Patent Publication Number: US-8991045-B2

Title: Grounding arrangement and method for a shielded cable

Description:
TECHNICAL FIELD OF INVENTION 
     The present invention relates to a shielded cable; more particularly to a grounding arrangement for the shielded cable, and still even more particularly to a method for forming the grounding arrangement on the shielded cable. 
     BACKGROUND OF INVENTION 
     Cables are known for transmitting electrical current and/or signals from a first to device to a second device. In an example shown in U.S. Pat. No. 7,598,455 on Oct. 6, 2009 to Gump et al., a shielded cable includes a conductive core surrounded by a core insulation layer to electrically insulate the conductive core. The core insulation layer is surrounded by a conductive shield layer in the form of a metallic braid that is woven around the core insulation layer in order to shield any electronic devices in the vicinity of the cable from electromagnetic interference (EMI) caused by electric current flowing through the conductive core. An outer insulation layer surrounds the conductive shield layer. The end of the cable is cut circumferentially at three axial spaced locations with the cuts being successively deeper in order to expose lengths of the conductive core, core insulation layer, and conductive shield layer. In order to ground the conductive shield layer, an annular inner ferrule is disposed between the core insulation layer and the exposed portion of the conductive shield layer and an annular outer ferrule is disposed around the exposed portion of the conductive shield layer and crimped thereto, thereby capturing the conductive shield layer between the inner ferrule and the outer ferrule. The inner ferrule and outer ferrule are loose-piece and are manufactured using deep drawing or machining processes, thereby requiring the inner ferrule and outer ferrule to be manually assembled to the cable. 
     U.S. Pat. No. 3,538,239 to Henshaw on Nov. 3, 1970 teaches an inner and outer ferrule for a shielded cable where the inner ferrule and outer ferrule are connected together by a strap and integrally formed together from sheet metal where the inner ferrule is formed into an annular shape and the outer ferrule is formed into a U-shape prior to the inner ferrule and outer ferrule being applied to the shielded cable. While this inner and outer ferrule arrangement may allow manufacture of the inner ferrule and the outer ferrule to be to be automated, it may be difficult to position the inner ferrule between the core insulation layer and the conductive shield layer. Furthermore, the inner ferrule being formed into an annular shape prior to being assembled to the shielded cable limits its use to a single gauge size of wire. 
     What is needed is a grounding arrangement for a shielded cable which minimizes or eliminates one or more of the shortcomings as set forth above. 
     SUMMARY OF THE INVENTION 
     Briefly described, a method is provided for forming a grounding arrangement on a shielded cable which includes a conductive core, a core insulation layer radially surrounding the conductive core, a conductive shield layer radially surrounding the core insulation layer, and an outer insulation layer radially surrounding the conductive shield layer. The method includes removing a length of the outer insulation layer to expose an end portion of the conductive shield layer. An inner ferrule is provided which is configured to be crimped around the shielded cable. The inner ferrule is positioned adjacent to the end portion of the conductive shield layer that has been exposed, the inner ferrule is crimped around the core insulation layer, and the end portion of the conductive shield layer is folded over the inner ferrule to radially surround the inner ferrule. An electrically conductive outer ferrule is provided which is configured to be crimped around the inner ferrule. The outer ferrule is positioned radially adjacent to the end portion of the conductive shield layer that has been positioned to radially surround the inner ferrule and the outer ferrule is crimped radially around the inner ferrule to capture the end portion of the conductive shield layer radially between the inner ferrule and the outer ferrule, thereby fixing the outer ferrule in electrical contact with the conductive shield layer. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       This invention will be further described with reference to the accompanying drawings in which: 
         FIG. 1  is an isometric exploded view of a shielded cable with a grounding arrangement in accordance the present invention; 
         FIG. 2  is an isometric view of an inner ferrule of the grounding arrangement in accordance with the present invention prior to being assembled to the shielded cable; 
         FIG. 3  is an isometric view of an outer ferrule of the grounding arrangement in accordance with the present invention prior to be assembled to the shielded cable; 
         FIG. 4  is an isometric view of the shielded cable of  FIG. 1  prepared to receive the grounding arrangement of the present invention in a method of a first embodiment; 
         FIG. 5  is an isometric view of the shielded cable of  FIG. 4  with the inner ferrule of  FIG. 2  positioned adjacent to a conductive shield layer of the shielded cable; 
         FIG. 6  is an isometric view of the shielded cable of  FIG. 5  with the inner ferrule crimped around the conductive shield layer; 
