Abstract:
An exemplary embodiment disclosed herein relates to a method of feeding cable through a wall. The method includes, cutting an outer jacket of a cable, and pulling the outer jacket away from the cut thereby exposing an electromagnetic interference shielding layer. The method further includes, clamping a conductor around the shielding layer, securing the clamped conductor to a conductive wall, and electrically connecting the clamped conductor to the conductive wall.

Description:
GOVERNMENT INTEREST 
       [0001]    This invention was made with Government support under contract No.: B517552 awarded by The Department of Energy. The Government has certain rights in this invention. 
         [0002]    IBM ® is a registered trademark of International Business Machines Corporation, Armonk, N.Y., U.S.A. Other names used herein may be registered trademarks, trademarks or product names of International Business Machines Corporation or other companies 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    Electromagnetic Interference or EMI is electromagnetic radiation which is emitted by electrical circuits carrying rapidly changing signals, as a by-product of their normal operation, and which causes unwanted signals (interference or noise) to be induced in other circuits. This interrupts, obstructs, or otherwise degrades or limits the effective performance of those other circuits. Electromagnetic Interference is also known as Radio Frequency Interference or RFI. 
         [0004]    Most countries have legal requirements that electronic and electrical hardware must still work correctly when subjected to certain amounts of EMI, and should not emit EMI which could interfere with other equipment (such as radios). 
         [0005]    One way to control or contain EMI within a device is to contain the entire electronic device in a conductive enclosure also known as a Faraday cage. Many electronic devices are contained in a single enclosure for which containing the EMI is more easily accomplished by either enclosure in a box made of conductive material or, by adding a conductive layer such as paint, to the inside of the enclosure. 
         [0006]    When electronic devices are contained in several different enclosures and are connected by one or more cables, containment of EMI can be difficult. The conductors in the cables may be wrapped in a conductive foil, such as aluminum, for example, or a braided conductor. Both the conductive foil and the braided conductor are known as shields. Effectively connecting the shield of each cable to each conductive enclosure, to which it is connected, in a cost effective system consuming a minimum amount of area around the cable to enclosure interface may be desirable in the art. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0007]    An exemplary embodiment disclosed herein relates to a method of feeding cable through a wall. The method includes, cutting an outer jacket of a cable, and pulling the outer jacket away from the cut thereby exposing an electromagnetic interference shielding layer. The method further includes, clamping a conductor around the shielding layer, securing the clamped conductor to a conductive wall, and electrically connecting the clamped conductor to the conductive wall. 
         [0008]    Further disclosed herein is an embodiment of a method of electromagnetic interference shielding a cable protruding through a wall of an enclosure. The method includes, circumferentially cutting a jacket radially outward of an electromagnetic interference shielding layer of the cable, and thereby exposing the shielding layer by sliding the jacket away from the circumferential cut. Further, clamping the circumference of the shielding layer with an electrically conductive clamp. And finally, electrically attaching the conductive clamp flush with a wall of an enclosure through which the cable is routed. 
         [0009]    Further disclosed herein relates to a system for electromagnetic interference (EMI) shielding a cable through an enclosure wall. The system includes, at least one cable with an electromagnetic shielding layer exposed by a circumferential cut through an outer jacket thereof, and at least one layer of conductive tape with conductive adhesive wrapped circumferentially around the exposed shielding layer. The system further includes, at least one electrically conductive clamp electrically connected to and clamped around the circumference of the tape wrapped cable, and an electrically conductive wall of an enclosure with an opening, the opening being receptive of the cable and the wall being receptive of the at least one conductive clamp. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0010]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0011]      FIG. 1  depicts a partial cross sectional view through a cable, clamp, and wall as disclosed herein; and 
           [0012]      FIG. 2  depicts a perspective view of several cables assembled through clamps and a wall as disclosed herein. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]    A detailed description of several embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figures. 
         [0014]    Referring to  FIG. 1  an exemplary embodiment disclosed herein of a cable to enclosure interface system is shown generally at  4 . A cable  10  includes a plurality of signal conductors  14  each with insulation  18  thereon. A ground wire  22  is coupled with a pair of signal conductors  14  and is encased by a signal shield  26  and a jacket  30  comprising a shielded pair  34 . A cable shield  38  and an outer jacket  42  encircle a plurality of shielded pairs  34  (only one pair is shown) to complete the construction of the cable  10 . Alternate cable constructions with an outer jacket and EMI shielding layer could also be employed within the scope and spirit of the present invention. 
