US 3546365 A
Description (OCR text may contain errors)
47, 71, 74, 75, 75.2, 78, 84.1, 88.2, 90, 94; 339/14, 95-98, 223, 276, 100; 24/123(W), 129(W); 29/628, 630(A), 630(F); 16/108, 109
0 United States Patent 1111 3,546,365
 Inventor John Covell Collier  References Cited Flrnwwth, d- UNITED STATES PATENTS P 969 2,367,175 1/1945 Hahn 174/75 [221 2,536,003 12/1950 Dupre 174/75x M: 2,691,198 10/1954 Flood 24/123 July 2,8l4,026 11/1957 Broske 339/97x t 242,973 2,901,528 8/1959 Lazar 174/75 0 93 3,064,072 11/1962 Grafietal... 33'9/223x 14 1 Patented Dec-8,1970 3,078,436 2/1963 Berry 174/ssux 1 Awsnee AMP m 3,109,052 10/1963 Dumire etal. 174/88 [321 P ,t gg g g tfl 3,138,658 6/1964 Weimer,.lr. 174/s4x r1or1 y  Gm Brim FOREIGN eAreNrs 3 4 0 5 1 5,585 1894 Great Brltam 339/100 Primary Examiner- Laramie E. Askin Attorneys-Curtis, Morris and Safford, Marshall M.  GROUNDING CONNECTOR FOR CONNECTION Holcombe, W1ll1am Hmtze, W1ll1am J. Keatmg, Frederick ONTO A SHIELD or A counuc'ron MEANS Ram"; and "opkms 7 Claims, 6 Drawing Figs.
 U.S.(l 174/78, ABSTRACT: A trough-shaped metal ferrule comprises in- 29/628, 174/75, 339/276 wardly directed lances disposed in staggered relationship so [51 Int. Cl. ..L H0lr 5/08 that when the ferrule is crimped into position onto a shield of a [50} Field Search 174/35(C), coaxial cable the lances are embedded in the shield without penetrating the insulation under the shield and a grounding wire disposed between the ferrule and the shield is formed into a serpentine configuration around respective lances.
GROUNDING CONNECTOR FOR CONNECTION ONTO A SHIELD OF A CONDUCTOR MEANS This application is a continuation of my earlier application Ser. No. 750,423, filed July 24, 1968, now abandoned, which in turn is a continuation of my earlier application Ser. No, 242,973, filed Dec. 7, 1962, now abandoned.
This invention relates to electrical connection to the shield of an electrical conductor having a conductive core and a surrounding conductive shield separated by an intermediate layer of insulating material. To prevent undesired voltages from being induced in an electrical lead it is common practice to surround the core with an electrically conductive shield, for example, of copper braid, a layer of insulating material being interposed between the core and the shield. For effective shielding the shield is generally connected to ground by way of the chassis of an electrical apparatus containing the lead.
Although it is known to crimp a metal ferrule which is adapted to be'ground'ed by way of a tab on the ferrule or by a ground wire, to a stripped portion of a conductor shield, the connection between the ferrule and the shield may have a short useful life due to loss of shield resilience within the ferrule. If it is sought to remedy this defect by increasing the crimping pressure applied to the ferrule, the readily deformable insulating layer, for example of polyethylene, may be extruded from the ferrule and undesirably decrease the thickness of the insulating layer.
In an electrical connection between the shield of an electrical conductor having an electrically conductive core and between the core and the shield a layer of insulating material, and a ferrule crimped about the shield, according to the invention, the ferrule is formed with perforations each surrounded internally of the ferrule with lance means keying into the shield without penetrating the layer of insulating material. Suitably the lance means are provided by perforatingthe ferrule with a punch and pushing up the ferrule metal, the lances not being long enough to perforate or cut the shield which generally will be of braided form.
