Abstract:
An optical fiber cable management panel includes drawer assemblies, each including a drawer slidable within a chassis. The chassis incorporates a grounding point, and the drawer assemblies are electrically connected to the grounding point by a grounding strap. The grounding strap flexes to allow the slidable movement of the drawer relative to the chassis. The strap may be folded one or more times. The strap may be bolted, welded, or otherwise conductively and non-rotatably affixed at each end to the drawer and the chassis so as to maintain a constant position within the assembly and a constant electrical connection between the drawer and the grounding point.

Description:
TECHNICAL FIELD 
       [0001]    This disclosure concerns management of optical fiber cables. In particular, this disclosure relates to grounding of optical fiber cable storage devices in the telecommunications industry. 
       BACKGROUND 
       [0002]    Cable termination, splice, and storage devices are known including, for example, devices shown in U.S. Pat. Nos. 6,438,310 and 6,504,988, both assigned to ADC Telecommunications, Inc. Both of these patents concern devices with slidable drawers for storage and management of the optical fiber cables. The slidable drawers are connected to a grounded chassis via a pair of ball bearing slides. These ball bearings provide insufficient and unreliable grounding for active fiber and electronics stored in the drawers. The slidable drawers may also be connected to the chassis via a non-conductive slide mechanism, or may be connected to a non-conductive portion of the chassis. So, reliance on the slide mechanism for grounding may not be effective. 
         [0003]    The slidable drawers contain the trays that hold many strands of optical fiber. There is a growing need for added active electronic or electro-optical devices, such as LED driver and display combinations, optical amplifiers, or lasers to be included in the drawers. As more active and passive electronic and electro-optical equipment is added to the drawers, a reliable grounding mechanism is needed. 
         [0004]    Therefore, improvements are desirable. 
       SUMMARY 
       [0005]    In one aspect, the present invention concerns an optical fiber cable management system. The management system includes a chassis incorporating a grounding point and a drawer assembly slidably mounted within the chassis on a drawer slide. A flat grounding strap is attached to the grounding point and the sliding drawer. The strap flexes to accommodate the movement of the drawer along the drawer slide. 
         [0006]    A method of grounding an optical fiber cable management panel is also provided. This method includes providing a chassis incorporating a grounding point and a drawer slidably mounted within the chassis. The method also includes electrically connecting the grounding point to the slidable drawer with a grounding strap. Opposing ends of the grounding strap are attached to the drawer and grounding point respectively so as allow the strap to flex. The strap flexion accommodates the movement of the drawer relative to the chassis. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a perspective view of a cable management panel, depicting two closed drawers; 
           [0008]      FIG. 2  is a top view of the panel of  FIG. 1 ; 
           [0009]      FIG. 3  is a top view of the panel of  FIG. 2  with one drawer in the open position; 
           [0010]      FIG. 4  is a top view of another possible embodiment of the cable management panel with one of the drawers in the open position; 
           [0011]      FIG. 5  is a side view of the area of the panel of  FIG. 3  between the drawer and chassis; 
           [0012]      FIG. 6  is a side view of the area of the panel in  FIG. 3  inside the drawer and between the drawer and chassis. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    A cable management panel or module is depicted in  FIG. 1  generally at  30 . The panel  30  includes one or a plurality of drawer assemblies  32 . In the one shown in  FIG. 1 , the panel  30  includes two drawer assemblies  32 . Each of the drawer assemblies  32  includes a chassis  34  and a drawer  36  slidably mounted within the chassis  34 . 
         [0014]    Each drawer  36  may include cable management structure, for example, devices for storing the cables or connecting the cables to other cables or fiber optic devices, such as attenuators, couplers, switches, wave division multiplexers, splitters or splices. Each drawer  36  may also include active electronic or electro-optical devices, such as LED driver and display combinations, optical amplifiers, or lasers. Each drawer  36  includes two latches  40  to secure the drawer  36  in a closed position (the position shown in  FIG. 1 ). 
         [0015]    Each drawer  36  includes a base  42 , a front wall  44  and a rear wall  46 . Note that the drawer  36  is absent of side walls, or is “side wall-free.” This structure allows for cable entry and exit and prevents cable damage during sliding movement of the drawers  36  when accessing the cables and connectors or other devices in the drawer  36 . The base  42 , front wall  44  and rear wall  46  together define a storage interior  48  for holding and storing the cables. 
