Abstract:
A conductive shield contact including a plurality of fingers formed in a partial circle for contacting a cable shield, the fingers being separate elements, each finger having a first end and a second end. A partial circular member is positioned at a second end of the fingers and is connected to the fingers. A tab is formed for contacting a conductive portion of a connector to establish an electrical path between the cable shield and the conductive portion of the connector.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional patent application, Ser. No. 60/523,440 filed Nov. 19, 2003, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     Existing cable shield contacts are known.  FIG. 1  illustrates a perspective view of an existing assembled plug, shown generally as  100 . The plug  100  is similar to plugs in U.S. Pat. No. 6,358,091, the entire contents of which are incorporated herein by reference. The plug  100  includes a top cover  102 , a bottom cover  104  and a core  106 . The top cover  102 , bottom cover  104  and core  106  are all conductive to provide shielding as described herein. These conductive components may be made from metal, metallized plastic or any other known conductive material. Core  106  supports insulative (e.g. plastic) contact carriers  108 . Each contact carrier  108  includes two contacts  160  defining a pair. A boot  112  provides strain relief and is made from a pliable plastic or rubber. Also shown in  FIG. 1  is cable  10  entering boot  112 . A latch  114  is provided on the top cover  102  for coupling the plug  100  to outlet (not shown). 
       FIG. 2  is an exploded, perspective view of the top cover  102 . The top cover includes a shield contact  164  that electrically connects the ground layer of cable  10  to the plug core  106 . Shield contact  164  is conductive and is preferably made from metal. Shield contact  164  has an arcuate portion  166  formed to generally follow the shape of cable  10 . Arcuate portion  166  includes barbs  168  that pierce the ground layer of cable  10  and the cable jacket. This electrically and mechanically connects the shield contact  164  to cable  10 . Shield contact  164  includes a pad  170  having two openings  172  formed therein for receiving two posts  176  formed in top cover  102 . The friction fit between posts  176  and openings  172  secures the shield contact  164  to top cover  102 . A tab  174  extends away from pad  170  and contacts the plug core  106 . A channel  178  is formed in the top cover  102  for receiving central ridge  144  on plug core  106 . 
       FIG. 3  is an exploded, perspective view of the bottom cover  104 . Bottom cover  104  is similar to top cover  102  in that both use shield contact  164  in the same manner. 
     In addition,  FIG. 4  illustrates a graph of the calculated transfer impedance of the shield contact  164 . The dashed line illustrates the limit of the transfer impedance. 
     Other existing shield connection consist of single or double bar type contacts that contacted a minimal amount of cable shield area due to the non-uniform geometry of the cable and shield in the terminated state. Other solutions include U.S. Pat. No. 5,372,513 that includes an arcuate cable engagement section  122 . The same manufacturer has produced a cable engagement ground clip having a planar tab, divided into separate, planar fingers. Specifications are demanding better transfer impedance and coupling attenuation performance than existing designs provide. 
     SUMMARY OF THE INVENTION 
     The above-discussed and other drawbacks and deficiencies of the prior art are overcome or alleviated by a cable shield contact. A conductive shield contact including a plurality of fingers formed in a partial circle for contacting a cable shield, the fingers being separate elements, each finger having a first end and a second end. A partial circular member is positioned at a second end of the fingers and is connected to the fingers. A tab is formed for contacting a conductive portion of a connector to establish an electrical path between the cable shield and the conductive portion of the connector. 
     The above-discussed and other features and advantages of the present invention will be appreciated and understood by those skilled in the art from the following detailed description and drawings. 
    
    
     
       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 an existing assembled plug; 
         FIG. 2  is an exploded, perspective view of the plug top cover of  FIG. 1 ; 
         FIG. 3  is an exploded, perspective view of the plug bottom cover of  FIG. 1 ; 
         FIG. 4  is a graph of the calculated transfer impedance of the shield contact of  FIG. 1 ; 
         FIG. 5  is a front perspective view of a cable shield contact for a connector; 
         FIG. 6  is a bottom view of the shield contact of  FIG. 5 ; 
         FIG. 7  is a graph of the calculated transfer impedance of the shield contact of  FIG. 5 ; and 
         FIG. 8  depicts an exemplary cable for use with the shield contact of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 5  illustrates a cable shield contact  200  that can be incorporated into any existing connector (e.g., plug, outlet, etc.) and in particular into a top cover and a bottom cover of the plug, such as shown in the existing plug  100  (see  FIGS. 1–3 ). Shield contact  200  is conductive and is preferably made from metal. Shield contact  200  has a plurality of fingers  202  that are formed around a diameter of a cable (not shown).  FIG. 5  illustrates an exemplary embodiment of the fingers arranged in a semi-circle contacting about 180 degrees of the cable shield. The fingers  202  generally follow the shape of the cable. The fingers can also be arranged so as to cover a quarter of a diameter of the cable or about 90 degrees of the cable shield. Embodiments of the invention are not limited to specific radial coverage of the fingers and exemplary embodiments may have fingers arranged radially from about 90 degrees to about 180 degrees. The cable shield contact  200  improves as the fingers  202  cover more of the cable shield. 