The invention also includes a ferrule-forming member for a connection according to the invention, which is of troughlike form and the base of the trough is formed with perforations, each surrounded internally of the trough with lance means pushed up from the ferrule-metal, Preferably the lance means around each perforation converge inwardly of the trough and advantageously the ferrule-forming member is so perforated that a plurality of lances are pushed up around each perforation,
In a method of forming lances in a ferrule-forming member according to the invention, punch means are forced through a metal blank to perforate the blank and push up the metal around the perforations on one side of'the blank and define lance means around respective perforations.
The perforations are preferably made in successive batches to avoid interference between the punch means employed.
The invention will now be described by way of example, with reference to the accompanying, partly diagrammatic drawings, in which:
FIG. I is a plan view ofa ferrule-forming blank;
FIG. 2 is an end elevation of the blank of FIG. I viewed from the left-hand side of that FIG.;
FIG. 3 is a perspective view of a troughlike ferrule-forming member; FIG. 4 is a side elevation ofa braid-shielded conductor with a ground;
FIG. Sis a rear side view of the conductor of FIG. 4; and
FIG. 6 is a perspective view of a braid-shielded conductor with a modified braid termination.
The blank of FIGS. land 2 comprises a thin, flat, metal plate member 1, for example of brass, ofgenerally rectangular form having at one edge a V-shaped recess 2 and at the opposite edge a complementary V-shaped projection 3. The recess 2 and the projection 3 extend between the other pair of opposite edges the plate member I. A series of punched perforations 4 is formed in the plate 1, as seen in 2, the plate metal being forced up around the perforations in cone-form as at 5 and ruptured in the punching process to provide a series of lances 6 around each perforation.
The blank 1 of FIGS. 1 and 2 is rolled up into trough form to provide a ferrule forming member 7 as seen in FIG. 3. The cone form groups of lances 6 are arranged at the base region of the trough.
To facilitate manufacture, the ferrule-forming member of FIG. 3 is formed in a strip comprising a plurality of ferruleforming members arranged end to end, adjacent members being connected together by short carrier strip portions. Thus the blank of FIGS. 1 and 2 is shown with carrier strip portions 8 and 9, which in manufacture are integrally formed with respective carrier strip portions 9 and 8 of adjacent blanks to define a strip of integrally connected blanks suitably stamped from a metal strip in a single operation. The are formed during or after the stamping operation with respective groups of perforations and the trough sides are subsequently rolled up whilst the ferrule-forming members are in strip form, the trough sides extending longitudinally of the strip of ferruleforming members.
The conductor of FIGS. 4 and 5 comprises a central electrically conductive core 10 surrounded by an electrically conductive braid shield 11 spaced from the core 10 by an annular layer 12 of readily deformable electrical insulating material, for example, polyethylene. The sheath I1 is surrounded by an external sheath l3 ofinsulating material which is stripped over a short terminal length to expose a short length of the braid shield 11. A ground wire 14 is secured to the braid 11 by a ferrule 15 formed from a troughlike ferrule-forming member as shown in FIG. 3. Ground wire 14 extends within the ferrule 15 along the base of the trough member in the perforated region of the ferrule. As seen in FIG. 5, the sides of the trough are closed together to define an annular ferrule tightly engaging the braid sheath II. Closure of the ferrule trough is effected in known manner by a crimping tool adapted to close the ferrule trough onto the braid 11 and exert a crimping force sufficient to cause indentation of the lances 6 into the braid shield. Closure of the ferrule sides causes the V-shaped projection 3 to cooperate with the V-recess 2 to define therebetween a narrow elongated V-shaped slot 16 through the ferrule length. The internal surface of the ferrule contacts the braid shield without substantial pressure being built up to cause extrusion of the insulating material 12.
Ground wire 14 is arranged in serpentine form within the ferrule 15 in order to improve pullout strength of the connection. To this end the perforations 4 are staggered longitudinally of the ferrule 15, and due to the cone-form 5 of each series of lances 6, engagement of the sides of the lances with ground wire 14 tends to displace it into a series of bights around respective perforations and thereby effect the serpentine form. The perforations may, for example, be arranged in groups of 5 having a central perforation within a square arrangement of four perforations.
