# Patent

## Title
System and method of grounding fiber storage trays

## 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.

## Background
This application is a continuation of application Ser. No. 11/071,374, filed Mar. 2, 2005, now U.S. Pat. No. 7,362,942 which application is incorporated herein by reference in its entirety.


TECHNICAL FIELD
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
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.
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.
Therefore, improvements are desirable.
SUMMARY
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.
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
FIG. 1 is a perspective view of a cable management panel, depicting two closed drawers;
FIG. 2 is a top view of the panel of FIG. 1;
FIG. 3 is a top view of the panel of FIG. 2 with one drawer in the open position;
FIG. 4 is a top view of another possible embodiment of the cable management panel with one of the drawers in the open position;
FIG. 5 is a side view of the area of the panel of FIG. 3 between the drawer and chassis;
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
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.
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).
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.
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.
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.
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.
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).
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 51a and 51b. The legs 51a and 51b are separated by a bend 51c. The legs 51a and 51b have end regions 51d and 51e, respectively. End region 51e is attached to the rear wall 46 by a bolt 52. Likewise, end region 51d is attached to the chassis 34 by a bolt 54. The end regions 51d and 51e 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.
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.
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.
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.
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 151a, 151b, and 151c, respectively. The three legs 151a, 151b, and 151c are separated by two folds 151d and 151e. Two regions of the grounding strap 151a and 151c have end regions 151f and 151g. End region 151f attaches to the chassis 34 with a fastener such as a bolt 54. End region 151g 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.
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 56a and a bottom flange 56b. The drawer 36 has a top flange 56c and a bottom flange 56d adjacent to the rear wall. The vertical distance between the top flanges 56a and 56c and the bottom flanges 56b and 56d is the same, and allows a grounding strap 50 to fit between the flanges. The grounding strap 50 has two legs 51a and 51b. The legs are separated by a fold 51c. The legs 51a and 51b have end regions 51d and 51e, respectively. The end region 51e is attached to the drawer 36 by a fastener 52. The end region 51d is attached to the chassis 34 by a fastener such as a bolt 54. The end regions 51d and 51e 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.
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.
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.
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.

## Claims

1. A grounding arrangement for an electrical system, the grounding arrangement comprising:
a grounding strap connecting between a stationary wall and an opposed movable wall;
a flat grounding strap having opposing ends fixed to a grounding point on the stationary wall and the opposed movable wall, such that the strap flexes to accommodate movement of the movable wall relative to the stationary wall, and wherein the grounding strap is folded one or more times to accomplish the flexing, and wherein the grounding strap forms at least one vertex.

2. The grounding arrangement of claim 1, wherein the stationary wall comprises a wall of a chassis for a cable management panel.

3. The grounding arrangement of claim 1, wherein the opposed movable wall is a rear wall of a cable management drawer.

4. The grounding arrangement of claim 1, wherein the grounding strap is fastened to the stationary wall by a bolt, and wherein the bolt forms at least a portion of the grounding point.

5. The grounding arrangement of claim 4, wherein the grounding strap is fastened to the movable wall by a fastener, and wherein the fastener and the bolt are offset to reduce a minimum distance between the stationary wall and the opposed movable wall.

6. The grounding arrangement of claim 4, further comprising a support arranged to prevent pivotal movement of the grounding strap around an axis defined by the bolt.

7. The grounding arrangement of claim 6, wherein the support comprises mechanical bonding between the grounding strap and the stationary wall.

8. A flat grounding strap having first and second opposing ends and at least one vertex, the strap configured to flex to accommodate movement of the first opposing end relative to the second opposing end, and wherein the grounding strap is folded one or more times to form the vertex and to accomplish the flexing.

9. The flat grounding strap of claim 8, wherein the flat grounding strap is substantially rigid along at least one axis of movement.

10. The flat grounding strap of claim 8, further comprising one or more connection locations at each of the first and second opposing ends.

11. The flat grounding strap of claim 8, wherein the flat grounding strap is flexible between extended and compacted positions.

12. The flat grounding strap of claim 11, wherein, in the extended position, the flat grounding strap forms a wishbone shape defined by the first and second opposing ends and the at least one vertex.

13. A method for grounding movable electrical equipment, the method comprising:
connecting a flat grounding strap having first and second opposing ends to a grounding location and electrical equipment movable with respect to the grounding location, the first opposing end connecting to the grounding location and the second opposing end connecting to a grounding connection of the electrical equipment, the strap configured to flex to accommodate movement of the first opposing end relative to the second opposing end, and wherein the grounding strap is folded one or more times to accomplish the flexing, and wherein the grounding strap forms at least one vertex.

14. The method of claim 13, further comprising moving the electrical equipment away from the grounding location, thereby extending the flat grounding strap from a compacted position to an extended position.

15. The method of claim 14, wherein the grounding strap includes at least one vertex and, in the extended position, the flat grounding strap forms a wishbone shape defined by the first and second opposing ends and the at least one vertex.

16. The method of claim 14, further comprising moving the electrical equipment toward the grounding location, thereby compressing the flat grounding strap from the extended position to the compacted position.

17. The method of claim 13, wherein the electrical equipment is mounted within a drawer of a telecommunications system.

18. The method of claim 13, wherein the grounding point is located on a back surface of a chassis of a telecommunications panel.

19. The method of claim 13, wherein the electrical equipment forms a portion of an optical fiber distribution system.