         [0016]    The chassis  34  incorporates a grounding point for electrical connection to a facility ground, such as a bolt  54 . To ground the drawer  36 , the rear wall  46  is electrically connected to the bolt  54  through a grounding strap  50 . The grounding strap  50  is flexible and is made of stainless steel, nickel silver, or some similar conductive flexible material. 
         [0017]    Each storage interior  48  is sized for receiving cable management and/or distribution structures. When the drawer  36  is in the closed position, the cables and management or distribution structures in the storage interior  48  are protected. In preferred embodiments, the distribution structures can be conveniently mounted on a tray insert (not shown) that drops into the storage interior  48 . Example tray inserts are shown and described in U.S. Pat. Nos. 6,438,310 and 6,504,988, the disclosures of which are hereby incorporated by reference. This allows for convenient structuring of the drawer  36  to serve one or more desired functions in the panel  30 . In the embodiment illustrated, each of the drawers  36  is constructed to be stackable and linkable to form sub-cable management panels  31 . Such modularity also allows for ease of use for a variety of different needs for the cable management system. 
         [0018]    Referring to  FIG. 2 , a top view of the cable management panel with the drawer  36  in a closed position is shown. The grounding strap  50  is attached at each end to chassis  34  and rear wall  46  of drawer  36 , respectively. This conductive attachment may be accomplished with bolts  52  and  54 . When the drawer  36  is in the closed position, the strap  50  is compressed into a folded position where ends of the strap  50  approach each other. The bolt  54  attached to the chassis  34  provides a grounding point for the cable management panel. Grounding may be accomplished by electrically connecting the bolt  54  to a facility electrical ground  55 . 
         [0019]    The drawer  36  has conductive properties, and includes rear wall  46  that in the preferred embodiment is comprised of conductive material such as metal. The rear wall  46  is electrically connected to any electrical equipment contained within drawer  36 , possibly through attachment to a metallic base of the drawer  36 . One of skill in the art will recognize that rear wall  46  need not be conductive. In this case, the metallic base of drawer  36  or other elements requiring a ground connection may be electrically connected to bolt  52  by a conductive wire (see, for example,  FIG. 6 ). 
         [0020]    The grounding strap  50  electrically connects the drawer  36  to the chassis  34 . The grounding strap  50  is attached at each end to chassis  34  and rear wall  46  of the drawer  36 , respectively. In the preferred embodiment, the grounding strap  50  has two legs  51   a  and  51   b . The legs  51   a  and  51   b  are separated by a bend  51   c . The legs  51   a  and  51   b  have end regions  51   d  and  51   e , respectively. End region  51   e  is attached to the rear wall  46  by a bolt  52 . Likewise, end region  51   d  is attached to the chassis  34  by a bolt  54 . The end regions  51   d  and  51   e  may be attached in one or more places or may be otherwise supported so that gravity or other forces do not cause it to rotate out of a preferred position, as shown (see also  FIG. 5 ). Bolts  52  and  54  may be offset with respect to each other so as to minimize the distance between rear wall  46  and chassis  34  when drawer  36  is in a closed position. 
         [0021]    Various structures or combinations of structures may be used for affixing the strap  50  to the chassis  34  and rear wall  46  of the drawer  36  in such a manner that the affixing structure maintains continuous electrical contact and a grounding point while preventing rotation of the strap  50 . In a preferred embodiment, bolts  52  and  54  affix the strap  50  to the chassis  34  and the rear wall  46 , while flanges on the rear wall  46  and chassis  34  prevent rotation out of a preferred position (as shown and discussed in  FIGS. 5 and 6 , below). In an alternate embodiment, a second affixing structure such as a rivet, weld, or other mechanical attachment configuration such as a lance may be used in combination with bolt  52  and/or  54  to prevent rotation of the strap  50  out of a preferred position. In such an embodiment, the flanges shown and described in  FIGS. 5 and 6  are optional. 
         [0022]    In another embodiment of the present disclosure, an alternative affixing structure may be substituted for bolt  52 . For example, a rivet, weld, or other mechanical attachment configuration such as a lance may be used to attach the grounding strap  50  to the rear wall  46  of drawer  36  instead of bolt  52 . The bolt  54  is a preferred structure for attaching a discreet grounding conductor to the facility electrical ground  55 ; however, alternate conductive attachment mechanisms providing a grounding point may similarly be implemented. These alternative affixing structures may be used in combination with the flanges shown and described in  FIGS. 5 and 6 , or any of the other structures mentioned herein for maintaining the grounding strap in a preferred position. 
