US 3296363 A
Description (OCR text may contain errors)
Jan. 3, 1967 R. c. LAUDIG ETAL 3,295,363
CRIMPED COAXIAL CABLE CONNECTION WITH KNURLED EXTENSION 2 SheetsSheei v 1 Filed May 28, 1964 s R m N E V N FRANK BENJ'AWN STARK RONALD CLAIR LAUDIG- (WM, y gfl-w Jan. 1967 R. c. LAUDlG ETAL 3,296,353
CRIMPED COAXIAL CABLE CONNECTION WITH KNURLED EXTENSION Filed May 28. 1964 2 Shee'ts-Sheet 2 I N VEN'TORS FRANK BENTAM\N. STARK Roumm CLAIR LAUDIG BY H...
United States Patent 3,2%,363 CRIMPED COAXIAL CABLE CONNECTIGN WITH KNURLED EXTENSION Ronald Clair Laudig, Camp Hill, and Frank Benjamin Stark, Wormleysburg, Pa, assignors to AMP Incorporated, Harrisburg, Pa.
Filed May 28, 1964, Ser. No. 370,793 2 Claims. (Cl. 174-89) This invention relates to an improved connector of the type adapted to be crimped to coaxial cable.
The widening use of cable having an outside metallic sheath or braid adapted to shield an inner center conductor from RFI has served to generate a number of problems and shortcomings with existing coaxial connectors. One of the problems is related to connector uses which cause the connector or the cable to become twisted to apply a torsional load to the connection therebetween and thereby cause the connector body to rotate relative to the cable, thus, breaking down the necessary metallic interface between the connector .and the cable conductors.
This type of problem frequently arises with test equipment wherein the connector is repeatedly twisted onto or out of a receptacle mounted on the chassis of the equipment. A further problem has been encoutered with cables having braided sheathing crimped between an inner connector sleeve and an outer ferrule, in cases wherein the surfaces of the members are smooth and wherein one of the surfaces includes small tranverse serrations. This further problem has contributed to connection failure by reason of the cables being pulled out of a connector due either to an inadequate interlocking surface or due to the cable braid being severed by the forces applied during crimping. All of the foregoing problems are compounded with cable of the type having a double layer of braid. It is a general object of the invention to overcome the foregoing shortcomings by providing a coaxial connector crimping sleeve of a configuration to prevent either tensional or torsional loads from separating the connector from attached cable.
It is a further object to provide a connector having a crimping sleeve with at least a portion thereof serrated to define surfaces which engage thesurfaces of a crimping ferrule formed thereagainst to lock a cable braid therebetween against either twisting or pull-out forces developed during connector use and to establish a stable inter face of low resistance between connector or cable.
It is another object to provide a connector crimp sleeve having serrations in the outer surface of a configuration to accommodate the standard lay of cable braid.
Yet, a further object is'to provide a coaxial connector with a crimping sleeve relieved to accommodate a wide range of cable braid diameters and configurations.
Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there are shown and described illustrative embodiments of the invention; it is to be understood, however, that these embodiments are not intended to be exhaustive nor limiting of the invention, but are given for purposes of illustration in order that others skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in "ice various forms, each as may be best suited to the conditions of a particular use.
The invention contemplates a coaxial connector construction which includes a sleeve extension having serrations or grooves against which the metal of the connector crimping ferrule is formed. In one embodiment the extension surface is knurled in crossing and spiraled grooves to define surfaces which lock the connector against both twisting and pull-out forces. In the alternative embodiment, the extension surface is serratedin interaxial and tranverse grooves which lock against such forces. In both embodiments, the outer conductor of attached coaxial cable is entrapped between the outer surface of the connector sleeve extension and the inner surface of the crimping ferrule and is thereby locked to the connector against either of the aforementioned failure modes. The forming of the metal of the connector ferrule takes place in both embodiments to an extent to develop working of the surfaces of the ferrule, extension and cable outer conductor to provide a stable interface therebetween.
In the drawings:
FIGURE 1a is a perspective view of a connector half of the invention in one embodiment;
FIGURE lb is a perspective view of joined connector halves crimped to coaxial cable;
FIGURE 2a is a longitudinal section of the connector of the invention in one embodiment with the ferrules thereof crimped to terminate attached cables;
FIGURE 2b is a cross-sectional view taken along lines 22 of FIGURE 2a;
FIGURE 3 is a perspective view of an alternative version of a connector half of the invention; and
FIGURES 4a and 4b are perspective views of types of coaxial cable braid served by the invention embodiments.