         FIG. 7  is an isometric view of the shielded cable of  FIG. 6  with the conductive shield layer positioned over the inner ferrule; 
         FIG. 8  is an isometric view of the shielded cable of  FIG. 7  with the outer ferrule of  FIG. 3  positioned adjacent to the conductive shield layer; 
         FIG. 9  is an isometric view of the shielded cable of  FIG. 8  with the outer ferrule crimped around the conductive shield layer; 
         FIG. 10  is an isometric view of the shielded cable of  FIG. 1  prepared to receive the grounding arrangement of the present invention in a method of a second embodiment; 
         FIG. 11  is an isometric view of the shielded cable of  FIG. 10  with a conductive shielded layer of the shielded cable folded backward over an outer insulation layer; 
         FIG. 12  is an isometric view of the shielded cable of  FIG. 11  with the inner ferrule of  FIG. 2  positioned adjacent to the conductive shield layer of the shielded cable; 
         FIG. 13  is an isometric view of the shielded cable of  FIG. 12  with the inner ferrule crimped around a core insulation layer of the shielded cable; 
         FIG. 14  is an isometric view of the shielded cable of  FIG. 13  with the conductive shield layer positioned over the inner ferrule; 
         FIG. 15  is an isometric view of the shielded cable of  FIG. 14  with the outer ferrule of  FIG. 3  positioned adjacent to the conductive shield layer; 
         FIG. 16  is an isometric view of the shielded cable of  FIG. 15  with the outer ferrule crimped around the conductive shield layer; 
         FIG. 17  is an isometric view of a bypass wing arrangement; and 
         FIG. 18  is the bypass wing arrangement of  FIG. 17  shown crimped onto a cable. 
     
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Referring to  FIG. 1 , an exploded isometric view of a shielded cable  10  is shown which has been prepared to receive a grounding arrangement  12 . Shielded cable  10  includes a conductive core  14  extending along a shielded cable axis  16 , a core insulation layer  18  coaxially and radially surrounding conductive core  14 , a conductive shield layer  20  coaxially and radially surrounding core insulation layer  18 , and an outer insulation layer  22  coaxially and radially surrounding conductive shield layer  20 . Conductive core  14  is a metallic material, for example only, copper, aluminum, alloys thereof, or any other metallic material suitable for conducting electricity. Core insulation layer  18  and outer insulation layer  22  are made of an electrically insulative material. Conductive shield layer  20  is a metallic material, for example only, braided metal wire woven around core insulation layer  18  that is suitable for conducting electricity. Conductive shield layer  20  may shield electronic devices in the vicinity of shielded cable  10  from EMI caused by electric current flowing through conductive core  14 . 
     With continued reference to  FIG. 1  and with additional reference to  FIGS. 4 and 10 , shielded cable  10  has been prepared to receive grounding arrangement  12  by cutting the end portion of shielded cable  10  in three axially spaced locations with each cut being successively deeper so that a portion of outer insulation layer  22  may be removed to expose an end portion of conductive shield layer  20 , a portion of conductive shield layer  20  may be removed to expose core insulation layer  18 , and a portion of core insulation layer  18  may be removed to expose conductive core  14 . The portions of outer insulation layer  22 , conductive shield layer  20 , and core insulation layer  18  that are removed are illustrated as phantom lines in  FIG. 1 . 
     With continued reference to  FIG. 1  and with additional reference to  FIGS. 2 and 3 , grounding arrangement  12  includes an inner ferrule  24  configured to be crimped around core insulation layer  18  and an outer ferrule  26  configured to be crimped around inner ferrule  24 . Inner ferrule  24  includes an inner ferrule base portion  28 , a first inner ferrule crimp wing  30  and a second inner ferrule crimp wing  32 . First inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  extend from opposing sides of inner ferrule base portion  28  such that inner ferrule  24  may be substantially V-shaped or U-shaped as shown in  FIGS. 1 and 2  prior to assembly of inner ferrule  24  to shielded cable  10 . Inner ferrule base portion  28  may be arcuate in shape as shown. First inner ferrule crimp wing  30  is attached at one end to inner ferrule base portion  28  while the other end is free and defines a first inner ferrule crimp wing free end  34 . Similarly, second inner ferrule crimp wing  32  is attached at one end to inner ferrule base portion  28  while the other end is free and defines a second inner ferrule crimp wing free end  36 . Inner ferrule  24  may be formed from a sheet of electrically conductive sheet stock by conventional metal forming techniques such as punching and stamping. As shown in  FIG. 2 , inner ferrule  24  may be formed with an inner ferrule carrier strip  38  and connected thereto with an inner ferrule carrier connecting strap  40 . While not shown, inner ferrule carrier strip  38  may include a plurality of inner ferrules  24  in order to facilitate automated production of inner ferrules  24  and also to facilitate automated assembly of inner ferrule  24  to shielded cable  10 . Assembly of inner ferrule  24  to shielded cable  10  will be discussed in detail later. 
