Abstract:
Apparatus for providing strain relief of an optical ribbon cable caused by bending or other type of non-linear forces includes a base portion and a pivot portion both having a recess. The pivot portion is hingedly connected to the base portion and the recesses define a ribbon cable holding location. Compression members are provided in each of the recesses and define a gap therebetween for retaining optical fiber ribbon cables. The base portion and pivot portion are unitary and formed from a material which is non-opaque. An anchor portion is in contact with the base portion. The anchor portion has a tab member for indexing the apparatus with a support structure and a first latch member for securing the apparatus to a support structure. The hinge portion of the apparatus also has a second latch member for securing the hinge portion to the base portion.

Description:
FIELD OF INVENTION  
         [0001]    The present invention generally relates to optical fiber closures and, more particularly, to an optical fiber closure having improved optical fiber strain relief and fiber handling characteristics.  
         BACKGROUND OF INVENTION  
         [0002]    Optical communications refer to the medium and the technology associated with the transmission of information as light pulses. Many applications utilize an optical fiber network to establish optical communications between network locations. In order to enable optical communication and the flow of optical signals between network locations, various interconnections must be established between different optical fibers.  
           [0003]    As the different optical fibers approach an optical termination point, the density (number) of the fibers increases. Ribbon cables, an array of for example 12 or 24 individual fibers, are commonly used in such high density applications. Unfortunately, optical ribbon cables are commonly not covered or otherwise protected by a buffer tube. This condition makes the optical fibers susceptible to damage caused by bending strain. The bend radius R B  of the optical fibers is an important characteristic because it corresponds to the degree of “light leakage” in each of the individual fibers. That is, as light propagates through an individual fiber, a portion of the light will travel beyond the boundaries of the fiber if R B  is too small (corresponding to an angle of incidence of the light upon the fiber core that is greater than the critical angle for total internal reflection of the light).  
           [0004]    One solution to the routing and handling of ribbon cables is to use cable ties to bundle and secure a number of optical ribbon cables to one another. However, this solution does not allow for easy access to all of the ribbon cables should repair be necessary, or allow the ribbon cables to be easily secured into a predefined mounting position to ensure constant strain relief.  
         SUMMARY OF THE INVENTION  
         [0005]    These and other deficiencies of the prior art are addressed by the present invention of an apparatus for providing strain relief caused by bending or other types of non-linear forces. The apparatus includes a base portion having a recess and a pivot portion having a recess. The pivot portion is connected to the base portion and the base portion recess and the pivot portion recess define a ribbon cable holding location. The apparatus additionally has a first compression member provided in the base portion recess and a second compression member provided in the pivot portion recess. The compression members are selected from the group consisting of foam and rubber and define a gap therebetween for retaining a plurality of optical fiber ribbon cables.  
           [0006]    The apparatus is so configured that the base portion and pivot portion are unitary and molded from a material of which is non-opaque. In one embodiment, the clear material is selected from the group consisting of a polymer 12-based material.  
           [0007]    The apparatus also has an anchor portion in contact with the base portion. The anchor portion has a tab member for indexing the apparatus with a support structure and a first latch member for securing the apparatus to a support structure. The hinge portion of the apparatus also has a second latch member for securing the hinge portion to the base portion. In one embodiment of the invention, the anchor portion has a flat top surface. In a second embodiment of the invention, the anchor portion has a circular shaped top surface. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:  
         [0009]    [0009]FIG. 1 depicts a side view (with partial cross-sectional view) of the strain relief device of the subject invention;  
         [0010]    [0010]FIG. 2 depicts a top view of the strain relief device seen in FIG. 1;  
         [0011]    [0011]FIG. 3 depicts a side view of the strain relief device shown in FIG. 1 with a pivot portion in an open position;  
         [0012]    [0012]FIG. 4 depicts the strain relief device of FIG. 1 with the pivot portion in a closed position and securing a plurality of optical ribbon cables; and  
         [0013]    [0013]FIG. 5 depicts a side view of a second embodiment of the invention as seen along lines  5 - 5  of FIG. 2. 
