Abstract:
A fiber optic shield connector and enclosure are adapted to provide reliable, weather resistant ground connections to the conductive shield of a fiber optic cable. The connector comprises two steel clamp sections which form a rigid, conductive assembly surrounding the fiber optic cable. A plurality of sharpened, hollow grounding screws thread through the clamp sections to pierce the cable jacket and establish electrical contact with the cable shield. A gel-filled, two-part molded plastic enclosure surrounds the assembled cable and connector to provide protection from the environment.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to devices for implementing a ground connection between a metallic shield of a cable and a common ground point. More particularly, the present invention relates to clamp devices which mount to fiber optic cables and implement a ground connection via a flexible conductor. 
     Fiber optic cables are generally buried under ground and typically constructed in a tubular fashion with numerous fiber optic conductors surrounded by a conductive ground shield which is in turn surrounded by a protective jacket of tough flexible plastic or rubber. Many fiber optic cables also include steel cords running the length of the cable, positioned between the conductive shield and the protective jacket, which protect the fragile inner conductors and reinforce the cable. To function properly and safely, cable shields must be grounded at spaced ground points established by regulation and/or operational specifications and practices. 
     Cable shield ground clamp assemblies are ordinarily positioned within a cabinet, housing or other enclosure to provide a common ground point and shelter for the cables and attached grounding assemblies. Such enclosures are frequently located outdoors and/or underground, where the enclosures and their contents are subjected to intense environmental changes. It is not uncommon for the enclosure to be exposed to moisture in the form of rain, ground water or condensation. Temperature swings from well below freezing to above 100° F. are not uncommon. 
     Establishing reliable electrical connections between the conductive shield of fiber optic cables and a common ground point presents difficulties well known in the art. Conventionally, craft personnel must cut through the protective jacket and expose the metallic shield prior to affixing any clamp or other device for establishing a ground path. Any such cutting or piercing of the protective shield by craft personnel makes the fiber optic conductors and linear strength members susceptible to being damaged, weakened or cut with the potential for delays and costly repairs. Costs are further increased by the specialized training and equipment required to prepare craft personnel to perform the task of cutting the cable shield. 
     SUMMARY OF THE INVENTION 
     Briefly stated, the invention in a preferred form is a fiber optic shield connector for establishing a reliable ground path from the conductive shield of a fiber optic cable to a common ground point via a flexible conductor. A preferred form of the fiber optic shield connector includes cooperative clamp sections, each composed of electrically conductive, structurally rigid material. Each clamp section includes an open-ended trough defining a longitudinal channel with open, semicircular ends. Linear flanges integrally extend transversely from the trough and contain structures for receiving hardware which joins the two clamp pieces together in a conductive, rigid structure surrounding an open-ended receiving cavity. The structure forming the trough of each clamp section has several threaded openings for receiving grounding screws. Grounding screws threadably engage the threaded openings and penetrate through the clamp material, projecting into the receiving cavity formed by the clamp. Each grounding screw is provided with a sharpened cutting tip surrounding a deep axial recess in the center of the screw. 
     The clamp is assembled around a fiber optic cable, forming a conductive rigid enclosure with the cable traversing therethrough. The grounding screws are then tightened, penetrating the cable jacket and contacting the conductive shield. The cutting tips penetrate the jacket by cutting a small core of jacket material which is allowed to pass into the deep axial recess of each grounding screw. Several grounding screws are angularly and longitudinally positioned in each clamp section to increase the number and quality of ground contacts with the cable shield. A flexible ground lead is affixed to the clamp and connected to the common ground point. 
     In another embodiment of the invention, the assembly including the fiber optic cable, shield connector and ground lead is then placed within a molded two piece enclosure. The enclosure includes a box-like tub and mating box-like cover, each surrounding a substantially rectangular interior space with rounded bifurcated notches disposed in the end walls of both the cover and the tub. The notches are aligned so the assembled enclosure has a longitudinal opening which allows the cable to pass through the enclosure. The tub and cover interior spaces may be partially filled with water repellant gel. A durable waterproof enclosure surrounding the ground connection is formed by the mated cover and tub. 
     An object of the invention is to provide a new and improved connector for establishing and maintaining a high quality ground connection with a fiber optic cable shield. 
     Another object of the invention is to provide a new and improved fiber optic shield connector which does not require opening of the cable shield prior to installation of the connector. 
     A further object of the invention is to provide a new and improved fiber optic shield connector that minimizes damage to the fiber optic cable jacket while establishing reliable grounding of the fiber optic cable shield. 
     A yet further object of the invention is to provide a new and improved fiber optic shield connector which reduces labor costs and craft error. 
     A yet further object of the invention is to provide a new and improved fiber optic shield connector assembly having improved water, weather and environmental resisting capabilities. 
