Electrical Terminal For A Braided Shield On A Coaxial Cable

Abstract

The present invention discloses an electrical terminal for grounding the braided shield on a coaxial cable. The terminal has beveled, inwardly projecting lances on each sidewall of the ferrule forming portion which separates the strands of and slides behind the braided shield so as to lace the shield between the sidewalls and lances to provide mechanical support and electrical contact.

Description

BACKGROUND OF THE INVENTION

In various applications and particularly in some radio frequency applications it is necessary to terminate the outer conductive braided shield of a coaxial cable to a ground. In these applications it is desirable to terminate the braided shield without interrupting the center conductor and dielectric surrounding it.

Some of the known prior art provides electrical connectors or terminals for connecting the braided shield to an electrical lead which is in turn attached to a ground. For example, U.S. Pat. Nos. 3,194,877 and 3,549,787 disclose terminals of this nature.

U.S. Pat. No. 3,435,126 teaches a metal band having a plurality of prongs which bit into the braided shield. The metal band is directly attached to a ground by means of a hose clamp which is threaded through slots in the ground.

Whereas the above cited patents and others in the art provide means for adequately grounding the braided shield, they either require a separate electrical lead, a number of components or detailed preparation of the cable to be grounded.

Accordingly it is an object of the present invention to provide a low cost, stamped and formed electrical terminal for grounding the braided shield on a coaxial cable quickly and simply and which provides good mechanical and electrical properties.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a perspective view of the terminal constructed in accordance to the present invention and a prepared coaxial cable to be terminated;

FIG. 1b is a transverse cross-sectional view of the terminal and cable of FIG. 1a;

FIG. 2a is a perspective view of the cable partially pressed into the terminal of FIG. 1a.

FIG. 2b is a transverse cross-sectional view of the terminal and cable taken along lines 2b--2b of FIG. 2a;

FIG. 3a is a perspective view of the completed termination of the cable into the terminal of FIG. 1a;

FIG. 3b is a transverse cross-sectional view taken along lines 3b--3b of FIG. 3a; and

FIG. 3c is an axial cross-sectional view taken along lines 3c--3c of FIG. 3a.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the accompanying drawings, the number 10 designates generally a length of a coaxial cable comprising from the center outwardly, a primary conductor 12, a conductor insulation or dielectric 14, an outer conductive braided shield 16 and lastly the outer insulation jacket 18. Braided shield 16 is commonly made of one or more layers each of which contain many strands of fine wire braided together. Cable 10 is prepared for termination to a terminal by stripping away a portion of the outer jacket 18 so as to expose shield 16. Where center conductor 12 is to be terminated also, a portion of shield 16 and dielectric 14 is removed.

Referring now specifically to FIGS. 1a and 1b, an electrical terminal 20 constructed in accordance with the present invention is shown. The terminal is made from electrically conductive sheet metal such as phosphor bronze or brass, and is blanked and formed by conventional metal-stamping and metal-forming techniques.

At the front end of terminal 20, an offset ring tongue 22 on connector portion 24 provides the means to attach electrical terminal 20 to a suitable ground or the like (not shown). As is well known to those skilled in the art, terminal 20 may be made with other forms of tongues (not shown) other than ring tongue 22. Connector portion 24 also includes an upstanding member 25 extending from one side thereof to provide structural strength to ring tongue 22.

Behind connector portion 24 and integral therewith is a generally U-shaped braided shield ferrule-forming portion 26.

A U-shaped insulation-support wire barrel 28 extends from and is integrally connected to ferrule-forming portion 26 by offset portion 27 which displaces wire barrel 28 downwardly relative to ferrule-forming portion 26 by a distance substantially equal to the thickness of insulating jacket 18.

Wire barrel 28 includes a base portion 30 and a pair of upstanding sidewalls 32--32 extending from opposite sides of base portion 30. The inside surfaces of base portion 30 and sidewalls 32--32 are generally smooth but may be ridged (not shown) or otherwise roughened to enhance the retention of cable 10 therein.

The U-shaped braided shield ferrule-forming portion 26 includes the bight or base portion 34 and a pair of upstanding sidewalls 36--36 extending upwardly from opposite sides of base portion 34. As FIG. 1b indicates, sidewalls 36 are initially formed so that they are spread outwardly; i.e., away from each other, a few degrees from the vertical. This spreading provides a larger opening into ferrule-forming portion 26 for cable 10.

A pair of lances 38--38 are stamped out of each of the two sidewalls 36 and are integral with base portion 34. Each lance 38 is formed to project inwardly and extend upwardly parallel to sidewalls 36 and is also swaged to provide a sharp inwardly-disposed tip 40 and an outwardly-disposed beveled portion 42. The height of lances 38 preferably is equal to about three-fourths the diameter of cable 10 without jacket 18.

The distance or spread between lances 38 on opposite sidewalls 36 is substantially equal to the diameter of dielectric 14 of cable 10.

