Abstract:
A multi-gimbal configured transition protectively interfaces a mooring and communication cable to a communication ocean buoy. The transition interface contains a segmented, flexible sheath formed of a plurality of pivotally interconnected gimbal rings having mutually adjacent interior apertures through which one or more communication link members pass. Successive gimbal rings are orthogonally pivotally interconnected with one another so as to make the flexible sheath flexible in three dimensions. Upper ends of one or more communication link members are connectable with a communication cable connection fixture of the buoy. Lower ends of the communication link members are connectable to communication cable terminal connectors of a terminal end of the mooring cable.

Description:
FIELD OF THE INVENTION 
   The present invention relates in general to communication systems, subsystems and components therefor, and is particularly directed to a new and improved multi-gimbal configured transition for securely and protectively interfacing a mooring and communication cable to a communication ocean buoy. 
   BACKGROUND OF THE INVENTION 
   Ocean-deployed communication buoys, a reduced complexity depiction of one of which is shown in  FIG. 1 , are constantly being subjected to very dynamic forces that have made the integrity of the cable transition interface  10  between the keel  21  of the buoy  20  and a relatively static mooring/communication cable  30  an ongoing problem. Specifically, the substantially continuous (roll, pitch and yaw) motion of the buoy impart forces that act on the cable transition interface in three-dimensions and which, over time, introduce mechanical fatigue at cable and the transition interface. As a consequence, unless the transition interface between the cable and the buoy is both structurally robust and relatively flexible, it can be expected that the mooring attachment  10  with the cable  30  will eventually fail as a result of millions of motion cycles to which the buoy is subjected. 
   As diagrammatically illustrated in  FIG. 2 , in an attempt to reduce or ameliorate this problem, currently employed buoy/cable transition interface designs segregate or break out the communication cable interface proper  30  from the mooring cable&#39;s attachment interface  40  that is supported by the buoy keel  21 . Although the mechanical attachment interface  40  (shown as a dual swivel joint arrangement) accommodates the pitching and rolling motion of the buoy  20  relative to the mooring/communication cable  30 , such a cable interface design unfortunately places the most fragile components of the communication cable interface, shown as a pair of optical fiber cable segments  31  and  32  in  FIG. 2 , outside of the relatively static mooring cable, exposing them to substantial dynamic forces at the ocean surface. Moreover, in their segregated condition, the transition cable segments  31  and  32  take on a configuration that allows them to become entangled with floating sea vegetation and flotsam, fishing/trawler lines/nets, and being subjected to snagging and chafing on the interface mechanism itself. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, drawbacks of conventional ocean buoy mooring/communication cable transition interfaces, including those discussed above, are effectively obviated by a multi-gimbal configured buoy-cable transition interface, that is configured to decouple relative motion between the buoy and the communication cable on the one hand, and to also provide a structurally robust protective sleeve or sheath structure for the terminal end portion of the communication cable at its exit interface with the mooring cable. 
   To this end, the multi-gimbal configured buoy-cable interface of the invention comprises a segmented, flexible sheath that is formed of a plurality of double-pivotally interconnected gimbal rings, having mutually adjacent interior apertures through which pass one or more communication link members, such as lengths of electrical or fiber optic communication cable that provide the communication transition between the riser end of the cable and associated terminations at the keel of the buoy. Each of the pivotally interconnected gimbal rings has a dual orthogonal pivoting interface with adjacent gimbal rings on opposite ends thereof, which makes the protective sheath flexible in three dimensions, and thereby accommodates the forces that act on the buoy, so as to mitigate against mechanical fatigue at both the terminal end of the cable and the transition interface. 
   A respective gimbal ring contains a first, relatively large diameter gimbal ring portion, and a second, relatively small diameter gimbal ring portion that is sized to fit within the first gimbal ring portion of an adjacent gimbal ring. The first gimbal ring portion includes a first pair of pivot apertures, and the second gimbal ring portion includes a second pair of pivot apertures having an axis orthogonal to that of the first pair of pivot apertures, and which are sized to be alignable with a first pair of pivot apertures of an adjacent gimbal ring when the second gimbal ring portion of one gimbal ring is inserted into the first gimbal ring portion of an adjacent gimbal ring. Respective pairs of pivot pins are inserted through aligned first and second pairs of pivot apertures of adjacent gimbal rings, so as to pivotally interconnect adjacent gimbal rings. 