     Other objects and advantages of the invention will become apparent from the specification and the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially exploded perspective view of a fiber optic shield connector in accordance with the present invention; 
     FIG. 2 is a top view of a grounding screw of the connector of FIG. 1; 
     FIG. 3 is a perspective side view of the grounding screw of FIG. 2; 
     FIG. 4 is a bottom view of the grounding screw of FIG. 2; 
     FIG. 5 is a perspective view of the fiber optic shield connector of FIG. 1 installed on a fiber optic cable (partially illustrated) with a ground lead (partially illustrated) in accordance with an aspect of the present invention; 
     FIG. 6 is a partially exploded perspective view of a fiber optic shield connector enclosure in accordance with an aspect of the present invention as seen from below; 
     FIG. 7 is a partially exploded perspective view of the fiber optic shield connector enclosure of FIG. 6 as seen from above; 
     FIG. 8 is a top plan view of the cover of the fiber optic cable shield connector enclosure of FIG. 6 as seen from above; 
     FIG. 9 is a bottom plan view of the fiber optic shield connector cover of FIG. 8; 
     FIG. 10 is an end view, partly in schematic, of the fiber optic shield connector cover of FIG. 8; 
     FIG. 11 is a bottom view of the tub of the fiber optic cable shield connector enclosure of FIG. 6; 
     FIG. 12 is a top plan view of the fiber optic cable shield connector tub of FIG. 11; 
     FIG. 13 is an end view, partly in schematic, of the fiber optic cable shield connector enclosure tub of FIG. 11; and 
     FIG. 14 is a partially exploded perspective view of the fiber optic shield connector/fiber optic cable/ground lead assembly of FIG. 5 in functional conjunction with the enclosure of FIG.  7 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference to the drawings wherein like numerals represent like parts throughout the Figures, a fiber optic shield connector in accordance with the present invention is generally designated by the numeral  10 . Fiber optic shield connector  10  is particularly adapted for establishing a reliable ground connection with the conductive shield of a fiber optic cable  40  without a significant disruption of the cable jacket  46 . 
     A preferred embodiment of the connector, illustrated by FIG. 1, includes two substantially similarly shaped clamp sections, designated  10 A and  10 B. Each section is preferably constructed from cold rolled steel or similar structurally rigid conductive material. Each section,  10 A,  10 B includes a central trough  22  defining a longitudinal channel with open semicircular ends. Linear flanges  14  transversely integrally extend from the longitudinal edges on each side of the central trough  22 . The linear flanges  14  include attachment points for fasteners which will attach the two sections into a rigid conductive assembly. Upper section  10 A has unthreaded holes  34  for receiving fasteners  16 . Lower section  10 B has corresponding threaded holes  18  to engage the fasteners  16  and facilitate assembly of the connector into a rigid clamp. 
     Referring now to FIGS. 2-4, a grounding screw  20  according to the present invention has a radially enlarged driving head  32 , a threaded shaft  28  integrally projecting from the head  32  and a sharpened cutting tip  26 , which surrounds a deep axial recess  30  in the shank  28 . In a preferred embodiment, the axial recess  30  passes entirely through the length of the shank  28  and head  32  of the screw  20 . The sharpened cutting tip  26  surrounds the axial recess  30  of the grounding screw  20 . In a preferred embodiment, the cutting tip  26  may be serrated to aid in penetrating the jacket  46  and removing any coating on the shield  44  which may interfere with electrical contact. 
     The trough of each clamp section has a longitudinal central axis A and defines a plurality of threaded openings  24 , which receive the threaded shanks  28  of the grounding screws  20 . In a preferred embodiment there are six openings  24  in the trough portion of each section. As best seen in FIG. 1, two of the openings  24  are placed in the arcuate middle of the central trough  22  so that the cutting tips  26  of grounding screws  20  received therein are aligned with and oriented toward the central axis A. Four openings  24  are placed in the arcuate walls of the central trough  22 , two on each side in a staggered angular relationship, so that the cutting tips  26  of grounding screws  20  received therein are oriented at corresponding angled relationships to the central axis A. The number and arrangement of grounding screws creates multiple opportunities to contact the cable shield from several angles on each side of the cable. 
     The length of each grounding screw  20  is selected so that the shank  28  of the grounding screw will penetrate the section  10 A,  10 B and protrude a pre-determined distance into the receiving cavity  12  defined by the assembled connector. The cutting tip  26  of the grounding screw  20  is prevented from penetrating further by the radially enlarged head  32  contacting the exterior surface  36  of the half shell  10 A,  10 B. 
