Patent Publication Number: US-7901240-B2

Title: Apparatus and method for electrical connector with flat cable adapter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority from U.S. Provisional Application 60/884,740 filed on Jan. 12, 2007. 
    
    
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to the field of electrical connectors and more particularly to electrical well head and submersible well pump connectors. 
     2. Background Information 
     Numerous applications involve the use of electrical connectors. High power connectors are used in applications including subsea connections, and in submersible pump connections in both water wells and oil wells. The size, weight, and orientation of the cables and connectors induce mechanical loads on connector components that make reliable mechanical and electrical connection difficult. In addition, the physical environment may include high temperature, high pressure, and abrasive and/or corrosive fluids, including liquids and gases. 
     The sealing of the electrical conductors in the connector from the surrounding fluids is crucial in such high power applications. 
     SUMMARY 
     In one aspect of the present invention, a submersible connector comprises an adapter housing coupled to a connector housing. An adapter insert has a first cavity formed therein. The first cavity is shaped to at least partially restrain motion in a first lateral axis of a flat cable placed therein. 
     In another aspect, an apparatus for connecting a flat cable to a submersible electrical connector comprises an adapter housing. An adapter insert has a first cavity shaped to at least partially restrain motion in a first lateral axis of a flat cable placed therein. An elastomer spring element is disposed in a second cavity in the adapter insert. The elastomer spring element imparts a squeeze on the flat cable at least partially restraining motion of the flat cable in a second lateral axis substantially orthogonal to the first lateral axis. 
     In yet another aspect, a method for connecting a flat cable to a submersible electrical connector comprises forming a first cavity in an adapter insert. The flat cable is placed in the first cavity to at least partially restrain motion in a first lateral axis of the flat cable. 
     Non-limiting examples of certain aspects of the invention have been summarized here rather broadly, in order that the detailed description thereof that follows may be better understood, and in order that the contributions they represent to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       For a detailed understanding of the present invention, references should be made to the following detailed description of the exemplary embodiment, taken in conjunction with the accompanying drawings, in which like elements have been given like numerals, wherein: 
         FIG. 1  shows an exploded view of a connector contact assembly according to one illustrative embodiment of the present invention; 
         FIG. 2  shows an assembled view of the elements of  FIG. 1 ; 
         FIG. 3  shows a portion of a contact receptacle according to one illustrative embodiment of the present invention; 
         FIG. 4A  shows an end view of a gripping contact according to one illustrative embodiment of the present invention; 
         FIG. 4B  shows a cross-section view along section line A-A of  FIG. 4A ; 
         FIG. 5  shows a non-limiting example of a portion of a connector assembly according to one illustrative embodiment of the present invention; 
         FIG. 6  shows a non-limiting example of a connector utilizing a contact assembly of one embodiment of the present invention to connect power to a submersible pump; 
         FIG. 7  is a sketch showing a seal element having a cable inserted through a passageway in the seal element; 
         FIG. 8A  is a cross section of the seal element of  FIG. 7 ; 
         FIG. 8B  is an end view of the seal element of  FIG. 7 ; 
         FIG. 8C  is an enlarged view of bubble A of  FIG. 8B ; 
         FIG. 9   a  is a sketch of a seal element having an insert; 
         FIG. 9B  is a sketch of the insert of  FIG. 9A ; 
         FIG. 10  is a sketch of a portion of a connector assembly for attaching flat cable to the connector; 
         FIG. 11A  is a sketch of one example of a flat cable adapter insert for the connector of  FIG. 10 ; 
         FIG. 11B  is a section view of the flat cable adapter insert of  FIG. 11A ; and 
         FIG. 12  shows an alternative embodiment of a flat cable adapter insert. 
     
    
    
     DETAILED DESCRIPTION 
     The following description presents non-limiting examples of embodiments of the present invention. Refer now to  FIGS. 1-4B .  FIG. 1  shows an exploded view of a connector contact assembly  5  according to one illustrative embodiment of the present invention. As shown in  FIG. 1 , a cable  40  has an electrical conductor  45  therein. Electrical conductor  45  may be a solid conductor, or, alternatively, a stranded conductor. 
     A gripping contact  15  has a cavity  16  sized to accept electrical conductor  45 . In one embodiment, the inner diameter of cavity  16  is a substantially a zero clearance fit with the outer diameter of electrical conductor  45 . Gripping contact  15  (see also  FIGS. 4A and 4B ) comprises a plurality of gripping fingers  20  with an outer surface  25  having a substantially conical shape. As seen in  FIG. 4B , the conical surface  25  is defined by angle β. In one embodiment, angle β is about 6°. Alternatively, angle β may be in the range of about 2° to about 10°. The internal surface  21  of fingers  20  substantially defines cavity  16 . While shown in  FIG. 4A  as comprising four fingers, any number of fingers may be used and are intended to be encompassed by the present disclosure. In one embodiment, the internal surface  21  of fingers  20  may be substantially smooth. Alternatively, in another embodiment, the internal surface  21  of fingers  20  may have a raised pattern (not shown) formed on surface  21 . Such a pattern may include, but is not limited to: a thread form, a tooth form, a knurling form, and any other raised pattern form used for gripping electrical conductor  45 . 
