Abstract:
A sensor array cable and method of construction thereof utilizing a sensor/interlink assembly to facilitate the relatively easy and inexpensive installation of a sensor device in a cable that includes a strength member to provide tensile strength to the cable, optical fibers or wires for carrying electrical or optical energy to and from the sensor device, and a protective outer jacket. A portion of the protective outer jacket is removed allowing access to the inner strength member and optical fibers. A segment of the strength member is removed and an interlink/sensor assembly is installed in its place. The interlink serves to maintain the tensile strength of the cable. Optical fibers and/or electrical wires are connected to the sensor device for operation. The interlink/sensor assembly and associated optical fibers and electrical wires are then enclosed in an overmold which is sealed to the outer protective jacket.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a sensor array cable and a method of making such cable. 
     The field to which the invention relates is that of cables including acoustic sensors of the kind most commonly used in marine seismic surveying. 
     BRIEF SUMMARY OF THE INVENTION 
     This invention provides a sensor array cable that incorporates a strength member, wires and/or optical fibers located around the strength member, a protective outer jacket, and one or more interlink/sensor assemblies. Such assemblies permit the easy and low cost installation of sensor devices in the cable. The methods of this invention include the steps of stripping off a portion of the protective outer jacket of such a cable, removing a portion of a strength member and inserting an interlink/sensor assembly in place of the removed portion. The cable is then overmolded with a plastic material. This method maintains the tensile strength, structural integrity and environmental ruggedness of the cable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top elevation view in cross section of a typical embodiment of a sensor array cable. 
     FIG. 2 is a perspective view in partial cross section of an interlink/sensor assembly. 
     FIG.  3 . is a perspective view of components of an embodiment of an interlink/sensor assembly. 
     FIG.  4 . is a side view in cross section of a portion of the cable of FIG. 1 between nodes 
     FIG.  5 . is a perspective view of a node on the cable of FIG. 1 showing the overmold. 
     FIG.  6 . is a perspective view of an interior portion of the protective jacket segment being removed from between nodes of the cable of FIG.  1 . 
     FIG.  7 . is a perspective view of a portion of the strength member segment being removed from between nodes of the cable of FIG.  1 . 
     FIG.  8 . is a perspective view of the free ends of the strength member segment with termini between nodes of the cable of FIG.  1 . 
     FIG.  9 . is a side elevation view in partial cross section of the strength member termination of the cable of FIG. 1 with a wedge termination. 
     FIG.  10 . is a side elevation view in partial cross section of the strength member termination of the cable of FIG. 1 with a cast termination. 
     FIG.  11 . is a side elevation view in partial cross section of the strength member termination of the cable of FIG. 1 with a braided splice termination. 
     FIG.  12 . is a side elevation view in partial cross section of the strength member termination of the cable of FIG. 1 with a knot termination. 
     FIG.  13 . is a side elevation view in partial cross section of the strength member termination of the cable of FIG. 1 with a capstan termination. 
     FIG.  14 . is a perspective view of the interlink being attached to the strength member segments of the cable of FIG.  1 . 
     FIG.  15 . is a side view in cross section of a clip being installed onto an interlink to capture a terminated strength member. 
     FIG.  16 . is a top elevation view of installed clips next to an interlink/sensor assembly. 
     FIG.  17 . is a top view in cross section of an installed interlink/sensor assembly encapsulated within an overmold. 
     FIG.  18 . is a perspective view of an installed interlink/sensor assembly and overmold in the cable of FIG.  1 . 
     FIG.  19 . is a perspective view of an installed interlink/sensor assembly where the interlink is internal to the sensor device. 
     FIG.  20 . is a side view of in cross section of a portion of the cable of FIG. 1 between nodes. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a sensor array cable  1  that includes interlink/sensor assemblies  5  at various locations along its length, denoted nodes  2 . 
     FIG. 2 illustrates components of an embodiment of interlink/sensor assembly  5  in partial cross section which comprises interlink  6  and sensor device  3  which when combined form interlink/sensor assembly  5 . 
     Interlink  6  allows sensor device  3  to be quickly and inexpensively installed into cable  1  while still maintaining the tensile strength of cable  1 . Interlink  6  is a structure preferably of appropriate shape and composition to evenly and continuously transmit mechanical stresses. Interlink  6  may be made of a plastic material such as engineering thermoplastic, or of a composite material such as glass reinforced epoxy, although this is not required and other suitable materials such as aluminum may be used as well, or a combination of materials may be used. In a preferred embodiment interlink  6  is internal to sensor device  3  as is illustrated in FIG.  19 . FIGS. 2 and 3 shows an alternative embodiment where interlink  6  is an external structure that contains sensor device  3 . 