     Outer ferrule  26  includes an outer ferrule to cable attachment section  42  and may include an outer ferrule grounding section  44 . Outer ferrule to cable attachment section  42  includes an outer ferrule to cable attachment section base portion  46 , a first outer ferrule crimp wing  48  and a second outer ferrule crimp wing  50 . First outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  extend from opposing sides of outer ferrule to cable attachment section base portion  46  such that outer ferrule to cable attachment section  42  may be substantially V-shaped or U-shaped as shown in  FIGS. 1 and 3  prior to assembly of outer ferrule  26  to shielded cable  10 . Outer ferrule to cable attachment section base portion  46  may be arcuate in shape as shown. First outer ferrule crimp wing  48  is attached at one end to outer ferrule to cable attachment section base portion  46  while the other end is free and defines a first outer ferrule crimp wing free end  52 . Similarly, second outer ferrule crimp wing  50  is attached at one end to outer ferrule to cable attachment section base portion  46  while the other end is free and defines a second outer ferrule crimp wing free end  54 . 
     Outer ferrule grounding section  44  includes an outer ferrule grounding section base portion  56 , a first outer ferrule grounding wing  58 , and a second outer ferrule grounding wing  60 . First outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  extend from opposing sides of outer ferrule grounding section base portion  56  such that outer ferrule grounding section  44  may be substantially V-shaped or U-shaped as shown in  FIGS. 1 and 3  prior to assembly of outer ferrule  26  to shielded cable  10 . Outer ferrule grounding section base portion  56  may be arcuate in shape as shown. First outer ferrule grounding wing  58  is attached at one end to outer ferrule grounding section base portion  56  while the other end is free and defines a first outer ferrule grounding wing free end  62 . Similarly, second outer ferrule grounding wing  60  is attached at one end to outer ferrule grounding section base portion  56  while the other end is free and defines a second outer ferrule grounding wing free end  64 . Outer ferrule grounding section  44  is linked to outer ferrule to cable attachment section  42  by an outer ferrule linking strap  66 . Outer ferrule grounding section  44  is provided for connection to ground or a conductor connected to ground, thereby grounding conductive shield layer  20 . While outer ferrule grounding section  44  has been illustrated and described, outer ferrule grounding section  44  may be omitted. If outer ferrule grounding section  44  is omitted, outer ferrule to cable attachment section  42  is connected directly to ground or directly to a conductor connected to ground, thereby grounding conductive shield layer  20 . 
     Outer ferrule  26  may be formed from a sheet of electrically conductive sheet stock by conventional metal forming techniques such as punching and stamping. As shown in  FIG. 3 , outer ferrule  26  may be formed with an outer ferrule carrier strip  68  and connected thereto with an outer ferrule carrier connecting strap  70 . While not shown, outer ferrule carrier strip  68  may include a plurality of outer ferrules  26  in order to facilitate automated production of outer ferrules  26  and also to facilitate automated assembly of outer ferrule  26  to shielded cable  10 . Assembly of outer ferrule  26  to shielded cable  10  will be discussed in detail later. 
     A first embodiment of assembling grounding arrangement  12  to shielded cable  10  will now be discussed with continued reference to  FIG. 1  and with additional reference to  FIGS. 4-9 . As shown in  FIG. 4 , shielded cable  10  has been prepared as previously described in order to receive grounding arrangement  12 . After shielded cable  10  has been prepared to receive grounding arrangement  12 , inner ferrule  24  is positioned adjacent to the end portion of conductive shield layer  20  that has been exposed by removing a length of outer insulation layer  22  as shown in  FIG. 5 . Inner ferrule  24  is also positioned to axially abut or to be axially proximal to outer insulation layer  22 . When inner ferrule  24  is positioned adjacent to conductive shield layer  20 , conductive shield layer  20  extends axially beyond inner ferrule  24  toward the portion of conductive core  14  that has been exposed. 
