Abstract:
A bend radius guide provides effective cable management and bend radius control to prevent microbending of fiber optic cables entering and exiting cable distribution enclosures. Using arcuate surfaces, the guide provides bend radius control to prevent against microbending at distribution enclosure openings in directions horizontal or vertical to the enclosure depending upon the placement of the guide. When used in conjunction, bend radius guides prevent microbending in both horizontal and vertical directions concurrently. Bend radius guides used in conjunction can manage a number of fiber cables while still allowing access to individual cables through an angled slot formed by the joining of two guides.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to fiber optic cable distribution enclosures and, in particular, a device providing bend radius control of fiber optic cable entering and exiting said enclosures. 
     Fiber optical cable allows for high data transmission rates over long distances but its usage is limited by a minimum bend radius. It is desirable to control the radius of the fiber optic cable to prevent the fiber from being bent beyond the minimum bend radius. In addition, it is desirable to eliminate microbending, which occurs, for example, when a fiber optical cable is pulled over a sharp corner. Microbending results in unacceptable high attenuation of the optical signal and degrade or interrupt signal transmission. 
     Fiber optic cable that is brought into a building for use in transmitting coded or modulated signals, such as telephone (voice), cable (video), or computers (data) signals, must be distributed throughout the building to each location that requires access to the information being transmitted. To facilitate that distribution, an enclosure is typically utilized to house and manage the dispersal of the fiber. FIG. 1 shows an example of such a distribution enclosure  10 , which is described fully in U.S. Pat. No. 5,945,633, and is incorporated herein by reference. Distribution enclosure  10  allows cables to enter and exit the enclosure at openings  12 . In many cases, as many as 72 fibers are distributed within a single enclosure and several of these enclosures are attached to a rack. In larger systems, a room full of these racks serves as a central hub from which thousands of fibers are distributed. 
     The multitude of fibers entering and exiting distribution enclosures and the proximity of hardware equipment in a fiber optic cable distribution system, such as described above, result in a high incidence of microbending. Any fiber entering or exiting an enclosure can be subject to microbending by being pulled tight across a sharp edge or pinched between two pieces of hard plastic or sheet metal. The improper functioning caused by the microbending of fibers entering or exiting a distribution enclosure degrades the operability of the entire distribution system. 
     Prior art devices have been used to protect fiber optic cable from sharp surfaces. A rotatable grommet, shown generally at  20  in FIG.  2  and described fully in U.S. Pat. No. 5,806,140, incorporated herein by reference, is designed for opening or closing access to a distribution panel opening  12  through which fiber optic cable travels. The rotatable grommet  20  protects the fiber optic cable from a sharp edge of the enclosure  10  but does not substantially control the bend radius of the fiber optic cable. Although the device of FIG. 2 is well suited for its intended purpose, it is understood that improvements in the control of fiber optic cable bend radius is needed. 
     SUMMARY OF THE INVENTION 
     The above-discussed and other drawbacks and deficiencies of prior art are overcome or alleviated by the bend radius guide of the present invention. The bend radius guide provides effective cable management and bend radius control to prevent microbending of fiber optic cables entering and exiting cable distribution enclosures. Using arcuate surfaces, the guide protects fiber optic cable against microbending at distribution enclosure openings in directions horizontal or vertical to the enclosure depending upon the placement of the guide. When used in conjunction, bend radius guides prevent microbending in both horizontal and vertical directions concurrently. Bend radius guides used in conjunction can protect numerous fiber optic cables while still allowing access to individual cables through an angled slot formed by the joining of two guides. 
     The bend radius guide requires no tools or fasteners for installation. The secure installation of this device is achieved through a snap on fit between an undercut in the device and raised dimples on the enclosure walls. The bend radius guide has a universal design, allowing installation in any cutout (front or back, left or right, top or bottom) on a variety of cable distribution enclosures. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several FIGURES: 
     FIG. 1 is a perspective view of a conventional cable distribution enclosure; 
     FIG. 2 is a perspective view of a conventional rotatable grommet for opening and closing access to the cable entrance or exit of a cable distribution enclosure; 
     FIG. 3 is a side plan view of a bend radius guide in an exemplary embodiment of the invention; 
     FIG. 4 is a perspective view of the bend radius guide of FIG. 3; 
     FIG. 5 is a side plan view of the bend radius guide of FIG. 3; 
     FIG. 6 is a front plan view of bend radius guide; 
     FIG. 7 is a perspective view of a bend radius guide installed on an exemplary cable distribution enclosure; and 
     FIG. 8 is a perspective view of two bend radius guides installed concurrently on an exemplary cable distribution enclosure. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3 is a side plan view of a bend radius guide, shown generally at  100 , as an exemplary embodiment of the present invention. Bend radius guide  100  includes a first member  102 , a second member  104 , and a third member  106 . First member  102  and third member  106  are arranged substantially parallel to each other and are rigidly joined substantially perpendicular to second member  104  such that an approximate U-shape is formed. First member  102  is a thin trapezoidal solid with inner surface  103  and outer surface  105 . First member  102  has fixed end  107  and beveled end  109 . Fixed end  107  is joined substantially perpendicular to second member  104 . Beveled end  109  is free-standing and at an angle with respect to fixed end  107  (see FIG.  6 ). Second member  104  is an arcuate shape having a radius to prevent signal degradation in fiber optic cable passing over the second member  104 . In an exemplary embodiment, the radius of second member  104  is greater than the minimum bend radius of the cable to be used with the bend radius guide  100 . Second member  104  includes convex inner surface  108  and concave outer surface  110 . Third member  106  is an arcuate shape having a radius to prevent signal degradation in fiber optic cable passing over the second member  104 . In an exemplary embodiment, the radius of third member  106  is greater than the minimum bend radius of the cable to be used with the bend radius guide  100 . Third member  106  includes convex inner surface  112  and concave outer surface  114 . Third member  106  extends further from second member  104  than does first member  102 . Second member  104  contains contoured surfaces  116  and  117  that abut first member  102  and third member  106 , respectfully, to maintain an arcuate shape at the joints of said members. 
     FIG. 4 is a perspective view of the bend radius guide  100  of FIG. 3. A first flange  118  and a second flange  120  are mounted continuously to outer surface  114 , contoured surface  117 , and outer surface  110 . First flange  118  and second flange  120  are positioned parallel to each other. First flange  118  has interior and exterior surfaces  118 A and  118 B, respectfully. Interior surface  118 A has a semi-cylindrical cut-out  119  (see FIG.  5 ). Second flange  120  has interior and exterior surfaces  120 A and  120 B, respectfully. Interior surface  120 A has a semi-cylindrical cut-out  121 . Channel  122  is formed by the interfacing of semi-cylindrical cut-outs  119  and  121 . Groove  123  is formed by the interfacing of the remaining portions of interior surfaces  118 A and  120 A. First and second flanges  118  and  120  have cut-out areas  126  and tapered sections  128  at contoured surface  117  to aid in installing bend radius guide  100  on a distribution enclosure as discussed in more detail herein. First and second flanges  118  and  120  terminate at inner surface  103  of first member  102 . First and second flanges  118  and  120  also terminate at and bore through top surface  130  of member  106 . Support members  124  are mounted on outer surface  110  perpendicular and adjoined to first and second flanges  118  and  120  to give support to said flanges and to second member  104 . 
     FIG. 5 is a top plan view of bend radius guide  100  depicting the convex inner surface  108  of second member  104  and top surfaces,  128  and  130 , of first member  102  and third member  106 , respectfully. Top surface  128  is substantially rectangular in shape. Top surface  130  is substantially semi-cylindrical in shape. Channel  122  and groove  123  bore through top surface  130  to create notch  132 . Notch  132 , channel  122 , and groove  123  combine to facilitate in the installation of bend radius guide  100  onto cable distribution enclosures as discussed in further detail below. Groove  123  is substantially rectangular in shape and runs with cylindrical channel  122  traversing outer surface  114 , contoured surface  117 , and outer surface  110  and then terminates at inner surface  103  of first member  102 . 
     FIG. 6 is a side plan view of bend radius guide  100  showing outer surface  105  of first member  102  and inner surface  112  of third member  106 . First member  102  is shorter in length than third member  106  and the distal end of first member  102  that is not joined to second member  104  is beveled to facilitate the concurrently use of two bend radius guides, as is discussed further below. 
     The use of bend radius guide  100  is now discussed. FIG. 7 shows bend radius guide  100  installed on a cable distribution enclosure  240 . Cable distribution enclosure  240  has cable openings  242  through which cable enters and/or exits said enclosure. Cable openings  242  are substantially rectangular in shape and have a first edge  244 , a second edge  246 , a third edge  248 . Edges  244 ,  246 , and  248  are comprised of the casing  252  of cable distribution enclosure  240 . Casing  252  has a plurality of protuberances  254  which are adjacent to and parallel to edges  244 ,  246 , and  248 . 
     An exemplary installation of bend radius guide  100  to cable distribution enclosure  240  begins by aligning bend radius guide  100  such that second member  104  abuts either edge  244  or  248 , depending on desired placement, at interior surfaces  118 A and  120 A of first flange  118  and second flange  120 , respectfully. Bend radius guide  100  is further positioned such that third member  106  abuts edge  246  at interior surfaces  118 A and  120 A of first flange  118  and second flange  120 , respectfully. 
     Next, a force is applied perpendicular to inner surface  108  of second member  104  causing edge  244  or  248 , depending upon placement of guide  100 , to enter channel  122 . Additional force is placed in the same direction causing edge  244  or  248 , depending upon placement of guide  100 , to enter groove  123 , simultaneously causing protuberances  254  to enter channel  122  snapping second member  104  onto cable distribution enclosure  240 . Then, a force is applied perpendicular to inner surface  112  of third member  106  causing edge  246  to enter channel  122 . Additional force is applied in the same direction causing edge  246  to enter groove  123  simultaneously causing protuberances  254  to enter channel  122  snapping third member  106  onto cable distribution enclosure  240 . Bend radius guide  100  is now installed and may be used to accommodate cables entering or exiting cable distribution enclosure  240 . In the position shown in FIG. 7, the bend radius guide  100  is primarily used for guiding cables entering or existing enclosure  240  below the enclosure as shown by arrow A. Of course, the bend radius guide  100  may be mounted such that second member  104  is placed against edge  244  for guiding cables entering or exiting enclosure  240  from above the enclosure. 
     Bend radius guide  100  installed on cable distribution enclosure  240 , as described, provides multi-directional control of bend radius thus preventing the deleterious effects of microbending as discussed above. The directions of bend radius control provided by the installation of guide  100  correspond to the inner surfaces of said guide. The convex inner surface  108  of second member  104  protects cables entering or exiting cable distribution enclosure  240  against microbending in a direction substantially perpendicular to either edge  248  or  244 , depending on the chosen installation arrangement. Convex inner surface  112  of third member  106  provides bend radius control for cables entering or exiting enclosure  240  in a direction substantially perpendicular to edge  246 . Contoured surface  117  provides bend radius control for those cables entering or exiting enclosure  240  in a direction substantially bisecting the angle formed by the intersection of second member  104  and third member  106 . Contoured surface  116  provides bend radius control for those cables entering or exiting enclosure  240  in a direction substantially bisecting the angle formed by first member  102  and second member  104 . First member  102  acts as a collar preventing cables entering or exiting cable distribution enclosure  240  from slipping outside of bend radius guide  100 . 
     Additional directions of bend radius control are provided when two bend radius guides  100  are installed concurrently in opening  242  of cable distribution enclosure  240  as is depicted in FIG.  8 . An exemplary method of installation is provided as follows. A first bend radius guide  100  is positioned such that second member  104  abuts edge  248  and third member  106  abuts edge  246  at interior surfaces  118 A and  120 A of first and second flanges  118  and  120 , respectfully. Force is applied substantially perpendicular to second member  104  causing edge  248  to enter channel  122  and then subsequently enter groove  123 , simultaneously causing protuberances  254  to enter channel  122  snapping second member  104  onto cable distribution enclosure  240 . Next, a force is applied substantially perpendicular to third member  106  causing edge  246  to enter channel  122  and then subsequently enter groove  123 , simultaneously causing protuberances  254  to enter channel  122  snapping third member  106  onto cable distribution enclosure  240 . First bend radius guide  100  is now properly installed on cable distribution enclosure  240 . 
     Referring to FIG. 8, a second bend radius guide  100  is positioned such that second member  104  abuts edge  244  and third member  106  abuts edge  246  at interior surfaces  118 A and  120 A of first and second flanges  118  and  120 , respectfully. Force is applied substantially perpendicular to second member  104  causing edge  244  to enter channel  122  and then subsequently enter groove  123 , simultaneously causing protuberances  254  to enter channel  122  snapping second member  104  onto cable distribution enclosure  240 . Next, a force is applied substantially perpendicular to third member  106  causing edge  246  to enter channel  122  and then subsequently enter groove  123 , simultaneously causing protuberances  254  to enter channel  122  snapping third member  106  onto cable distribution enclosure  240 . Second bend radius guide  100  is installed on cable distribution enclosure  240  on edges  246  and  244  adjacent to the first bend radius guide  100  so that the ends of third members  106  abut against each other as shown in FIG.  8 . 
     Bend radius guides, concurrently installed, can retain and provide bend radius control for a plurality of fiber cables. Concurrent installation provides multi-directional bend radius control beyond that offered by installation of a single bend radius guide. The directions of bend radius control provided by concurrent installation corresponds to the inner surfaces of the concurrently installed bend radius guides. Inner surfaces  108  of concurrently installed bend radius guides  100  provide bend radius control in directions parallel to edge  246  of said enclosure. Inner surfaces  112  of concurrently installed bend radius guides  100  provide bend radius control in directions substantially perpendicular to edge  246  of said enclosure. Contoured surfaces  117  of concurrently installed bend radius guides  100  provide bend radius control in a direction substantially bisecting the angle created by the intersection of second member  104  and third member  106 . Contoured surfaces  116  of bend radius guides  100  in FIG. 8 provide bend radius control in a direction substantially bisecting the angle created by the intersection of first member  102  and second member  104 . 
     First members  102  of concurrently installed bend radius guides  100  properly retain and allow access to cables entering or exiting a cable distribution enclosure  240 . First members  102  act as a collar that prevents cables entering or exiting cable distribution enclosure  240  from slipping outside of bend radius guides  100 . Beveled ends  109  of first members  102  are juxtaposed and do not meet when two bend radius guides  100  are installed as described above with reference to FIG.  8 . The resulting slot  256  is angled relative to fixed ends  107  of first members  102 . Slot  256  allows access to individual cables without requiring removal of either concurrently installed bend radius guide  100 . Slot  256  is angled to prevent unintended cable withdrawal. A plurality of cables retained by a concurrently installed bend radius guide may be accessed by removing one bend radius guide. Bend radius guide  100  is removed simply by applying a force by hand on outer surfaces  110  and  114 , opposite that used in the installation process, until bend radius guide  100  snaps free.