   The outer surface of a generally cylindrically shaped wall of a relatively small diameter gimbal ring is tapered so as to form a pair of sloped wall regions. These sloped regions provide clearance so the rings can pivot and also keep the passageway open for the cable to pass. These sloped wall regions allow for pivotal movement of adjacent gimbal elements, and thereby the intended flexibility of the cable protecting structure which the multi-gimbal configured buoy-cable interface of the invention provides. An exterior surface of the first gimbal ring portion is provided with stop elements which limit the extent to which the second gimbal ring portion of an adjacent gimbal ring may pivot. 
   Attachment of the multi-gimbal configured sheath structure to the keel of a buoy is provided by way of an buoy attachment gimbal base that is affixed to the communication cable connection fixture of the buoy, and contains a relatively small diameter gimbal ring portion that is sized to fit within the relatively large diameter gimbal ring portion of the uppermost end one of the pivotally interconnected gimbal rings of the flexible sheath. In a complementary manner, attachment of the multi-gimbal configured sheath structure to the riser end of the communication/mooring cable is provided by way of a riser attachment gimbal ring, that contains a relatively large diameter gimbal ring portion sized to receive a relatively small diameter gimbal ring portion of the lowermost end one of the pivotally interconnected gimbal rings of the flexible sheath. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a reduced complexity illustration of an ocean-deployed communication buoy; 
       FIG. 2  diagrammatically illustrates a conventional buoy/cable transition interface which breaks out communication cable segments from the mooring cable&#39;s attachment; 
       FIG. 3  is a diagrammatic perspective view of a ‘flexed’ condition of the multi-gimbal configured buoy-cable interface of the present invention; 
       FIG. 4  is a diagrammatic perspective view of an ‘in-line’ condition of the multi-gimbal configured buoy-cable interface of the present invention; 
       FIG. 5  is a diagrammatic perspective view of an attachment gimbal base portion of the multi-gimbal configured buoy-cable interface of  FIGS. 3 and 4 ; 
       FIG. 6  is a diagrammatic perspective view of a dual axis pivotal gimbal ring of the multi-gimbal configured buoy-cable interface of  FIGS. 3 and 4 ; 
       FIG. 7  is a diagrammatic perspective view of a cable riser attachment portion of the multi-gimbal configured buoy-cable interface of  FIGS. 3 and 4 ; 
       FIGS. 8 and 9  are respective diagrammatic perspective ‘transparent’ views of flexed and in-line conditions of the multi-gimbal configured buoy-cable interface of the present invention; and 
       FIG. 10  is a diagrammatically side view illustrating the range of motion of the communication cable transition interface of the present invention. 
   

   DETAILED DESCRIPTION 
   Attention is now directed to  FIGS. 3 and 4 , which show respective flexed and in-line assembled views of the multi-gimbal configured buoy-cable interface in accordance with the present invention, as well as  FIGS. 5 ,  6  and  7 , which illustrate in perspective a buoy attachment gimbal base, a middle gimbal ring, and a cable riser attachment lower gimbal ring, of which the multi-gimbal configured buoy-cable interface shown in  FIGS. 3 and 4  is formed. All of the components are preferably made of a structurally rigid and rugged material such as steel. As shown in the assembled views of  FIGS. 3 and 4 , the multi-gimballed, flexible sheath structure of the invention comprises a cascaded interconnection of a single buoy attachment gimbal base  500 , a plurality (five in the illustrated example) of middle gimbal rings  600 , and a single cable riser attachment lower gimbal ring  700 . 
   As described briefly above, attachment of the multi-gimbal configured sheath structure of the present invention to the keel of a buoy is provided by way of an buoy attachment gimbal base  500  that is affixed to the communication cable connection fixture of the buoy, and contains a gimbal ring that is sized to fit within the relatively large diameter gimbal ring portion of the uppermost end one of the pivotally interconnected gimbal rings of the flexible sheath. 
   More particularly, as shown in detail in the perspective view of  FIG. 5 , the buoy attachment gimbal base  500  is comprised of a generally circular mounting plate  501 . A generally circular aperture  503  is formed in the center of the plate  501 , while a plurality of bolt attachment bores  505  for attaching the gimbal base  500  to a fixture retained on the keel of the buoy are distributed around the perimeter of the plate  501 . Surrounding and substantially flush with the interior edge of the aperture  503  is a generally cylindrical gimbal ring support  507 , which extends between the mounting plate  501  and a reducing ring  509 , mounted atop the gimbal ring support. 