     Sensor device  3  may include, as an example, any device that responds to a physical stimulus (for example heat, light, sound, pressure, magnetism or a particular motion) and transmits a resulting impulse (as for measurement or control). In one embodiment, for example, sensor device  3  is a hydrophone of the type commonly used in marine seismic surveying. Such hydrophones include but are not limited to those which operate using fiber optics or piezoelectric phenomena. Sensor device  3  may also include, as an example, any device for telemetry, signal conduction, signal processing, signal amplification, or the like. As such, sensor device  3  may contain, for example, optics and/or electronics for amplifying and/or transmitting output from a sensing device like a hydrophone. Sensor device  3 , when used to amplify optical signals, may contain a plurality of one or more optical fiber couplers, optical fiber delay coils, optical fiber splices, wavelength division multiplexer couplers and optical fiber doped with such atoms as erbium or ytterbium. Electronics for amplifying and multiplexing electrical signals may also be included in sensor device  3 . The precise function and configuration of sensor device  3  will vary with the application and does not affect the practice of the present invention. 
     FIG. 19 shows a preferred embodiment of interlink/sensor assembly  5  (as shown in FIG. 1) where interlink  6  is internal to sensor device  3 . In such an embodiment interlink  6  may be a machined or cast solid object, such as a rod, containing slots  14  for receiving termini of strength member segments  4 . Interlink  6  is then inserted into a cavity within sensor device  3  and bonded to sensor device  3 . Strength member segments  4  are subsequently attached, through termini, to interlink  6  at slots  14  by way of bonding with rigid adhesive such as glass filled epoxy or by set screws. 
     FIG. 3 shows the components of another embodiment of interlink/sensor assembly  5  (as shown in FIG. 1) where sensor device  3  is contained within interlink  6 . As illustrated, interlink  6  is a hollow body comprised of lower half  11  and upper half  12 . Upper half  12  is shown as, for example, a frame with a window  50 . Window  50  is an opening in upper half  12 . Either, or both, lower half  11  or upper half  12  may, or may not, contain window  50  to facilitate visual inspection/handling access during assembly of interlink/sensor assembly  5  and flooding with encapsulant when used. Lower half  11 , as shown, contains open cavity  13 , and slots  14  for receiving termini  17  for attachment to cable strength member segments  4 . Sensor device  3  is contained within hinged sleeve mount  15 . The combined hinged sleeve mount  15  and sensor device  3  is placed into open cavity  13  of lower half  11 . Hinged sleeve mount  15  protects enclosed sensor device  3  during handling. Upper half  12  is then placed over and attached to lower half  11 , resulting in the combination of interlink  6  with sensor device  3  by encapsulating sensor device  3  within interlink  6  to form interlink/sensor assembly  5  (as shown in FIG.  1 ). 
     The embodiments shown in FIGS. 19 and 3 are not intended to be exclusive. Other embodiments may be appropriate depending upon the particular application, including but not limited to, embodiments where the interlink is an integral part of a sensor device, such as being internal to the sensor device or an external appendage. 
     FIG. 4 shows an embodiment of sensor array cable  1  of FIG. 1, between nodes  2 , that facilitates the quick and inexpensive installation of interlink/sensor assembly  5 . Between nodes  2  cable  1  is comprised of a strength member segment  4  that bears mechanical stresses placed upon cable  1 , at least one transmission medium segment  7 , and a protective jacket segment  8  which protects the interior components of the cable. 
     Strength member segments  4  may be cord or braid made of metal or a synthetic material such as Aramid fibers or Vectran. As is common in the art strength member segments may also have an outer coating jacket. Strength member segments  4  are joined together at the nodes  2  by attachment to interlink/sensor assemblies  5 . 
     Transmission medium segments  7  may be electrical wires, optical fibers, or any other suitable energy wave guide or carrier which carries power and signals to and from sensor devices  3 . Segments  7  lie in close proximity to strength member segments  4  and in a preferred embodiment are wound helically around strength member segment  4  as shown, for example, in FIG.  20 . Transmission medium segments  7  are connected to sensor device  3  of interlink/sensor assembly  5  as necessary for its operation (receiving power, transmitting signals, etc.), or may pass through one or more nodes  2  without connection to a sensor device  3 . In such a situation, transmission medium segment  7  may be dressed onto interlink/sensor assembly  5 . 
     Protective jacket segments  8  may be made of any suitable material, but plastic material of sufficient elasticity, durability, strength and sealing ability such as polyethylene, polyurethane or nylon is preferred. 
     FIG. 5 illustrates how protective jacket segments  8  are connected together at nodes  2  through an overmold  9  which surrounds and contains interlink/sensor assembly  5 . 
     Overmold  9  is made of a material such as plastic, rubber or other suitable elastomer which seals and protects interlink/sensor assembly  5  and segments  7  from the environment and forms a seal with segments  8  on either side of node  2 . 
     Thus, the exterior of cable  1  includes protective jacket segments  8  joined together through overmolds  9 , to form a continuous sealed protection from an exterior environment, such as water. 
     Interlink/sensor assemblies  5  are easy to add to cable  1 . FIG. 6 shows the first step of installing an interlink/sensor assembly  5  into cable  1 . A middle portion  16  of protective jacket segment  8  between nodes  2  is removed, through stripping or otherwise, to expose the interior of cable  1  (including strength member segment  4  and transmission medium segments  7 ). This leaves a first protective jacket segment  18  and a second protective jacket segment  19  alongside the newly exposed cable interior. 
     FIG. 7 shows the second step of installing an additional sensor device. Exposed transmission medium segments  7  are manipulated to provide easy access to a predetermined length of exposed strength member segment  4 . If strength member segment  4  has an outer coating jacket then a portion of this outer coating jacket is removed by stripping or other means. An interior portion  22  of the strength member segment  4  is removed, which should be longer than interlink/sensor assembly  5  to be installed, leaving two exposed free ends  20  &amp;  21 , one on either end of the gap formed by removing interior portion  22 . 
