed in place relative to the outer sliding sleeve  364  by suitable means, such as retainer wire  358 . Suitable seals, such as O-rings  391  and back-up rings  393  are provided to seal the outer sliding sleeve  364  to the outer sliding sleeve cover  366 . 
     The annular containment member  361  forms the containment flow passage  360  for capturing any fluid leakage from the fluid flow path, without affecting the pressure forces of the transfer tube  310 . When operating without leakage, fluid is not flowing through the containment flow passage  360  and the pressure in the containment flow passage  360  may be about equivalent to atmospheric pressure. As shown, there are flow holes  370  in each fitting  320  and outer sliding housing  362 , and flow slots  372  on the sides and top of the outer tubular member  342 , both of which allow fluid to flow to and from the containment flow passage  360 , thereby allowing fluid to flow from one end of the transfer tube to the other if there is leakage. 
     The containment flow passage  360  may be provided so that in the event of a leak due to damage, contamination, or an incident during operation, the leaking fluid will flow along the containment flow passage  360  to a sensor cavity. The leaking can then be detected by a sensor (not shown) and be contained by an outer wall of the transfer tube  310 . Any leakage will be detected by the sensor and the sensor can then output an indication of fluid leakage to an operator, electronic warning system, etc. Any leaking fluid will remain sealed inside the containment flow passage  360 , providing a redundant sealing mechanism. 
     As stated above, the foregoing construction of the transfer tube  310  is pressure balanced. In normal operating conditions, pressure forces are not applied to the inner housings  328  or the inner and outer tubular members  338  and  342 , and therefore, the transfer tube design also eliminates pressure loading on the vent  346 , retainer wires  356  and  359 , and stop segments  354  and  363  within the maximum extended length of the transfer tube  310 . 
     Referring now to  FIGS. 12 and 13 ,  FIG. 12  shows the transfer tube  310  in a retracted position LMIN and  FIG. 13  shows the transfer tube in an extended position LMAX. As shown in  FIG. 13 , transfer tube  310  is fully extended, i.e. the inner portions of each inner housing  328  have moved telescopically in the transfer tube relative to the inner tubular member  338 , away from the center of the transfer tube. The openings  334  remain in fluidic communication with the openings  340 , allowing the fluid to continue to flow through the transfer tube during movement. Each outer sliding housing  362  and the outer sliding sleeve  364  can slide relative to each other to follow the adjusted length of transfer tube. Similarly, each outer sliding housing  362  and outer sliding sleeve cover  366  can slide relative to each other to follow the adjusted length of transfer tube. 
     Stop segments  354  and  363 , which can be provided as two half segments, are provided on the outside of the transfer tube  310  to assist in preventing the transfer tube  310  from extending when it reaches its maximum extended position LMAX. On the left side of the transfer tube, the stop segment  354  may be secured in the ends of the outer sliding sleeve  364  by a retainer wire  356  or other suitable means. The retainer wire  356  may be positioned in a groove in the outer sliding sleeve  364  and the stop segment  354  positioned through exterior loading holes in the outer sliding sleeve  364 . On the right side of the transfer tube  310 , the stop segment  363  may be secured in the ends of the outer sliding sleeve cover  366  by retainer wire  359 , which may be positioned in a groove in the outer sliding sleeve cover  366  and the stop segment  363  positioned through exterior loading holes in the outer sliding sleeve cover  366 . 
     Referring now to  FIGS. 14 and 14A , the transfer tube  310  is shown at a radial misalignment, and the direction of the fluid flow as it flows through the transfer tube is shown by a series of arrows. The end surfaces of the fittings  320  are shown as being parallel to each other, though there is no requirement that they be parallel. When the transfer tube is experiencing a radial misalignment between the fittings  320  during installation or operation of the transfer tube, the joints  326  allow for 360 degree rotation around the flow axis of the transfer tube and a designed angular pivotal movement of the transfer tube. When the misalignment occurs, the transfer tube moves such that the fittings  320  may be pivoted at an angle A° from each other when the right side of the transfer tube moves a distance D relative to the left side of the transfer tube or vice versa. As shown, the original pivot point of the joint  326  on the left side of  FIG. 14  is represented as C 1 , the new pivot point of the joint  326  on the right side of  FIG. 14  is represented as C 3 , and the pivot point of joint  326  on the right side of  FIG. 14  prior to movement of the transfer tube is represented as C 2  (where distance D is equal to the distance from C 2  to C 3 ). In order to accommodate the radial movement on the transfer tube, each joint  326  can rotate counter-clockwise around their pivots at angle A°. 