   Formed in the generally cylindrical sidewall  509  of the gimbal ring support  507  are a plurality (e.g., four in the present example) of diver-access apertures  511 , that are sized to provide a diver ready access to the communication cable interface adjoining the buoy keel. Between the apertures  511  are generally triangular gussets  513  which are welded to the exterior sidewall  509  of the of the gimbal ring support  507  and to the bottom surface  515  of the mounting plate  501 . Affixed to the reducing ring  509  is a generally cylindrically shaped, relatively small diameter gimbal ring  520  which, as noted above, is sized to fit within the relatively large diameter gimbal ring portion of the uppermost end one of the pivotally interconnected gimbal rings of the flexible sheath. 
   The gimbal ring  520  has an interior sidewall  522  that is generally flush with the interior edge of a generally circular hole formed in the reducing ring  509 . The outer surface of the generally cylindrically shaped wall of the gimbal ring  520  is tapered so as to form a pair of sloped wall regions  541  and  542  at a distal end of the ring. As described previously shown in  FIG. 3 , these sloped wall regions allow for pivotal movement of adjacent gimbal elements, and thereby the intended flexibility of the cable protecting structure which the multi-gimbal configured buoy-cable interface of the invention provides. 
   A pair of gimbal ring pivot pin retention tubes  524  and  526  are formed in diametrically opposed sidewall regions of the gimbal ring  520 . These pivot pin retention tubes are sized to receive respective pairs of pivot pins, such as those shown at  528  and  529 , which passes through pivot pin bores  534  and  536  in the respective tubes  524  and  526  as well as associated pivot tube bores  602  and  604  in the middle gimbal ring  600  shown in FIG.  6 . As shown in  FIGS. 3 and 4 , the gimbal base  300  is also provided with sacrificial zinc anodes  545  for corrosion mitigation. 
   The configuration of a respective middle gimbal ring  60  is shown in perspective in  FIG. 6  as comprising a lower, relatively small diameter, generally cylindrical gimbal ring section  610 , the distal end  612  of which is tapered so as to form a pair of sloped wall regions  614  and  616 , to provide for pivotal movement of adjacent gimbal elements. As mentioned previously, the slope of the wall regions is defined so as to provide clearance, so that the rings can pivot and also keep the passageway open for the cable to pass. 
   A pair of gimbal ring pivot pin retention tubes  624  and  626  are formed in diametrically opposed sidewall regions of the gimbal ring section  610 . As in the case of the buoy attachment gimbal base, the pivot pin retention tubes  624  and  626  are sized to pivot pins, shown at  628  and  629 , which pass through pivot pin bores  634  and  636  in the respective tubes  624  and  626  as well as associated pivot tube bores  602  and  604  of another gimbal ring. 
   The lower, relatively smaller diameter, generally cylindrical gimbal ring section  610  abuts against one side of a reducing ring  630 , on the opposite side of which is situated an upper, generally cylindrical and relatively larger diameter gimbal ring section  640 . A pair of gussets  633 ,  635  are formed between the interior wall surface of the upper gimbal ring section  640  and the reducing ring  630 . Like the lower gimbal ring section  610 , the upper gimbal ring section  640  has a distal end  642  thereof tapered so as to form a pair of sloped wall regions  644  and  646 , that allow for pivotal movement of adjacent gimbal elements. 
   However, the sloped wall regions  644  and  646  are generally orthogonal to the sloped wall regions  614  and  616  of the lower gimbal ring section, so as to provide alternating directions of pivot axes between adjacent gimbal ring elements. This dual pivotability of a respective gimbal ring provides the gimbal jointed sheath with flexibility in three dimensions. As noted earlier this enables the protective sheath of the invention to accommodate forces that act on the buoy, so as to mitigate against mechanical fatigue at both the terminal end of the cable and the transition interface. 
   The interior diameter of the upper gimbal ring section  640  is larger than that of the lower gimbal ring section  610  so as to accommodate pivotal engagement with the lower gimbal ring section of an adjacent gimbal ring. A pair of gimbal ring pivot pin retention tubes  624  and  626  are formed in diametrically opposed sidewall regions of the lower gimbal ring section  610 , while a pair of gimbal ring pivot pin retention tubes  652  and  654  through which tube bores  602  and  604  respectively pass, are formed in diametrically opposed sidewall regions of the upper gimbal ring section  640 . 
   The axes of the tube bores  602  and  604  in the upper gimbal ring section  640  are mutually orthogonal to those of tube bores  634  and  636  in the lower gimbal ring section, so as to provide alternating pivot axes between adjacent gimbal ring elements, as described above. As in the case of the buoy attachment gimbal base, the pivot pin retention tubes  624  and  626  of the lower gimbal ring section are sized to receive a pivot pin shown at  628  which passes through pivot pin bores  634  and  636  in the respective tubes  624  and  626  as well as associated pivot tube bores  602  and  604  another gimbal ring. 