     FIG. 8 shows the third step of installing an additional sensor device. Each exposed free end  20  &amp;  21  is given a terminus  17 . The termini  17  prevent ends  20  &amp;  21  from fraying, and allow for their attachment to interlink/sensor assembly  5  to transfer tensile loads from the strength member to interlink/sensor assembly  5 . Different configurations of terminus  17  are feasible and will vary with the type of strength member segment  4  used and connection mode to interlink/sensor assembly  5 . FIG. 8 shows an example of terminus  17  as ball swage (or right circular cylinder swage) where strength member segment  4  is steel cord or the like. 
     FIG. 9 shows wedge termination  23  which is another embodiment of terminus  17 . Strands  24  making up non-metallic strength member segment  4  are inserted and spread throughout conical volume  25  within termination block  26 . Metal wedges or cylinders  27  are driven into conical volume  25  between strands  24 . 
     FIG. 10 shows a cast rope termination  28  which is another embodiment of terminus  17 . Strands  24  of strength member segment  4 , which may be either metallic or synthetic cord or braid, are inserted and spread throughout conical volume  25  within termination block  26 . A hard casting material  29 , such as a glass-filled epoxy, is placed within conical volume  25  and effectively bonds strength member segment  4  to termination block  26 . 
     FIG. 11 shows a braided splice termination  30  which is another embodiment of terminus  17  when a braided synthetic cord, such as aramid, is used. A braided eye splice  31  is shown, the method and description of which is described in handbooks for sailing etc. such as  Chapman Piloting: Seamanship  &amp;  Small Boat Handling  (62 nd  Ed.) Elbert S. Maloney, Charles Frederic Chapman (September 1996) Hearst Books Publishing ISBN 0688 148921. 
     FIG. 12 shows a knot termination  32  which is another embodiment of terminus  17  when a synthetic cord is used. Any suitable knot  33  may be used in forming the termination, the method and description of which is described in handbooks for sailing etc. such as  Chapman Piloting: Seamanship  &amp;  Small Boat Handling  (62 nd  Ed.) Elbert S. Maloney, Charles Frederic Chapman (September 1996) Hearst Books Publishing ISBN 0688 148921. 
     FIG. 13 shows a friction creating capstan termination  34  which is another embodiment of terminus  17 . The free end of strength segment  8  is looped around capstan  35  preferably at least three times. Secure end  36  is then terminated by bonding end  36  to capstan  35 , or interlink to which capstan  35  is attached, or other means to prevent unraveling of the loop around capstan  35 . Other means of termination are also feasible and may be used as appropriate. 
     FIG. 14 shows the fourth step. Lower half  11  of interlink  6  with, as an example, slots  14  receives ends  20  &amp;  21  which are terminated with, for example, a ball swage  17 . Each end  20  &amp;  21  is inserted into a slot  14 . Termination link clamps  37  are then placed over slots  14  and attached to lower half  11  to hold terminated ends  20  &amp;  21  in place. Other means of attachment are also feasible and suitable depending upon the type of terminus employed, if any, e.g. swaged fitting, bonded connection, threaded crimp fitting, compression fitting, etc. 
     FIGS. 15 and 16 illustrates an embodiment where a clip  40  is installed onto interlink/sensor assembly  5  to capture terminus  17  in order to further assure a solid connection. 
     After attaching strength segment members  4  to interlink/sensor assembly  5 , the fifth step is to cut (if not already done) and connect the necessary transmission medium segments  7  (e.g. wires or optical cables) to sensor device  3 . For sensor devices  3  using optical components or fibers (such as a fiber optic hydrophone) optical fiber connectors such as FC/APC may be used, although the preferred method of optical fiber connection for such a sensor is fusion splicing. Other connection means will be appropriate depending upon the particular application. Any transmission medium segments  7  which are not connected to interlink/sensor assembly  5  may be dressed onto interlink/sensor assembly  5 . 
     FIG. 17 shows overmold  9 , the result of the sixth and final step of installing a sensor into cable  1 . After installing interlink/sensor assembly  5  as described above, the exposed cable interior with the interlink/sensor assembly  5  is then overmolded with a protective material such as plastic, rubber or another suitable elastomer, so that overmold  9  is formed and a watertight seal is made with protective jacket segments  8  on either side of the exposed cable interior. Overmold  9  may be formed by injection molding, casting or otherwise. It is also feasible, before forming the overmold to surround and contain said interlink/sensor assembly within a rigid tube. This provides the advantages of more flexibility in implementing molding/curing processes. Furthermore, if a rigid tube is employed which extends over the protective jacket segments it may simply be filled with an encapsulant and thus itself serve as an overmold. 
     FIG. 18 shows a perspective view in cross section of a completed node  2  on cable  1  containing an interlink/sensor assembly  5  and overmold  9 . 
     This method for installing a sensor device into a cable may be used to make an entire sensor array cable  1 , starting with a cable containing a strength member  4 , one or more transmission mediums  7 , and a protective jacket  8 , then adding the desired number of interlink/sensor assemblies  5 . This method permits including any number of interlink/sensor assemblies to form sensor array cable  1 . 
     Glossary of Terms 
     What follows is a glossary of terms to aid in the understanding of the disclosure and claims. 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                 Node - 
                 A location on a sensor array cable where a sensor 
               