     First inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  are then crimped or deformed around conductive shield layer  20  as shown in  FIG. 6 , thereby fixing inner ferrule  24  to shielded cable  10 . It should be noted that since conductive shield layer  20  radially surrounds core insulation layer  18 , the step of crimping or deforming first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  around conductive shield layer  20  also crimps or deforms first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  around core insulation layer  18 . Inner ferrule carrier strip  38  may be removed from inner ferrule  24  in the same step that crimps or deforms first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  around conductive shield layer  20 . 
     After inner ferrule  24  has been fixed to shielded cable  10 , conductive shield layer  20  is positioned to radially surround inner ferrule  24  as shown in  FIG. 7 . Conductive shield layer  20  is positioned to radially surround inner ferrule  24  by folding conductive shield layer  20  backward over inner ferrule  24 . It should be noted that inner ferrule  24  is obscured by conductive shield layer  20  in  FIGS. 7-9  because conductive shield layer  20  now radially surrounds inner ferrule  24 . 
     After conductive shield layer  20  is positioned radially outward of inner ferrule  24 , outer ferrule  26  is positioned relative to shielded cable  10  such that outer ferrule to cable attachment section  42  is radially adjacent to the portion of conductive shield layer  20  that is positioned radially outward of inner ferrule  24  and such that outer ferrule grounding section  44  is radially outward of outer insulation layer  22  as shown in  FIG. 8 . As shown, outer ferrule to cable attachment section  42  may axially abut or may be axially proximal to outer insulation layer  22 . 
     After outer ferrule  26  has been positioned relative to shielded cable  10  as shown in  FIG. 8 , first outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  are crimped or deformed around conductive shield layer  20  as shown in  FIG. 9 , thereby fixing outer ferrule  26  to shielded cable  10 . In this way, conductive shield layer  20  is captured and clamped securely radially between inner ferrule  24  and outer ferrule to cable attachment section  42  of outer ferrule  26 , thereby ensuring a good electrically conductive interface between conductive shield layer  20  and outer ferrule  26 . It should be noted that the majority of conductive shield layer  20  is obscured in  FIG. 9  because outer ferrule to cable attachment section  42  now radially surrounds conductive shield layer  20 . 
     First outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  may be crimped or deformed around outer insulation layer  22  as shown in  FIG. 9  at the same time that first outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  are crimped or deformed around conductive shield layer  20 . First outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  may be crimped or deformed around outer insulation layer  22  to either grip outer insulation layer  22  tightly or alternatively an annular space may be formed between outer ferrule grounding section  44  and outer insulation layer  22 . Outer ferrule carrier strip  68  may be removed from outer ferrule  26  in the same step that crimps or deforms first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  around conductive shield layer  20  and first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  around outer insulation layer  22 . It should be noted that first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  may alternatively be crimped or deformed around outer insulation layer  22  either before or after first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  are crimped or deformed around conductive shield layer  20 . 
     A second embodiment of assembling grounding arrangement  12  to shielded cable  10  will now be discussed with reference to  FIGS. 10-16 . As shown in  FIG. 10 , shielded cable  10  has been prepared as previously described in order to receive grounding arrangement  12 . Next, as shown in  FIG. 11 , the end portion of conductive shield layer  20  that has been exposed is folded backward over outer insulation layer  22 . After conductive shield layer  20  has been folded backward over outer insulation layer  22 , inner ferrule  24  is positioned adjacent to the portion of core insulation layer  18  that has been exposed by folding conductive shield layer  20  backward over outer insulation layer  22  as shown in  FIG. 12 . Inner ferrule  24  is also positioned axially adjacent to conductive shield layer  20  by axially abutting or being axially proximal to conductive shield layer  20 . When inner ferrule  24  is positioned adjacent to core insulation layer  18  and conductive shield layer  20 , core insulation layer  18  extends axially beyond inner ferrule  24  toward the portion of conductive core  14  that has been exposed. 
     First inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  are then crimped or deformed around core insulation layer  18  as shown in  FIG. 13 , thereby fixing inner ferrule  24  to shielded cable  10 . Inner ferrule carrier strip  38  may be removed from inner ferrule  24  in the same step that crimps or deforms first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  around core insulation layer  18 . 
     After inner ferrule  24  has been fixed to shielded cable  10 , conductive shield layer  20  is positioned to radially surround inner ferrule  24  as shown in  FIG. 14 . Conductive shield layer  20  is positioned to radially surround inner ferrule  24  by folding conductive shield layer  20  forward over inner ferrule  24  as shown in  FIG. 14 . It should be noted that inner ferrule  24  is obscured by conductive shield layer  20  in  FIGS. 14-16  because conductive shield layer  20  radially surrounds inner ferrule  24 . 