     FIG. 5 illustrates the fiber optic connector  10  in an installed configuration surrounding a fiber optic cable  40  (partially illustrated) and provided with a ground lead  50  (partially illustrated). The fiber optic cable  40  has a conventional structure which includes fiber optic conductors  42 , a conductive shield  44 , linear strength members  48  and a protective jacket  46 . Lower section  10 B is illustrated in an installed position beneath the fiber optic cable  40  with the cable aligned with and partially received in the central trough  22 . Upper section  10 A is illustrated in an installed position over the fiber optic cable  40  with the cable aligned with the central trough  22 . The linear flanges  14  are mated with each other in a surface-to-surface relationship and held in place by fasteners  16 , thereby forming a rigid conductive assembly surrounding and clamped to the fiber optic cable  40 . 
     With reference to FIG. 5, the grounding screws  20  have been tightened so that the cutting tips  26  of the grounding screws  20  protrude into the receiving cavity  12  occupied by the fiber optic cable  40 . In doing so, the cutting edges  26  of the grounding screws  20  cut into the protective jacket  46  of the fiber optic cable  40 . As each grounding screw  20  penetrates the protective jacket  46 , a core of jacket material is formed within the longitudinal recess  30  of the shank  28  of the grounding screw  20 . The longitudinal recess  30  allows jacket material to migrate into the recess  30 , while the serrated, angled cutting tips  26  displace jacket material to the sides. The unique construction of the grounding screw  20 , with its longitudinal recess  30  and serrated angled cutting tip  26 , efficiently penetrates the thick tough jacket material to establish superior electrical contact with the cable shield  44 . 
     When fully tightened, the head  32  of each grounding screw contacts the outside surface  36  of the connector and the cutting edge  26  of the grounding screw  20  contacts the conductive shield  44  of the fiber optic cable  40  establishing a conductive path from the shield  44  to the connector clamp sections  10 A,  10 B. The grounding screws  20  cannot be overtightened because the head  32  bottoms out against the outside surface  36  of the connector sections  10 A,  10 B preventing further penetration. In a preferred embodiment the grounding screws  20  also secure and ground the linear strength members  48 . 
     Thus, a fiber optic shield connector according to the present invention can establish a reliable multi-point ground connection with the conductive shield of a fiber optic cable while leaving the cable jacket largely intact. No special tools or skills are required to affect a ground connection using the inventive fiber optic shield connector  10 . A ground lead  50  (partially illustrated) may be attached using the clamp fasteners  16 . The flexible conductor of the ground lead  50  may then be positioned and attached to a common ground point. The length of the lead  50  may be varied, allowing maximum flexibility in positioning the cable  40  within any enclosure (not illustrated). 
     A molded fiber optic shield connector enclosure according to one aspect of the present invention is illustrated in FIGS. 6-13. The enclosure includes a box-like nonconductive molded tub  80  and a mating box-like nonconductive molded cover  60 . The enclosure cover  60  includes a closed top  63  and opposed side walls  62  and end walls  64  which integrally project from the closed top. Inner end walls  66 , integrally project from the closed top  63  toward the open bottom of the cover. Each wall terminates in an edge which together define the open bottom of the cover  60 . The outer end walls terminate in outer end wall edges  68 ; inner end walls  66  terminate in inner end wall edges  70 ; and side walls  62  terminate in side wall edges  72 . The medial portions of the inner and outer end wall edges  68 ,  70  define identical rounded notches projecting toward the closed top  63  of the cover  60 . The notches  74  are bifurcated, having a first width at their respective edges  68 ,  70  and narrowing to a second width as the notch  74  approaches the closed top  63  of the cover  60 . The dual width of the rounded notches  74  allows the cable shield connector enclosure to effectively accommodate fiber optic cables of various diameters. 
     The side walls  62  of the enclosure cover  60  define outward facing rounded grooves  78  configured to mate with corresponding inward facing rounded protrusions  106  in the outer side walls  86  of the cable shield connector enclosure tub  80 . 
     The enclosure tub  80  is a rectangular molded unit having a closed bottom  82  and an open top. FIG. 7 illustrates the configuration of the outer side walls  86 , inner side walls  92 , outer end walls  88  and inner end walls  90  integrally projecting from the closed bottom  82 . Each wall terminates in an edge, which together define the open top of the tub. The outer side walls terminate in outer side wall edges  96 ; the inner side walls terminate in inner side wall edges  94 ; the outer end walls terminate in outer end wall edges  98 ; and the inner end walls terminate in inner end wall edges  100 . Inner side walls  92  and end walls  90  form a cradle and define a central space  104 . Identical rounded notches  84  are disposed in the inner end walls  90  and outer end walls  88 . The tub notches  84  are substantially identical in configuration to the cover notches  74  and are positioned in the tub end walls  88 ,  90  to align with the cover notches  74 , to form an unobstructed longitudinal opening  102  traversing completely through the assembled enclosure. 