     The plurality of fingers  202  have a first end  204  and a second end  206 . A cross-section  208  of the plurality of fingers at the first end  204  is smaller than a cross-section  210  of the plurality of fingers at the second end  206  and at member  212 . The smaller cross-section  208  provides a gripping action to the cable shield  254  ( FIG. 8 ) and may be smaller that the cross-section of the cable shield. This smaller cross-section at the first end of the fingers  202  results in a spring pressure being applied by the fingers to the cable shield. The first end  204  of the plurality of fingers  202  may be lanced to provide improved gripping action. In other words, the first end of the fingers are bent outward away from the centerline to form finger tips  203  that will be tangential to the outside surface of the cable shield when the cable is positioned between fingers  202 . 
     The plurality of fingers  202  are held together at the second end  206  by a member  212 . In an exemplary embodiment, member  212  is a semi-circle member that also surrounds the cable. However, member  212  can be any type of member  212  that can hold the plurality of fingers together at the second end. 
     In addition, the plurality of fingers  202  can move individually, which allows for individual contacts to form around the cable shield and also allows for varying surface height and contact areas. Each finger  202  is free to move up or down to contact the cable shield providing a more reliable and less resistive connection. 
     The fingers  202  may be inserted under the insulative, outer jacket of the cable to make electrical and physical contact with the cable shield. Alternatively, the outer jacket of the cable may be removed exposing the cable shield. The cable shield may then be peeled back over the cable jacket. The fingers  202  are then placed in physical and electrical contact with the cable shield. Tab  174  contacts connector core  106  in a similar manner as described in U.S. Pat. No. 6,358,091. 
       FIG. 8  depicts an exemplary cable  250  for use with shield contact  200 . The cable  250  includes an insulative jacket and a conductive shield  254  positioned beneath the insulative jacket  252 . The conductive shield  254  may be a braid, a foil, or another conductive material. As described above, apportion of the jacket  252  may be removed, as shown in  FIG. 8 , and the finger tips  203  contact the conductive shield  254 . Alternatively, the jacket  252  may extend to the end of conduct shield  254 . In this embodiment, the fingers  202  are positioned beneath the jacket  252  and in contact with the conductive shield  254 . 
     The advantage of the shield contact  200  is that it provides a low resistance path from the cable shield (not shown) to the next physical ground path on a connector. This could be a connector shield, connecting block shield, patch panel, cable outlet box ground tab or coupler, etc. The term connector is used in a generic fashion to encompass a variety of components. In addition, the shield contact requires no additional tools and allows for different diameter cables and shield materials (foil vs. braid). Maintaining proper ground requires maintaining a low resistance connection from one point of the ground circuit to the next. If the ground path is a cable shield, when that cable is cut into to terminate to a connector, the connection of the shield to this next physical path must be low in resistance. The shield in the cable and other devices is required to maintain safe passage for high current faults as well as to provide electric immunity and electro magnetic compatibility. In other words the shield protects the internal items of the cable (electrical transmission wires) from outside electrical interference and it protects anything near the cable from electromagnetic energy emitted by the internal transmission wires. A breakdown of the path can result in excessive electrical noise being radiated outward, therefore affecting nearby electronics or it could allow outside electrical interference to penetrate into the cable and corrupt the signal on the internal transmission wires. The shield contact  200  provides a repeatable and user-friendly field termination method for cables that result in a low resistance connection to the cable shield. 
     The improved transfer impedance of the shield contact  200  is illustrated in  FIG. 7 . There is improved electrical immunity as shown by the transfer impedance testing, which measures how well the shield terminations perform in a cable and connector. The ability to contact more of the cable shield area results in a lower contact resistance and lower conducting path for currents. Present designs for field terminable products cannot conform to the uneven surface areas involved. The fingers  202  contact the cable shield  254  and float independently from each other, which allows the shield contact  200  to conform more easily to the different surface characteristics of the cable shield. This allows more areas of contact and hence lower resistance. This design can also work for a range of cable sizes and can be incorporated in to a housing design to eliminate parts. Moreover, the shield contact  200  requires no special tool when inserting the cable to the plug. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.