Referring first to FIGURE 4a, a coaxial cable 10 is shown to include a center conductor 12 surrounded by a dielectric sheath 14 and an outer conductor 16, in turn, surrounded by an insulating and protective sheath 18. The outer conductor 16 is of a standard type made of interwoven strands of conductive wire to form a braid which extends in crossing spirals along and about the dielectric sheath 14. In FIGURE 412, an alternative cable construction is shown wherein the braid 16' is of interwoven strands of conductive ribbons or foil.
In both constructions, the general purpose of 16 and 16 is to shield the center conductor 12 and the signals carried thereby from being modulated or otherwise af fected by stray RFI. In most uses, the outer conductor is earthed or connected'to chassis potential. In any event, when the cable is terminated, the outer conductor becomes the only practical and effective member for holding the cable to the connector to which the cable is attached. Thus, it is of considerable importance to obtain a good mechanical connection with the cable outer conductor. For proper circuit continuity, it is also important to maintain a good electrical connection between the cable, outer conductor and the outer conductive portions of the connector.
For the cable construction shown, it should be apparent that tensional or torsional cable stresses primarily through the braid and when applied to a connector of prior art construction operate, respectively, to tend to pull the cable off or cause the braid to rotate about the '3 connector crimping extension. The former, of course, will result in both mechanical and electrical failure of connection and the latter will, at least, break up the interface between the connector and the braid.
Viewing now FIGURES 1a-2, the solution offered by the present invention will now be detailed. In FIGURES 1a2, there is depicted a connector half 20 and a complementary half 20' each having at the rear end thereof a sleeve extension 22 internally bored at 24 to a diameter approximating the diameter of the cable sheath 14. The bore 24 extends through 22 into a central cavity of 20 wherein is housed a center contact and insulating support structure 30 or 30' in half 20. Extension 22 further includes at the outer end a beveled portion 26 adapted to assist the entry of the extension under the braid 16 during assembly. Disposed on the outer surface of 22 and shown along the length thereof are grooves 28 and 29 which spiral oppositely to form a knurled surface defining pyramidal projections. FIGURE 2a shows this in longitudinal section and FIGURE 2b shows the cross-sectional appearance resulting from 28 and 29 relative to the thickness of 22 and to the thickness of the strands of 16.
In use, the grooves 28 and 29 define surfaces which are oblique to both the longitudinal axis and to the transverse axis of the cable. Thus, the surfaces operate to resist both torsional and tensional loads developed in the cable and in the braided thereof. Fitted over extension 22 and extending back along the cable over the sheath 18 is ferrule 32 formed of malleable construction material. The length thereof extending out over the cable sheath 18 provides mechanical support to the cable to, in a sense, better isolate the initial area of contact from bending loads developed on the cable. The rear edge of 32 includes a folded in portion 34 which, when the ferrule is crimped inwardly, forms a partial seal through an annular compression of the sheath 18; preferably without deforming the braid 16 or sheath 14. The type of crimp preferred is known as an O crimp and is generally described in copending application, Serial No. 268,873, filed March 29, 1963, by F. B. Stark, now US. Patent No. 3,212,050, although it is contemplated that other types of crimps may be employed with the features of the invention.
The ferrule 32 is shown as a relatively thin member crimped inwardly to lock the strands of 16 within grooves 28.and 29. In practice, a ferrule thickness is used sufficient for the ferrule to be crimped inwardly enough to cause the parts of material of 22 to bite into the ferrule material and lock the ferrule to the extension. This is shown in FIGURES 2a and 2b. As the ferrule material is driven inwardly, it entraps and works against the strands of 16 to break up any oxidation products on the surfaces of the ferrule bore, the extension outer surfaces and the braid to provide clean metal for forming a proper interface therebetween. In some prior devices, these surfaces were slightly worked radially but not enough to provide large areas of metal having the surface contamination sufficiently fragmented to provide a good merger of metal. Also, with double braid, the upper portions of the projections formed by 28 and 29 penetrate the braid so as to lock both layers.