Transverse openings 44 which result from the stamping and forming of lances 38 provide means for visual inspection of the assembled termination of FIGS. 3a, b, and c.

METHOD OF TERMINATING A COAXIAL CABLE HAVING A BRAIDED SHIELD ONTO THE PREFERRED EMBODIMENT

A coaxial cable 10, previously prepared in the manner described above, is aligned over terminal 20 so that the exposed braided shield 16 is directly over ferrule-forming portion 26. The axial length of exposed shield 16 substantially equals the axial length of ferrule-forming portion 26 and insulating jacket 18 terminates in the immediate vicinity of offset portion 27; i.e. adjacent to ferrule-forming portion 26. This alignment is illustrated in FIGS. 1a and 1b.

FIGS. 2a and 2b illustrate how lances 38 pierce braided shield 16 as cable 10 is being pressed into terminal 20. As tips 40 move in under braided shield 16, a portion thereof is being forced down the outside beveled portion 42. Such portion is hereinafter designated as the outboard portion 46 of braided shield 16.

Termination of coaxial cable 10 is completed when it has been pressed down completely into terminal 20 with sidewalls 32 being crimped around insulating jacket 18 and sidewalls 36 being crimped around braided shield 16 in the manner shown in FIGS. 3a and 3b. As the crimping dies used (not shown) are conventional and well known in the art and do not form part of the instant invention, further detail thereof is unnecessary.

As seen in FIGS. 3a, 3b and more particularly in FIG. 3c, outboard portions 46 are laced through and thereby trapped between lances 38 and sidewalls 36.

Lances 38 retain a residual force in an outwardly direction; i.e. toward transverse openings 44. Thus should sidewalls 36 relax away from the crimped position seen in FIGS. 3a and 3b, lances 38 will follow thereby maintaining electrical pressure contact between terminal 20 and braided shield 16.

Another novel feature in the present invention is that the lances 38 do not penetrate dielectric 14 nor jacket 18 and thus trap this material in the electrical connection. The termination is thus free of matter that is subject to creep or flow. The termination may be subject to stresses such as tension and temperature changes without destroying the mechanical or electrical termination.

Although the preferred embodiment of the present invention utilizes four lances 38, it is apparent that one lance 38 will also provide the same mechanical advantages but not to the degree as achieved using four or more.

It should be noted that terminal 20 may be used at any point along coaxial cable 10 and not necessarily adjacent the cable end. The amount of insulating jacket 18 that needs to be removed is only the axial length of braided shield ferrule-forming portion 26.

As is apparent to those skilled in the art, wire barrel 28 may be cut away from terminal 20 and not used.

As is also apparent to those skilled in the art, ring tongue 22 may have the form of a tab, spring contact, be the outer shell of a coaxial contact or any other convenient means of making a ground connection.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, as some modifications will be obvious to those skilled in the art.

Claims

What is claimed is:

1. A sheet metal electrical terminal for terminating the braided shield on a coaxial cable, comprising:

a. a generally U-shaped ferrule having a base portion and a pair of sidewalls connected to and extending upwardly from opposite sides of the base portion;

b. a pair of lances extending from each sidewall, said lances attached at one end to each sidewall with the other end extending upwardly from the base portion and inwardly toward the opposite sidewall, each lance being formed into a generally four sided pyramid, the free end being pointed, said lances adapted to pierce and slide in behind portions of the braided shield of a coaxial cable which may be pressed into the ferrule; and

c. a pair of openings on each sidewall in alignment with said lances so that as the lances slide in behind portions of the braided shield, such portions may project into the openings.

2. A stamped and formed sheet metal electrical terminal for grounding the braided shield on a coaxial cable, which comprises:

a. a U-shaped ferrule-forming portion having a base portion and a pair of upstanding sidewalls extending from opposite sides of said base portion, said sidewalls adapted to be crimped into encompassing engagement with said braided shield, said ferrule-forming portion further having two pair of adjacent, upwardly extending lances with each pair on either side of said base portion and positioned internally of said sidewalls, (with each lance in each pair beind adjacent to the other), said lances having a beveled outwardly-facing sides and sharp tips on the free end thereof, said lances adapted to pierce and slide inbehind said braided shield so that a portion of said shield becomes laced between said lances and said sidewalls;

b. connector means integrally attached to one end of said ferrule-forming portion, said connector means comprising a flat portion being coplanar with said base portion of said ferrule-forming portion and an upstanding member integral with said flat portion and adapted to structurally support said flat portion, said connector means adapted for being attached to a ground;

c. a U-shaped insulation-support wire barrel having a base portion and a pair of upstanding sidewalls extending from opposite sides of said base portion, said sidewalls adapted to be crimped into encompassing engagement with said coaxial cable; and

d. connecting means for connecting said wire barrel to another end of said ferrule-forming portion whereby said base portion of said wire barrel is displaced downwardly from said base portion of said ferrule-forming portion.