     After conductive shield layer  20  is positioned to radially surround inner ferrule  24 , outer ferrule  26  is positioned relative to shielded cable  10  such that outer ferrule to cable attachment section  42  is radially adjacent to the portion of conductive shield layer  20  that is positioned radially outward of inner ferrule  24  and such that outer ferrule grounding section  44  is radially outward of outer insulation layer  22  as shown in  FIG. 15 . As shown, outer ferrule to cable attachment section  42  may axially abut or may be axially proximal to outer insulation layer  22 . 
     After outer ferrule  26  has been positioned relative to shielded cable  10  as shown in  FIG. 15 , first outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  are crimped or deformed around conductive shield layer  20  as shown in  FIG. 16 , thereby fixing outer ferrule  26  to shielded cable  10 . In this way, conductive shield layer  20  is captured and clamped securely radially between inner ferrule  24  and outer ferrule to cable attachment section  42  of outer ferrule  26 , thereby ensuring a good electrically conductive interface between conductive shield layer  20  and outer ferrule  26 . It should be noted that the majority of conductive shield layer  20  is obscured in  FIG. 16  because outer ferrule to cable attachment section  42  now radially surrounds conductive shield layer  20 . 
     First outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  may crimped or deformed around outer insulation layer  22  as shown in  FIG. 16  at the same time that first outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  are crimped or deformed around conductive shield layer  20 . First outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  may be crimped or deformed around outer insulation layer  22  to either grip outer insulation layer  22  tightly or alternatively an annular space may be formed between outer ferrule grounding section  44  and outer insulation layer  22 . Outer ferrule carrier strip  68  may be removed from outer ferrule  26  in the same step that crimps or deforms first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  around conductive shield layer  20  and first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  around outer insulation layer  22 . It should be noted that first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  may alternatively be crimped or deformed around outer insulation layer  22  either before or after first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  are crimped or deformed around conductive shield layer  20 . 
     First inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  have been illustrated as rectangular in shape such that when first inner ferrule crimp wing  30  and second inner ferrule crimp wing  32  have been crimped or deformed, first inner ferrule crimp wing free end  34  and second inner ferrule crimp wing free end  36  are adjacent to each other. Similarly, first outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  have been illustrated as rectangular in shape such that when first outer ferrule crimp wing  48  and second outer ferrule crimp wing  50  have been crimped or deformed, first outer ferrule crimp wing free end  52  and second outer ferrule crimp wing free end  54  are adjacent to each other. Also similarly, first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  have been illustrated as rectangular in shape such that when first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60  are deformed around outer insulation layer  22 , first outer ferrule grounding wing free end  62  and second outer ferrule grounding wing free end  64  are adjacent to each other. It should now be understood that the crimp wings and ground wings may be formed in other shapes. Similarly, it should now be understood that different numbers of crimp wings and ground wings may be included.  FIGS. 17 and 18  illustrate a bypass wing arrangement with a first bypass wing  72  and a second bypass wing  74  which are each formed as triangles. As can be seen, the triangular nature of first bypass wing  72  and second bypass wing  74  allow the bypass wings to bypass each other, thereby preventing first bypass wing  72  from contacting second bypass wing  74 . The triangular nature of first bypass wing  72  and second bypass wing  74  thereby allows different gauge wires to be used with the same ferrule while still allowing first bypass wing  72  and second bypass wing  74  to sufficiently radially surround the cable. First bypass wing  72  and second bypass wing  74  may be used in the place of any or all of first inner ferrule crimp wing  30 , second inner ferrule crimp wing  32 , first outer ferrule crimp wing  48 , second outer ferrule crimp wing  50 , first outer ferrule grounding wing  58  and second outer ferrule grounding wing  60 . 
     Grounding arrangement  12  allows for reduced costs by producing inner ferrule  24  and outer ferrule  26  by punching and stamping of sheet stock rather than by forming individual loose pieces. Plating of inner ferrule  24  and outer ferrule  26  can therefore be performed on the sheet stock rather than on individual loose pieces. Furthermore, since the wings of the ferrules are made by stamping, they can be designed to accommodate multiple sizes of cable. The methods disclosed herein for attaching grounding arrangement  12  to shielded cable  10  allows inner ferrule  24  and outer ferrule  26  to be more easily and more quickly attached to shielded cable  10 , thereby reducing production time and costs. 
     While not shown, it should be understood that a cable terminal may be placed in electrical communication with conductive core  14  in conventional fashion in order to interface with a mating terminal of, for example only, an electrical device or an electrical connector. 
     While this invention has been described in terms of preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.