     On an opposite end of gripping contact  15 , an integral body  27  has an internally threaded bore  35 . Gripping contact  15  may be made out of an electrically conductive metal. Examples of such an electrically conductive metal include, but are not limited to: gold, silver, copper, copper alloys, aluminum, aluminum alloys, brass, bronze, and any other suitable electrically conducting metal. The surfaces  25  and  21  of fingers  20  may be plated with a suitable electrically conductive material to reduce galling and/or wear of the gripping fingers  20 . Any suitable plating may be used including, but not limited to: chrome plating, nickel plating, gold plating, and silver plating. 
     A contact receptacle  10  (see  FIGS. 1-3 ), has an internal conical surface  26  having an angle α where α≦β. In one embodiment, α is about 1.0° smaller than β. Alternatively, α may be smaller than β from about 0.5° to about 1.5°. The difference in angles ensures that fingers  20  of gripping contact  15  are forced to collapse around and compress electrical conductor  45 , as shown in  FIGS. 1 and 2 , when gripping contact  15  is urged axially into contact receptacle  10 . Contact receptacle  10  may be made from any of the materials as described previously for gripping contact  15 . Similarly, contact receptacle  10  may be plated by any of the platings discussed previously with respect to gripping contact  15 . 
     As shown in  FIGS. 1 and 2 , threaded element  30  engages threads  35  in gripping contact  15  and, under tension, reacts against shoulder  31  in contact receptacle  10  such that gripping contact  15  is axially urged into contact receptacle  10 . This motion causes interaction between outer surface  25  and inner surface  26  such that fingers  20  of gripping contact  15  are forced to collapse around and compress electrical conductor  45  along substantially the length of the extension of electrical conductor  45  into gripping contact  15 . The use of threaded element  30  provides a substantially repeatable force urging gripping contact  15  into contact receptacle  10 , thereby providing a repeatable holding force between electrical contact  45  and connector contact assembly. In addition, the substantially repeatable axial holding force provides a repeatable electrical contact between fingers  20  of gripping contact  15  and both electrical conductor  45  and contact receptacle  10 . Threaded element  30  may be a suitably sized threaded fastener that may be commercially available. Alternatively, threaded element  30  may be designed for this particular application using techniques known in the art. 
       FIG. 5  depicts a non-limiting example of a portion of a connector assembly  100  according to one illustrative embodiment of the present invention. Connector assembly  100  may be a power connector for use in connecting a power source to a submersible pump in a well. Alternatively, connector assembly  100  may be a sub-sea connector. As shown in  FIG. 5 , a multi-conductor armored cable assembly  41  has at least one insulated cable  40  with an internal electrical conductor  45 . Armored cable assembly  41  is connected to connector assembly  100  by cable adapter  101 . Crossover  102  connects cable adapter  101  to lower housing  103 . 
     It will be appreciated by one skilled in the art that the portion of connector assembly  100  shown in  FIG. 5  may be immersed in a high pressure fluid such as, for example, in a wellbore. To seal high pressure fluid from the internal electrical connections, cable  40  is inserted through seal  120 . Seal  120  is an elastomer seal that is compressed around the insulation of cable  40  to preclude passage of fluid toward the electrical contacts  15  and  10 . Seal  120  is held in place by follower  130 . Seal  120  may be made of a suitable elastomer. Suitable elastomers include but are not limited to, natural rubber, synthetic rubber, fluoroelastomers, perfluoroelastomers, ethylene propylene diene rubber (EPDM), and any other suitable elastomer. 
     Connector contact assembly  5  is inserted into an insulator  110  that is located above seal  120 . As shown, connector contact assembly  5  comprises gripping contact  15  assembled in contact receptacle  10  and held in place by threaded element  30 . To better facilitate field assembly, insulator  110  is located in lower housing  103  and upper housing  104  that are connected through coupling nut  140  and shoulder nut  135  acting against shoulder  145 . Insulator  110  may be a thermoplastic suitable for the particular environment encountered. Examples of such a thermoplastic include, but are not limited to, a polyetheretherketone material and a glass-filled polyetheretherketone material. Gripping contact  15  is in engaged contact, both mechanically and electrically with electrical conductor  45 . Connector assembly  5  conducts an electrical power signal to contact  105  which is electrically conducted to a surface power control system. One skilled in the art will appreciate that the connector assembly  5  and its components may be appropriately scaled to fit different size electrical conductors without undue experimentation. 