         [0015]    The cable shield  38  minimizes EMI from escaping from the cable  10  or intruding into the cable  10  where it could interfere with the signals traveling through the signal conductors  14 . The maximum size of an opening in the shield  38  necessary to effectively block EMI depends on the frequency of the signals. Many computers today operate in the multiple-gigahertz range, and the maximum opening size at these frequencies is on the order of three or four millimeters. Cable shields  38  are frequently made of braided conductor such as aluminum or copper, for example, and are susceptible to damage when not protected by the outer jacket  42 . 
         [0016]    In an embodiment disclosed herein, a circumferential cut  46  through the outer jacket  42  is pulled back to expose a portion of the cable shield  38 . An option to prevent fraying of the shield  38 , which may have been inadvertently cut, during the cutting of the outer jacket  42 , for example, is to apply a layer of conductive tape  50  over the exposed shield  38 . Wrapping at least one full layer of conductive tape  50  around the exposed shield  38  should provide sufficient protection to the shield  38 . The conductive tape  50  makes electrical connection with the cable shield  38  to form an EMI shield therearound to minimize EMI leakage should an opening in the exposed shield  38  be formed. The tape  50  also presents a more professional and finished look as compared to the shield layer  38  without the tape  50 . Copper foil and metalized fabric are a few possible material choices for the tape  50 . The tape  50  may use an adhesive that is conductive to assist in establishing a good electrical connection between the shield  38  and the tape  50 . 
         [0017]    Referring to  FIG. 2  a plurality of cables  10  are shown passing through an opening in a wall  54  of an enclosure that contains an electrical circuit (not shown) to which the cables  10  are functionally attached. A pair of electrically conductive clamps  58  each comprising a first portion  62  and a second portion  66  are shown abutting the wall  54 . The first portions  62  and the second portions  66  each have a plurality of substantially semicircular grooves  70  that form a substantially circular hole  74  through the clamps  58  when the first portions  62  and the second portions  66  are clamped together. The hole  74  is sized to be slightly smaller in diameter than the diameter formed by the tape  50  around the shield  38  to thereby create a compressive force circumferentially therearound. The compressive force helps to complete the electrical connection between the clamps  58  and the tape  50  and to minimize the size of any openings that could allow EMI to leak therethrough. 
         [0018]    The first portion  62  and second portion  66  of the clamps  58  are held together by screws  78  that pass through clearance holes in the first portions  62  and threadably engage with tapped holes (not shown) in the second portions  66 . The two clamps  58  shown are reversed end to end from one another such that the screws  78  on one clamp  58  are directed inwardly towards the screws  78  on the other clamp  58 . This orientation allows the clamps  58  to lie flush together at the surfaces where they meet. Alternate embodiments may be employed to fasten the first portion  62  and second portion  66  together such as adhesive bonding or click tabs with windows, for example. Additionally, alternate embodiments could clamp any number of cables in any number of rows and columns. 
         [0019]    After the screws  78  of the clamps  58  are tightened the outer jacket  42  can be pushed towards the clamps  58  until the outer jacket  42  butts against a surface  80  of the clamp  58  from which the cable  10  extends. Similarly on the opposite side of the clamp  58  the outer jacket  42  can be butted against the surface  80  thereon. Next the clamps  58  are attached to the wall  54 . A cable  82  on the wall  54  side of the clamps  58  are fed through openings  84  in the wall  54  until the surfaces  80  of the clamps  54  are flush against the wall  54 . Screws  86  protrude through holes  88  in tabs  90  that extend from both ends of the clamps  58  and threadably engage with holes  89  in the wall  54 . In addition to mechanically securing the clamps  58  to the wall  54 , the screws  86  also complete an electrical circuit that includes the wall  54 , the screws  86 , the clamps  58 , the conductive tape  50 , tape adhesive, and EMI shielding  38 . By electrically connecting all these components to one another and limiting the size of any openings between them, the cables  10  to wall  54  connections disclosed herein effectively shield the signal conductors  14  within the cable  10  from external EMI, as well as preventing the signal conductors  14  from transmitting potentially damaging EMI energy into the environment. 
         [0020]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.