     To accomplish the foregoing, the inner housing  328  on the left side of the transfer tube  310  rotates A° counter-clockwise around the pivot point C 1  and the inner housing  328  on the right side of the transfer tube rotates the same amount counter-clockwise around pivot point C 3 . During the pivotal movement, each inner housing  328  and outer sliding housing  362  may move telescopically in the inner tubular member  338 , outer sliding sleeve  364  and outer sliding sleeve cover  366  to adjust to the length required to adjust the pivot angle for the transfer tube. The rotational movement of the joints and the telescopic movements of the inner housings  328  and the outer sliding housings  362  can be synchronized to achieve the pivot angle of one end of the transfer tube  310  relative to the other. Further, when the transfer tube is in the extended position, it may have more pivoting capacity than in the retracted position. 
     The transfer tubes (fittings, housings, etc.) and other components of the device can be made of any suitable material, such as, for example an aluminum alloy coated with hard anodize/PTFE, stainless steel (CRES 15-5PH, AMS5659, CRES 300 Series, etc.), or titanium alloy (GR 6AL-4V, AMS 4928, etc.). The swiveling and sealing surfaces of the transfer tubes may be coated with Nedox SF-2, Niflor, or an equivalent surface hardening coating. The O-rings may be made of Florosilicone or rubber that is compatible with the system fluid to be used. The back-up rings and scraper rings may be made of Teflon per MIL-R-8791/ASTM D1710. 
     The stop segments, stop sleeve, vent, cap, cover, outer sliding sleeve, outer sliding sleeve cover and other components of the device can be made of any suitable material, such as, for example an aluminum alloy coated with hard anodize/PTFE, stainless steel (CRES 15-5PH, AMS 5659 or CRES 300 Series or equivalent), or titanium alloy (GR 6AL-4V, AMS 4928 or equivalent). The stop segments can additionally be made from Alum Ni Bronze (AMS 4640) or CRES 15-5PH, AMS 5659, etc. The retainer wire for the stop segments may be made of CRES 300 series per ASTM A580, Inconel X-750 per AMS 5699, or the equivalent. 
     The T-locking rings and shims can be made of any suitable material, such as, for example stainless steel (15-5PH, AMS5659 or CRES 300 Series or equivalent). The bearings can be made of any suitable material, such as, for example plastic such as acetal resin engineering plastic (Delrin, L-P-392, KETRON PEEK-GF30, etc.) or low coefficient of friction and anti-galling metals (Alum Ni Bronze per AMS 4640, Nitronic 60 per AMS 5848, Cond A, Custom 455 per AMS 5617, etc.). The nuts can be made of any suitable material, such as, for example aluminum alloy coated with hard anodize/PTFE (or regular anodize) or stainless steel (15-5PH, AMS5659, CRES 300 Series, etc.) 
     The anti-rotation pins can be made of any suitable material, such as, for example stainless steel (CRES 15-5PH, AMS5659 or CRES 17-7PH, AMS 5678, etc.), the inner housing plug can be made of any suitable material, such as, for example aluminum alloy coated with hard anodize/PTFE, stainless steel (CRES 15-5PH, AMS 5659 or CRES 300 Series, etc.), or titanium alloy (GR 6AL-4V, AMS 4928, etc.), and the smalley retainer ring can be made of any suitable material, such as, for example stainless steel (CRES 300 series or an equivalent). 
     Although the invention has been shown and described with respect to a certain 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.