As can be apprehended from FIGURES 4a and FIG- URES 1a, 2a and 2b, the knurled surface formed by grooves 28 and 29 defines a spiral which complements the spiral of the braid 16. In practice, the strands of 16 are driven down into the grooves in a crossing and interlocking mesh so that tensional forces applied to the cable are resisted by definite portions of extension material. So too, with respect to torsional forces.
FIGURE 3 shows an alternative version of grooves which may be preferred with certain types of braid construction. In FIGURE 3, the grooves are shown as 40 and 42 applied to sleeve extension 22 in transverse and longitudinal series relative to the extension length. In
4 this embodiment, the same result obtains with respect to defining surfaces which lock the cable braid against both tensional and torsional loads. With braid which is comprised of closely-spaced spirals such as is shown in FIG- URE 4b, the surface shown in FIGURE 3 may be preferred.
With standard wire braid of a wire diameter approximately 5 thousandths of an inch, an actual embodiment of the invention employed a ferrule of hard-drawn annealed copper approximately 10 thousandths of an inch in thickness. The extension 22 was 25 thousandths of an inch in thickness overall and the grooves 28 and 29 were about 6 thousandths of an inch deep. The grooves were spiraled at an angle of approximately 30 relative to the longitudinal axis of the connector. A sample made accordingly resisted torsional stresses to an extent to break the attached cable Without disturbing the connection between cable and connector. In uses with fiat or foil braid, the ferrule would preferably be thicker out of a more malleable material so as to be worked well down into the grooves of the extension without cutting the foil. The projections which are pyramidal in FIGURES 1a-2 may also be of other configurations to better work within the interstices of the braid.
The invention while developed with braid problems in mind can be used with cable having a solid metal outer conductor, such as, solid copper or aluminum. In such use, the grooves would be made of a depth relative to the construction metal characteristics including thickness. The embodiment of FIGURE 3 is preferred for such use.
As a final point, the sleeve exterior has been shown with the grooves disposed along the length thereof. It is contemplated that the grooved portion may be made to extend for less than the entire extension length although it is preferred that such surface be at least of a length approximately the diameter of the cable.
Changes in construction will occur to those skilled inthe art and various apparently difierent modifications and embodiments may be made without departing from the scope of the invention. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only. The actual scope of the invention is intended to be defined in the following claims when viewed in their proper perspective against the prior art.
What is claimed is:
1. In a coaxial connector assembly including a connector and a coaxial cable of the type having an outer conductor comprised of spirally woven and braided metallic strands surrounding an inner conductor and spaced therefrom by a dielectric sheath, a connector body including a metallic tubular member having a dielectric insert therein carrying a center contact member, said body including a rear conductive sleeve extension and a malleable ferrule member adapted to be fitted over said sleeve extension, the said cable being attached to said connect-or with the inner conductor thereof fitted within and terminated to said center contact member, the said extension having an outer diameter slightly larger than the inner diameter of said outer conductor and including an outer surface defined by a series of first and second grooves disposed thereon in a crossing relationship to define surfaces oblique to each other and a series of projecting points, said grooves being of a depth approxi mating the thickness of the strands of the said outer conductor, the said ferrule being of a thickness and inner diameter slightly larger than the outer diameter of said extension with the outer conductor of said cable fitted thereover and crimped inwardly along the length of said extension to a point wherein the projecting points defined by said grooves are engaged by and in contact with the inner surfaces of said ferrule with the strands of the outer conductor of said cable forced down within said grooves and deformed therein whereby said connector is 5 6 locked mechanically and electrically to said cable to resist References Cited by the Examiner tcgrbsliggllaclnaggdtzgjrogggrforces tending to separate said UNITED STATES PATENTS 2. The assembly of claim 1 wherein said first and sec- 3184'535 5/1965 Worthington 174 '94 XR and grooves each have a spiral configuration in relative 5 3,206,540 9/1965 Cohen 17489 opposite directions and crossing along the length of said 3221290 11/1965 Stark et a1 174' 89 XR extension arranged in a pattern generally following the woven pattern of the strands of the braiding of said outer LEWIS MYERS Puma Exammer' conductor, D. L. CLAY, Assistant Examiner.