If ground wire 14, which may be solid or stranded, lies directly below a ferrule perforation 4, then the lances 6 around the perforation will tend to be flattened under the influence of crimping pressure against the ground wire. The cone-form 5 and convergent nature of e the lances 6 at each perforation facilitates this flattening which avoids transmission of excess local crimping pressure through ground wire. 14 and consequent local thinning of the insulation I2 opposite to the ground wire.
The lances 6 act as standoff means serving to effect mechanical and electrical connection with the shield metal without requiring excessive crimping pressure to urge the ferrule against the braid shield against the spacing effect of the ground wire. 1
In the modified connection of FIG. 6 like reference numerals refer to similar parts of FIGS. 1 to 5. No ground wire is provided and the V-shaped projection 3 and recess 2 are omitted. One edge of the ferrule I5 is prolonged to provide a tab 20 formed as a ring tongue 21 for receiving a securing bolt. The ferrule 15 is rolled up at one end to define a P-shaped cross section circumscribing the braid shield 11 at one end and extending sidewardly substantially tangentially of the braid shield at the other end.
For applying ferrules according to the invention by an automatic crimping and severing machine and using a strip of ferrule-forming members arranged end to end as has been described, ground wire is suitably fed in the machine with the strip towards a crimping station. The ground wire is fed by a feed finger of the machine which also feeds the strip so that a portion of the ground wire lies within each ferrule-forming member at the crimping station. Each ferrule-forming member 15 must be connected with a length ofground wire 14 exceeding the length of the ferrule 15 by an amount sufficient for making a separate ground connection. To this end the feeding stroke of the finger must be greater in relation to the ground wire than it is with relation to the strip of ferrule-forming members. The feed finger is thus suitably cammed towards the end of its return stroke onto a platform beneath which the strip of ferrule-forming members 15 is fed. The working tip of the ed fewer supported by the platform out of feeding engagement with the strip during the initial part of its feeding stroke, Thus whilst the wire 14 is fed through the full forward stroke of the feed finger, the strip of ferrule-forming members is fed through only part of the stroke. By suitable adjustment of the platform position a proper length of ground wire may be fed to each ferrule-forming member.
1. An electrical connection comprising: coaxial cable means having an electrically conductive core, shield means and insu lation disposed therebetween; ferrule means crimped onto said shield means, said ferrule means having inwardly directed perforations defining shield-engaging means which key into said shield means without penetrating into said insulation; and conductor means connected to said ferrule means and extending therefrom for connection with another conductor means, said conductor means being a ground wire disposed between said shield means and said ferrule means and which is displaced in a series of bights around respective perforations to effect a serpentine form,
2. An electric An electrical connection according to claim fl wherein said shield-engaging means are cone shaped and in clude a series of lances at the innermost end of each of said inwardly directed perforations.
3. An electrical connection according to claim 1 wherein the crimped connection between said ferrule means and said shield means is of substantially even cross section .therealong.
4. An electrical connection according to claim 3 wherein mating edges of said ferrule means include V-shaped projection and recess means.
5. An electrical connection comprising a shielded insulated O conductor having an outer shield separated from a center electrical conductor by insulation, a ground wire, and a ferrule crimped around said shield with said wire therebetween, said ferrule being a thin member having spaced over its inner surface shallow hollow cones with jagged outer edges and which are easily flattened, said cones indenting said shield without cutting therethrough into said insulation, said ground wire lying in serpentine form in a series of bights around respective ones of said cones.
s. A method of making a ground connection onto shield means disposed over insulation means of a coaxial cable, said method comprising the steps of placing a ground wire onto a section of the shield means, arranging a connecter having staggered inwardly directed projections onto said section and over said ground wire, and crimping said connecter onto said section with said projections keying into said shield means without penetrating said insulation means thereunder thereby electrically securing said connecter onto said shield means and causing said ground wire to be displaced around respective perforations as a series of bights defining a serpentine configuration.
7. A method of forming an electrical connection to the outer braid of a shielded insulated conductor, said method comprising taking a ferrule formed into a trough and having assume a serpentine shape and displacing said wire into a series of bights around respective lances.