   In addition to the tubes  652  and  654 , which are axially orthogonal to the tubes  624  and  626  in the lower gimbal ring section, the exterior cylindrical wall surface  662  of the upper gimbal ring section  640  is provided with a pair of tapered stops  664  and  666 . These stops are orthogonal with tubes  652  and  654  and serve to limit the range of pivotal motion of adjacent gimbal ring sections. As further shown in  FIGS. 3 and 4 , the relatively larger diameter gimbal ring sections  640  are provided with sacrificial zinc anodes  645  for corrosion mitigation. 
   The configuration of the cable riser attachment, lower gimbal ring is diagrammatically illustrated in  FIG. 7  as comprising a generally flat, circular mounting ring which, like the mounting plate  501  of the mounting base of  FIG. 5 , has a plurality of bolt attachment bores  703  for attaching the lower gimbal ring to an associated generally tapered riser attachment bracket of conventional construction, and shown at  705  in  FIGS. 3 and 4 . Radially and interiorly offset from the circular circumference  707  of mounting ring  701  is a generally cylindrical gimbal ring  711  having a distribution of diver-access apertures  713  in the cylindrical sidewall thereof. A plurality of stiffening flanges  715  are welded to the outer cylindrical surface of the gimbal ring  711  and to the circular mounting ring  701 . The stiffening flanges  715  and the gimbal ring  711  terminate at the bottom side of a reducing ring  721 . Mounted to the top of the reducing ring  721  is an upper, generally cylindrical and relatively larger diameter gimbal ring section  723 , which is configured the same as the upper gimbal ring section  640  of the middle gimbal ring  600  shown in FIG.  6 . 
   Namely, the upper gimbal ring section  723  of the cable riser attachment lower gimbal ring has a distal end  725  that is tapered so as to form a pair of sloped wall regions  727  and  729 , so as to allow for pivotal movement of an adjacent middle gimbal element. Moreover, the interior diameter of the upper gimbal ring section  723  is larger than that of the lower gimbal ring section  610  of a middle gimbal ring, so as to accommodate pivotal engagement with the lower gimbal ring section of an adjacent middle gimbal ring. 
   A pair of gimbal ring pivot pin retention tubes  731  and  733  are formed in diametrically opposed sidewall regions of the upper gimbal ring section  723 . As in the case of the buoy attachment gimbal base, the pivot pin retention tubes  731  and  733  are sized to receive pivot pins  737  and  738 , respectively, which pass through pivot pin bores  741  and  743  in the respective tubes  731  and  733 , as well as associated pivot tube bores  634  and  636  of a middle gimbal ring. Also, the exterior cylindrical wall surface  751  of the upper gimbal ring section  723  is provided with a pair of stops  753  and  755 , that serve to limit the range of pivotal motion of an adjacent gimbal ring section. In order to mitigate against corrosion, opposite sides of the relatively larger diameter gimbal ring section  723  is provided with sacrificial zinc anodes, one of which is shown at  745  in  FIGS. 3 and 4 . 
   The manner in which the multi-gimbal jointed protective sheath of the present invention allows for flexing of its interior communication cable to accommodate changes in attitude of the buoy keel relative to the cable riser is diagrammatically illustrated in the ‘transparent’ views of  FIGS. 8 and 9 . As shown therein, at respective cable connector joints  810 ,  820  at opposite ends of the transition interface, the interior communication cable sections  830  and  840  are retained in a relatively linear attitude with respect to associated connection terminals in the buoy keel and riser fixtures. However, between these two extremes the cable is allowed to flex or bend, but only to the extent allowed by the gimbals of the multi-gimbal jointed sheath. As pointed out above, the degree of bend is defined by the slope of the wall regions of the two gimbal portions of adjacent gimbals and their adjacent stops. 
   It will be readily understood by one skilled in the art that the extent to which the communication cable may be bent is further defined by the number of gimbals segments of which the sheath is comprised. For a given size and slope angle of each of the relatively larger and relatively smaller diameter portions of a gimbal ring, increasing the number of gimbal rings that are pivotally interconnected to form the communication interface transition provides a proportional increase in the overall amount of bend of the interior cable, as diagrammatically illustrated in FIG.  10 . Still within the interior of the sheath the bend radius remains the same since the bending radius of any two adjoining gimbal rings is not changed by the number of gimbal rings. 
   While I have shown and described an embodiment in accordance with the present invention, it is to be understood that the same is not limited thereto but is susceptible to numerous changes and modifications as known to a person skilled in the art. I therefore do not wish to be limited to the details shown and described herein, but intend to cover all such changes and modifications as are obvious to one of ordinary skill in the art.