     One non-limiting example of an application of the present invention is shown in  FIG. 6 . In  FIG. 6 , a well  200  comprises a string of surface pipe  212  cemented in the upper portion of a bore hole  214  which extends into the earth to a location adjacent and usually below a subterranean oil productive formation (not shown). A wellhead  216  attaches to the surface pipe  212 . A set of slips  218  suspends a casing string  220  inside the bore hole  214  which is also cemented in place. A casing head  222  connects to the upper end of the casing string  220  and includes a tubing hanger  224 . 
     A tubing string  226  is suspended from the tubing hanger  224  and extends downwardly inside the casing string  220  to a location adjacent the productive formation. An electrically powered submersible pump  228 , of any suitable type, on the lower end of the tubing string  226  pumps oil or an oil-water mixture from the inside of the casing string  220  upwardly through the tubing string  226 . 
     Electric power is delivered to the downhole pump  228  through an armored cable  234  connected to a motor  236  comprising part of the submersible pump  228 . The cable  234  extends upwardly in the well  210  to a connector  100  of the present invention located immediately below the tubing hanger  224 . The connector  100  is secured to a mandrel or feed through socket  240  extending through the hanger  224 , seal assembly  230  and flange  232 . The connector  100  employs a contact assembly as described previously. In one embodiment, a pig tail connector  242  attaches the mandrel  240  to a power cable  244  extending to a source of power at the surface. 
     While described above as used in a submersible pump application, it is intended that the present invention encompass all applications requiring high electrical power transmission. Such applications include, but are not limited to: electrical motor connectors, transformer connectors, electrical generator connectors, welding machine connectors, and any other such electrical and/or electromagnetic devices. 
     In one illustrative embodiment,  FIGS. 7-8C  show elastomer seal element  120 , with cable  40  extending through an axial passage  211  in seal element  120 . Cable  40  has an insulating sheath  200  covering conductor  45 . Seal element  120  has a substantially cylindrical seal body  121  that fits closely in housing  103 . Seal element  120  also has an integral boot  211  extending outward from seal body  121 . Boot  211  is sized to receive cable  40 . As shown in  FIG. 8B , seal  120  may have multiple passages  211  for receiving multiple cables  40 . As discussed previously, seal  120  may be made of any suitable elastomer. Suitable elastomers include but are not limited to, natural rubber, synthetic rubber, fluoroelastomers, perfluoroelastomers, ethylene propylene diene rubber (EPDM), and any other suitable elastomer. It is intended that the present invention encompass any number of conductors that may be accommodated within a given housing geometry. 
     Boot  211  is exposed to the ambient fluid in the proximity of the installed connector  100  (see the preceding discussion relating to  FIGS. 5 and 6 ). Spaced apart along the internal surface of passage  211  is a plurality of sealing lips  220 . As seen in  FIGS. 7-8C , each sealing lip  220  has a recessed surface  222  adjacent thereto. Sealing lip  220  extends, in an undeformed state, a distance L above recessed surface  222 , where L is in the range of about 0.010 to about 0.030 inches. In one embodiment, sealing lip  220  has a substantially conical form in an undeformed state such that sealing lip  220  forms an angle θ with recessed surface  222 , where angle θ is in the range of about 5 to about 15 degrees. 
     In one non-limiting example, the sealing lips  220  have an initial compression against insulator  200  in the range of about 5-15%, thereby providing an initial fluid seal at the interface between sealing lip  220  and insulator  200 . As increasing external fluid pressure acts on the outer surface of boot  211 , the elastomer material of boot  211  is further compressed against insulator  200  of cable  40 . As the fluid pressure increases, boot  211  is increasingly compressed against insulator  200 . The increased compression causes sealing lip  220  to flatten out against insulator  200 , thereby increasing the sealing area as the fluid pressure is increased. The flattening of lip  220  also causes the edge of lip  220  to encroach into the cavity bounded by the insulator  200 , recessed surface  222 , and lip  220 . The same process occurs at each lip  220  along boot  210 . The plurality of seal lips  220  generates multiple redundant seals along boot  210  to prevent the incursion of contaminated fluid  202  along the interface between boot  210  and insulator  200 . 
       FIG. 7  also shows a conductor boot  212  extending axially toward the opposite direction from boot  210 . As shown in  FIG. 5 , conductor boot  212  fits into insulator  110  where conductor  45  is coupled to gripping contact  15 . As shown in  FIG. 4A , gripping contact  15  has several slotted fingers facing conductor boot  212 . When high fluid pressure P (see  FIG. 7 ), acts against surface  123  of seal  120 , seal  120  is forced axially in housing  103  (see  FIG. 5 ) such the end of conductor boot  212  may be extruded into the slots in gripping contact  15 . In one embodiment, an anti-extrusion washer  214  is attached to the end of conductor boot  212 . Anti-extrusion washer  214  is made of an insulating material such as, for example, an elastomer or a thermoplastic. Any suitable elastomer or thermoplastic having a suitable hardness to prevent extrusion under high pressure may be used. For example, elastomers having a Shore A durometer greater than 70 may be used. In one embodiment, washer  214  may be adhesively attached to the end of conductor boot  212 . Alternatively, washer  214  may be molded into the end of conductor boot  212  during manufacture of conductor boot  212 . 
     In another embodiment, see  FIG. 9 , seal  320  is similar in dimensions to previously described seal  120  and may be used interchangeably with seal  120  in connector  100 . Seal  320  has integral boot  211  molded on one side and an insert  321  molded into an opposite side. Insert  321  has at least one conductor boot  312  molded therein. Insert  321  may be of an elastomer material that is different than the elastomer material of seal  320 . In one example, the elastomer material of insert  321  may be an EPDM material having a Shore A hardness in the range of 70-80. The material of insert  321  is substantially harder than the material of the body  319  of seal  320 . The additional hardness acts to reduce extrusion of conductor boot  312  into the facing slots in gripping contact  15  as described previously. 
     Refer now to  FIGS. 10-11B .  FIG. 10  depicts a non-limiting example of a portion of a connector assembly  1000  according to one illustrative embodiment of the present invention. Connector assembly  1000  may be a submersible power connector for use in connecting a power source to a submersible pump in a well, similar to that of connector assembly  100  in  FIG. 5 . Connector assembly  1000  may also be used as a sub-sea connector. As shown in  FIG. 10 , a multi-conductor flat cable assembly  1041  has three insulated cables  40  with an internal electrical conductors  45 . As used herein, a flat cable is a cable wherein the electrical conductors lie in substantially the same plane. Flat cable assembly  1041  may have an outer armored layer  1044 . Flat cable assembly  1041  is connected to connector assembly  1000  by cable adapter  1020 . While shown with three cables  40 , it is intended that the present invention encompass any armored flat cable assembly having two or more cables  40 . In one illustrative example, insulated cables  40  may comprise electrical contact  45  with a surrounding insulating layer  1042 . In another example, an additional lead sheath layer  1043  may be placed around insulating layer  1042  to assist in preventing diffusion of well bore fluids into the insulating layer  1042 . Such diffusion may cause electrical leakage within the cable and cause substantial repair and replacement expense. 
     Cable adapter  1020  comprises adapter housing  1001  and adapter inserts  1002 . Each adapter insert  1002  has at least one cable retention cavity  1050  and at least one elastomer spring cavity  1055 . In one illustrative example, retention cavity  1050  is shaped to approximately fit the curved shape of the outer surface of flat cable assembly  1041  and to at least partially restrain the lateral motion of flat cable assembly  1041  in a first axis with relation to cable adapter  1020  during operation. As used herein, lateral motion indicates motion in an axis substantially orthogonal to the longitudinal axis of connector  1000 . While adapter inserts  1002  are shown as unattached elements, they may be connected together for example by a hinge on one side (not shown). 
     Elastomer spring element  1010  is placed in elastomer spring cavity  1055 . Elastomer spring element  1010  is sized to exert a predetermined range of squeeze on flat cable assembly  1041  when cable adapter  1020  is assembled with flat cable assembly  1041  as shown in  FIG. 10 . Elastomer spring element acts to at least partially restrain lateral motion of flat cable assembly  1041  in a second axis substantially orthogonal to the first axis of lateral motion, as well as longitudinal motion, during operation. Elastomer spring element  1010  may be any suitable elastomer including, but not limited to natural rubber, synthetic rubber, fluoroelastomers, perfluoroelastomers, ethylene propylene diene rubber (EPDM), and any other suitable elastomer. Squeeze in the assembled condition is in the range from about 5% to about 25%. Shore A hardness of the elastomer is in the range of about 60 to about 90. 
     In one example, electrical continuity may be maintained between cable outer armor layer  1044  and lower connector housing  102  through the use of set screws  1005 ,  1011  and  1012  providing electrical contact between insert  1002 , adapter housing  1001  and lower housing  102 , respectively. 
     In another alternative embodiment, see  FIG. 12 , adapter inserts  1102  having cable retention cavity  1150 . Retention cavity  1150  may be shaped to approximately fit the curved shape of the outer surface of flat cable assembly  1041  thereby at least partially restraining the lateral motion of flat cable assembly  1041 . Alternatively, retention cavity  1150  may be any suitable shape that acts to at least partially restrain the lateral motion of flat cable assembly  1041 . Such other shapes may be more economically manufacturable. 
     While the foregoing disclosure is directed to the non-limiting illustrative embodiments of the invention presented, various modifications will be apparent to those skilled in the art. It is intended that all variations within the scope of the appended claims be embraced by the foregoing disclosure.