               
                   
                 device or an interlink/sensor assembly is located. 
               
               
                 Cord - 
                 A long slender flexible material which may consist 
               
               
                   
                 of several strands woven or twisted together. 
               
               
                 Fiber - 
                 A slender and elongated natural or synthetic 
               
               
                   
                 filament, which may be constructed of a material, 
               
               
                   
                 such as glass or metal, which can convey (carry) 
               
               
                   
                 electrical or light energy. 
               
               
                 Braid - 
                 A cord having at least two component strands 
               
               
                   
                 forming a regular diagonal pattern down its length. 
               
               
                 Strength member 
                 A cord made of a material, such as metal or Aramid 
               
               
                 segment- 
                 fibers, that lies between nodes and provides tensile 
               
               
                   
                 strength to a sensor array cable. 
               
               
                 Interlink - 
                 An object of a particular shape and composition 
               
               
                   
                 adapted to transmit and bear mechanical stresses. 
               
               
                 Sensor device- 
                 A device that responds to a physical stimulus (for 
               
               
                   
                 example heat, light, sound, pressure, magnetism or 
               
               
                   
                 a particular motion) and transmits a resulting 
               
               
                   
                 impulse (as for measurement or control), or a 
               
               
                   
                 device for telemetry, signal conduction, signal 
               
               
                   
                 processing, signal amplification, or the like. 
               
               
                 Interlink/sensor 
                 A combination of a sensor device and an interlink. 
               
               
                 assembly - 
               
               
                 Transmission 
                 An object of a fixed length made of a material 
               
               
                 medium segment - 
                 which can carry power and energy signals to and 
               
               
                   
                 from a sensor device, and which may include, for 
               
               
                   
                 example, electrical wires or optical fibers. 
               
               
                 Protective 
                 An object made of a material, such as plastic, 
               
               
                 jacket segment - 
                 rubber or other elastomer which protects a strength 
               
               
                   
                 member segment, a transmission medium segment, 
               
               
                   
                 or both, from the surrounding environment, such as 
               
               
                   
                 water. 
               
               
                 Overmold - 
                 An object made of a material, such as plastic, 
               
               
                   
                 rubber, or other elastomer which surrounds and 
               
               
                   
                 contains an interlink/sensor assembly and 
               
               
                   
                 transmission medium segments at a node, and forms 
               
               
                   
                 a watertight seal with the protective jacket 
               
               
                   
                 segments on either side of the node. 
               
               
                 Terminus 
                 An end of a cord, fiber, or wire which has been 
               
               
                 (plural: Termini) - 
                 shaped, or treated mechanically, chemically, or 
               
               
                   
                 otherwise to prevent fraying and which allows 
               
               
                   
                 attachment to a interlink and transmission of tensile 
               
               
                   
                 loads. 
               
               
                 Electrical wiring - 
                 A conductor of electricity. 
               
               
                 Optical fiber - 
                 A fiber that conveys (carries) light energy. 
               
               
                 Plastic - 
                 An elastomer, rubber, or any of numerous organic 
               
               
                   
                 synthetic or processed materials that are mostly 
               
               
                   
                 thermoplastic or thermosetting polymers of high 
               
               
                   
                 molecular weight and that can be molded, cast, 
               
               
                   
                 extruded, drawn, or laminated into objects, films, or 
               
               
                   
                 filaments. 
               
               
                 Injection molding - 
                 A method of creating plastic objects, films, or 
               
               
                   
                 filaments. 
               
               
                 Attachment point - 
                 A location on an interlink/sensor assembly where a 
               
               
                   
                 strength segment may be attached, such as a groove 
               
               
                   
                 for accepting a terminus. 
               
               
                 Dressed - 
                 The placement of a transmission medium segment 
               
               
                   
                 in and/or over and/or around an interlink/sensor 
               
               
                   
                 assembly. 
               
               
                 Connector - 
                 A device that joins or links a transmission medium 
               
               
                   
                 segment and a sensor device so that electrical or 
               
               
                   
                 light energy can pass between them. 
               
               
                 Telemetry module - 
                 Any device used to receive an electrical or optical 
               
               
                   
                 signal and to transmit the signal with, or without, 
               
               
                   
                 amplification or modification. 
               
               
                 Combine - 
                 To bring two or more objects into close 
               
               
                   
                 relationship, such as physical contact, without 
               
               
                   
                 necessarily permanently or removably attaching the 
               
               
                   
                 objects. 
               
               
                 Occupy - 
                 To fill, at least partially, a volume of space within a 
               
               
                   
                 cavity. 
               
               
                 Cavity - 
                 An unfilled space within an object. 
               
               
                 Open Cavity - 
                 An unfilled space within an object that is 
               
               
                   
                 contiguous with the space surrounding the object. 
               
               
                 Closed Cavity - 
                 An unfilled space within an object that is not in 
               
               
                   
                 contact with the space surrounding the object. 
               
               
                 Encapsulant - 
                 A material used to encapsulate an object, such as 
               
               
                   
                 an interlink/sensor assembly, which serves to 
               
               
                   
                 protect the object encapsulated from mechanical 
               
               
                   
                 stresses or loads or environmental conditions (such 
               
               
                   
                 as water or air), and in some circumstances is used 
               
               
                   
                 to facilitate or enhance performance of a device by, 
               
               
                   
                 for example, matching the acoustic impedance of 
               
               
                   
                 the surrounding environment. An encapsulant may 
               
               
                   
                 be any suitable material including, but not limited 
               
               
                   
                 to, polyurethane, polyethylene or other elastomer. 
               
               
                 Encapsulate - 
                 To completely enclose in. 
               
               
                 Outer Coating 
                 An object made of a material, such as plastic, 
               
               
                 Jacket - 
                 rubber or other elastomer which coats and protects 
               
               
                   
                 a strength member segment.