         [0023]    Referring to  FIG. 3 , a top view of the cable management panel with the drawer  36  in an open position is shown. Each drawer  36  is slidable relative to chassis  34  by way of two drawer slides  38  on opposite sides of the chassis  34 . The grounding strap  50  is flexible, and flexes into a “wishbone” shape when the drawer  36  is in an open position. The grounding strap  50  defines a conductive path from the drawer  36  to the grounding point  55  when the drawer  36  is in either an open or a closed position. 
         [0024]    Referring to  FIG. 4 , a further embodiment of the present disclosure is shown, with the drawer  36  in an open position. A grounding strap  150  attaches to the chassis  34  and the rear wall  46  of drawer  36 . The grounding strap is separated into three legs  151   a ,  151   b , and  151   c , respectively. The three legs  151   a ,  151   b , and  151   c  are separated by two folds  151   d  and  151   e . Two regions of the grounding strap  151   a  and  151   c  have end regions  151   f  and  151   g . End region  151   f  attaches to the chassis  34  with a fastener such as a bolt  54 . End region  151   g  attaches to the rear wall  46  with a fastener such as a bolt  52 . The drawer  36  is slidable relative to the chassis  34  by way of two drawer slides  38  on opposite sides of the chassis  34 . In this embodiment, the grounding strap  150  flexes into a “z” or “double-wishbone” shape to accommodate the drawer  36  as it slides on the drawer slides  38  into open or closed positions. 
         [0025]    Referring to  FIG. 5 , a side view of the area between the chassis  34  and the rear wall  46  of the drawer  36  is shown for the open drawer configuration (see, for example,  FIG. 3 ) in a possible embodiment of the present disclosure. The drawer  36  has rear wall  46  that could be conductive, and may be made from metal. The chassis has a top flange  56   a  and a bottom flange  56   b . The drawer  36  has a top flange  56   c  and a bottom flange  56   d  adjacent to the rear wall. The vertical distance between the top flanges  56   a  and  56   c  and the bottom flanges  56   b  and  56   d  is the same, and allows a grounding strap  50  to fit between the flanges. The grounding strap  50  has two legs  51   a  and  51   b . The legs are separated by a fold  51   c . The legs  51   a  and  51   b  have end regions  51   d  and  51   e , respectively. The end region  51   e  is attached to the drawer  36  by a fastener  52 . The end region  51   d  is attached to the chassis  34  by a fastener such as a bolt  54 . The end regions  51   d  and  51   e  have a width that corresponds to the distance between the top and bottom flanges of the chassis  34  and drawer  36 , respectively. This prevents the grounding strap  50  from pivoting about an axis defined by bolts  52  and  54 , yet allows only two bolts to be used. 
         [0026]    Referring to  FIG. 6 , a side view of the area inside the drawer  36  and between the chassis  34  and the rear wall  46  of the drawer  36  is shown for the open drawer configuration (see, for example,  FIG. 3 ) in a possible embodiment of the present disclosure. The drawer  36  has rear wall  46  that need not be conductive, and chassis  34  may also no longer be conductive. A grounding strap  50  is attached to the drawer  36  and chassis  34  by fasteners, such as bolts  52  and  54 , respectively. An active device  58  requiring grounding, such as LED driver and display combinations, optical amplifiers, or lasers, may be located within the drawer  36 . The active device  58  is attached to a wire  60  that provides an electrical connection between the device  58  and bolt  52 . Bolts  52  and  54  are conductive, and along with grounding strap  50  and wire  60  define a conductive path from the device  58  in the interior of drawer  36  to the exterior of the chassis  34 , allowing for electrical connection to the facility electrical ground  55 . One of skill in the art will recognize that additional wires may be connected from one or more components or conductive planes (such as the metallic base described above) in the drawer  36  to bolt  52  to provide multiple grounding paths. 
         [0027]    When grounding straps  50 ,  150  are used, grounding of the drawers  36  is through straps  50 ,  150  and bolts  52  and  54 . Drawer slides  38  no longer need to define an electrically conductive path. Drawer slides  38  can be made from non-electrically-conductive materials if desired. 
         [0028]    The above specification, examples and data provide a description of the manufacture and use of the composition of the disclosure. Since many embodiments of the disclosure can be made without departing from its spirit and scope, the invention resides in the claims hereinafter appended.