     The enclosure tub  80  and cover  60  are configured so that cover outer side  62  and end  64  walls fit closely within tub outer side  86  and end  88  walls. Cover  60  side walls  62  fit between tub inner  92  and outer  86  side walls and cover inner end walls  66  fit closely outside tub inner end walls  90 . Cover  60  and tub  80  fit together in a press fit with cover  60  rounded grooves  78  aligned and mating with tub  80  rounded protrusions  106 . As the cover  60  is pushed within the tub  80  the tub rounded protrusions  106  engage transverse detents  79  provided in cover  60  rounded grooves  78 , thereby retaining the cover  60  in mated position with the tub  80 . The cover  60  and tub  80  are sufficiently flexible that the protrusions  106  displace from one detent  79  to another, snapping into place and holding the enclosure together. Several transverse detents  79  are provided to allow the cover  60  and tub  80  to be held in a range of stable mated positions. 
     FIGS. 8 and 9 show a top and bottom view, respectively, of an enclosure cover  60 . A rectangular central space  76  is defined by side wall edges  72  and inner end wall edges  70 . Aligned rounded notches  74  in the medial portions of the inner  70  and outer  68  end wall edges form an unobstructed path allowing the cable  40  to pass entirely through the assembled enclosure. The positioning and configuration of the rounded mating grooves  78  can be clearly seen in FIGS. 8 and 9. 
     FIG. 10 illustrates an end view of the enclosure cover. Rounded notches  74  in the inner  66  and outer  64  end walls are bifurcated, having a first width W 1  at their respective wall edge  68 ,  70  and tapering to a second width W 2  as the notch  74  approaches the closed top  63  of the cover  60 . 
     FIGS. 11 and 12 illustrate bottom and top views of the fiber optic shield connector enclosure tub  80 . Inner side  94  and end  100  walls form a cradle defining a rectangular central space  104  and are surrounded by opposed outer side  96  and end  98  walls in spaced relationship to form the double rectangular wall of the enclosure tub  80 . Side wall  86  rounded protrusions  106  are similar in shape to cover rounded grooves  78  and are positioned to engage the rounded grooves  78  when the tub  80  and cover  60  are in mating position (as illustrated in FIGS. 6,  7  and  14 ). 
     FIG. 13 illustrates an end view of the fiber optic shield connector enclosure tub  80 . Rounded notches  84  in the inner  90  and outer  88  end walls are substantially identical to cover notches  74 . Notches  84  have a first width W 1  at their respective wall edge  98 ,  100  and taper to a second width W 2  as the notch  84  approaches the closed bottom  82  of the tub  80 . Tub rounded notches  84  are aligned with cover rounded notches  74  so that when the enclosure is assembled, an opening  102  passes through the length of the enclosure. 
     FIG. 14 illustrates the fiber optic cable/shield connector/ground lead assembly of FIG. 5 functionally positioned for assembly within an enclosure formed from an enclosure tub  80  and cover  60 . Tub central space  104  is illustrated partially filled with water repellant gel  108 . In a preferred embodiment both the tub central space  104  and the cover central space  76  are partially filled with water repellant gel prior to assembly. The assembled fiber optic cable, shield connector and ground lead are positioned longitudinally in the cradle formed by tub inner side  92  and inner end  90  walls with the fiber optic cable  40  and ground lead  50  passing out of the enclosure through the rounded notches  84 . 
     The enclosure cover  60  is aligned with the enclosure tub  80  and pushed together by hand into mating position with the enclosure tub  80 . In a preferred embodiment, as the volume of the central spaces  76 ,  104  within the enclosure is reduced by manual pressure, excess gel is forced around the fiber optic cable  40  and ground lead  50  where they pass through the aligned notches  74 ,  84  to seal the interior space and form a water-tight, sealed enclosure surrounding the assembled fiber optic cable, shield connector and ground lead. In an assembled configuration the enclosure tub protrusions  106  snap into the transverse detents  79  in the cover rounded grooves  78  and retain the cover  60  in a compressed and mated position with the enclosure tub  80 . 
     The assembly including the fiber optic cable, shield connector, ground lead and enclosure according to the present invention forms a durable, highly weather resistant, reliable ground connection. The assembly is easily implemented by craft personnel with a minimum of training and requiring no special tools. Reliable, multi-point electrical contact with the fiber optic cable shield is created without a significant disruption of the cable jacket, thus minimizing risk of damage to fiber optic cable conductors or linear strength members. 
     While a preferred embodiment of the foregoing invention has been set forth for purposes of illustration, the foregoing description should not be deemed a limitation of the invention herein. Accordingly, various modifications, adaptations and alternatives may occur to one skilled in the art without departing from the spirit and the scope of the present invention.