     
    
       [0014]    To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0015]    [0015]FIG. 1 depicts a side view (with partial cross-sectional view) of a strain relief device  100  of the subject invention. FIG. 2 is a top view of the strain relief device  100  and the reader is invited to view both figures concurrently with this description. Specifically, the strain relief device  100  is shown arranged and secured to a frame member  90  (shown in a broken line format as it is not part of the specific invention) as one exemplary use of the subject invention. Those skilled in the art will realize that the strain relief device  100  can be configured in a variety of different ways so as to securely fit in any number of frames, shelves or the like used in organizing optical fibers ribbon cables in an optical communications network and/or any other system components that require neat, organized and secure arrangment. For the sake of clarity, the frame  90  is not shown in FIG. 2.  
         [0016]    The strain relief device  100  includes an anchor portion  102  upon which the rest of the device is built. The anchor portion  102  includes a rear tab  104  and a first latch (i.e., a front latch)  106 . The rear tab  104  allows for registration and positive positioning of the strain relief device  100  in an opening in the frame  90 . The front latch  106  allows for detachably securing the device  100  to the frame  90 . In other words, the front latch  106  can be operated any number of times to allow for the initial installation of the strain relief device  100  onto the frame  90  and subsequent detachments and reattachments of same for purposes of inspection, repair and the like of either the device or ribbon cables secured therein (discussed in detail below).  
         [0017]    Adjoining the anchor portion  102  is a base portion  110 . The base portion  110  includes a first flexible hinge  108  which transitions into the front latch  106  as it extends upwards towards the anchor portion  102 . The strain relief mechanism  100  also has a pivot portion  112  that is hingedly connected to the base portion  110  at second flexible hinge  114 . Pivot portion  112  also includes a second latch (i.e., a pivot portion latch)  116  that transitions from a third flexible hinge  128 . The second latch  116  is locked into place in an enclosure  118  in the base portion  110  especially designed and configured to receive the pivot portion latch  116 . One skilled in the art will realize that locking of the pivot portion to the base portion can also be easily attained by reversing the orientation of the second latch  116  and the enclosure  118 . That is, if the relevant portions of the strain relief device  100  were molded, or otherwise formed, “in reverse”, the enclosure  118  would be in the pivot portion  112  and the second latch would extend from the base portion  110  yet, the functionality would be identical.  
         [0018]    The various portions of the strain relief device  100  are fabricated from a polymer-12 based material. The material can be opaque or non-opaque. In one embodiment, the strain relief device  100  is fabricated from Grilamid, which is a clear plastic material manufactured and sold by K-Mac Plastics of Kentwood, Mich. One skilled in the art will realize that other types of materials are suitable for the application. Such materials are preferably non-opaque (so as to facilitate viewing of the fibers contained therein) and relatively durable (so as to withstand handling and installation into supporting frameworks and opening and closing of the device). A material such as Grilamid is known to also have desirable “living hinge” characteristics so as to provide the appropriate functionality to first hinge  108  and second hinge  114 . For example, hinges  108  and  114  and the portions on the device  100  to which they transition are all formed as a single, unitary piece so as to reduce the number of components of the subject device  100 . For example, first hinge  108  and second hinge  114  are relatively thin areas of material of which the strain relief device  100  is constructed.  
         [0019]    One skilled in the art will understand that the terminology “living hinge” means making second hinge  114  substantially thin enough (and in one embodiment approximately 10 mil) so as to provide hinged motion between the base portion  110  and the pivot portion  112  yet remain durable enough to maintain structural integrity of the overall device. An appropriate thickness of first hinge  108  will allow it to operate repeatedly in the desired manner. It will also be understood to one skilled in the art that a thin layer material version of the strain relief device  100  is not the only way hinged attachment of these components can be made and that other suitable materials or methods of attachment are possible. Such suitable alternate materials can be selected from the group consisting of nylon and polypropylene as these materials have suitable living hinge characteristics. Additionally, the hinge design can also be a standard detachable hinge arrangement.  
         [0020]    Base portion  110  is further provided with a base portion recess  120 . Similarly, pivot portion  112  is provided with a pivot portion recess  124 . Both the base portion recess  120  and the pivot portion recess  124  contain a compression member therein. Specifically, a first compression member  122  is sized to fit in base portion recess  120  and second compression member  126  is sized to fit in pivot portion recess  124 . Each of the compression members  122  and  126  are fabricated from a highly elastic and high friction type material so as to allow the necessary amount of compression to hold ribbon cables therebetween while remaining sufficiently durable so as to not lose their strength or compressive abilities over time. In one embodiment of the invention, the compression members  122  and  126  are fabricated from materials selected from the group consisting of rubber and foam. In one particular embodiment of the subject invention, the compression members  122  and  126  are selected from the group consisting of neoprene foam and rubber foam.  
         [0021]    [0021]FIG. 3 depicts the strain relief device  100  of the subject invention wherein the hinge portion  112  is delatched and swung away from the base portion  110 . In this manner, one or more ribbon cables can be arranged in an opening  300  provided between the stationary base portion  110  and the hinge portion  112 . Specifically, in FIG. 3 a plurality of ribbon cables  302  (viewed cross-sectionally to see respective pluralities of individual optical fibers contained therein) are positioned into opening  300 , yet not completely secured to the strain relief device  100 .  
         [0022]    [0022]FIG. 4 depicts the strain relief device  100  of FIG. 1 with the pivot section  112  in a closed position and securing the plurality of optical ribbon cables  302 . Specifically, once the hinge portion  112  of the strain relief device  100  is latched into place, the opening  300  which receives the plurality of ribbon cables  302  is narrowed into a gap  400  between first and second compression members  122  and  126 , respectively. Accordingly, the plurality of ribbon cables  302  are secured into position by virtue of the compressive forces of the first and second compression members  122  and  126 , respectively, and/or neighboring ribbon cables  302 . It should be noted that the ribbon cables  302  do not need to be arranged in any specific order or arrangement. That is, the compressive forces generated by the strain relief device  100  do not damage the ribbon cables  302  and tend to substantially immobilize the ribbon cables  302  from directional movements that may cause the damaging bends and/or strain.  
         [0023]    [0023]FIG. 5 depicts a side elevation view of a second embodiment of the strain relief apparatus  100  as viewed along lines  5 - 5  of FIG. 2. Specifically, FIGS. 1-4 depict the first embodiment of the apparatus  100  as having a flat topped anchor portion  102 . FIG. 5 depicts the apparatus  100  as having a domed anchor portion  102 . In detail, strain relief apparatus  100  is shown with the base portion  110  and pivot portion  112  clamping a plurality of ribbon cables  302  in place. The anchor portion  102  includes a circular or domed shaped surface  502  which further increases strain relief of the ribbon cables  302 . As the ribbon cables  302  exit the strain relief apparatus  100 , the ribbon cables  302  are wrapped around the domed top surface  502  which provides an sufficiently large bend radius R B  to further prevent damage or excessive signal degradation.  
         [0024]    For sake of clarity on the use and operation of the “living hinges,” the operation of first latch  106  is depicted. Specifically, first hinge  108 , being a “living hinge” type arrangement, allows flexibility of the latch  106  about the hinge  108 . Specifically, first latch  106  is shown in a locked first position ( 106 A) and by virtue of the flexibility of first hinge  108 , it is possible to move first latch  106  into an unlocked position ( 106 B). This unlocked position  106 B allows the strain relief device  100  to be detached from the frame or shelf  90  so that it can be inspected and/or replaced as necessary. It will be noted that second latch  116  operates in substantially the same manner as first latch  108  by virtue of the “living hinge” capabilities of third hinge  128  as well.  
         [0025]    The advantages of the subject invention are readily realized. Specifically, the unitary construction of the strain relief device  100  facilitates handling (i.e., opening and closing) of the strain relief device  100  without the problem of misalignment of the base portion  110  and the hinge portion  112 . The total number of molds to create the device (and parts resulting therefrom) is reduced from at least two to one. The strain relief device  100  of the subject invention also has a low profile which allows for mounting numerous ribbon cables  302  simultaneously. The invention is sized so as to fit and be installed into existing optical communication network components (i.e., high identity applications including Lambda routers, high density optical closures, fiber cross connect shelves such as LGX shelves, LIUs and the like). Additionally, the device requires no additional fasteners for installing or subsequent removal and reinstallation. If the preferred clear material is used for to fabricate the device, visual inspection is facilitated without having to handle the device of the fibers contained therein. Lastly, the design of the device allows for strain relieving both 12 fiber or 24 fiber optical ribbon cables. Accordingly, this technology is adaptable to older optical communication systems as well as state-of-the-art equipment.  
         [0026]    Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings.