US 3212050 A
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Description (OCR text may contain errors)
Oct. 12, 1965 F. B. STARK COAXIAL CONNECTOR 5 Sheets-Sheet 1 Filed March 29, 1965 INVENTOR FRANK B, STARK Oct 12, 1965 F. B. STARK 3,212,050
GOAXIAL CONNECTOR Filed March 29, 1963 3 Sheets-Sheet 2 INVENTOR.
FRANK B. STARK BY km, W W
Oct. 12, 1965 F. B. STARK 3,2
COAXIAL CONNECTOR Filed March 29, 1963 3 Sheets-Sheet 5 INVENTOR FRANK B 5TARK BY United States Patent 3,212,050 COAXIAL CONNECTOR Frank B. Stark, Harrisburg, Pa., assignor to AMP Incorporated, Harrisburg, Pa. Filed Mar. 29, 1963, Ser. No. 268,873 4 Claims-(Cl. 339-177) This invention relates to improvements in connectors of the type utilized to interconnect coaxial cable and particularly to connectors used to interconnect high frequency signal paths.
The most basic requirement of coaxial connectors capable of handling high frequency signals is that of low loss and lack of signal degradation. This requirement is measured by the voltage standing wave ratio (VSWR) present in a transmission path including the connector under test. Of the various difficulties experienced with coaxial connectors having a low VSWR over an extended frequency range, one of the more troublesome has been with the center conductor connection.
The typical prior art approach to center conductor connections has been to utilize a centrally disposed tubular pin member soldered to the cable center conductor. Unfortunately, the usual shortcomings attending the use of solder are magnified in high frequency applications wherein signal reaction to impedance mismatch and to discontinuities can cause substantial loss. For example, if the net composition of solder employed is significantly different from that used during design of the connector, signal alteration may be expected. If too much solder is used the parts may not fit without trimming olf the solder, which operation will affect the electrical characteristics of the connector. Similarly, if too much heat is used during the soldering process, the various dielectric materials of the connector will be damaged, directly and significantly affecting both the mechanical connection and VSWR achieved by the connector.
Even within the range of neither of too much not too little, the slight differences attributable to different personnel assemblying connectors will cause variations resulting in assembly tolerances analogous to manufacturing tolerances, but more difiicult to control. In a word, the use of the soldered center conductor connection in high frequency connectors leaves the quality of even the best designed connector up to the soldering skill of the person assemblying the connector.
Accordingly, it is a primary object of this invention to provide an all-crimped coaxial connector for use with relatively high frequency signals.
It is another object to provide an all-crimped coaxial connector having a low VSWR.
It is yet another object to provide an improved coaxial connector featuring a crimped center conductor connection which minimizes impedance mismatch and discontinuites within a connector. It is a further object to provide a broad band coaxial connector capable of being assembled in a rapid and reliable manner with minimum variation in the electrical and mechanical characteristics of the average connector.
It is a particular object to provide a coaxial connector having a crimped center conductor connection which does not require compensation. V
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 3,212,050 Patented Oct. 12, 1965 the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the condition of a particular use.
The foregoing objects are attained in .hte present invention by the provision of a connector construction adapted to receive and position the separate conductive and insulating parts of a coaxial cable and be connected thereto by two cn'mps, which do not distort the dimensional integrity of the connector components or cable. The connector features a backing shell over which a ferrule is crimped to electrically and mechanically connect with the cable and the outer conductor thereof. The connector also features a central pin member having a crimped segment of a material thickness prior to crimping such that the outer surface of the pin will be constant and smooth following the crimping operation to provide a low VSWR. As a result of these features, special compensation at the point of crimp and the attendant complexities of construction and assembly are avoided. Moreover, the connection of the invention may be used with crimping tools capable of providing an identical crimp, irrespective of the differences in skills of personnel. 7
By following the procedure hereafter outlined, coaxial connectors may be made to have a VSWR at least equal to that of the best soldered connector on a unit basis. Because of the constancy inherent in the connection of the invention, a superior VSWR may be achieved on an average production basis. These advantages are in addition to substantial savings in cost per unit connection.
In the drawings:
FIGURE 1 is a perspective of the coaxial connector assembly of the invention including interconnecting connector halves joining the ends of coaxial cable;
FIGURE 2 is a longitudinal section taken along lines 22 of the assembly shown in FIGURE 1;
FIGURE 3 is a longitudinal view, partially sectioned, of half of the connector of the invention mounted on the coaxial cable prior to the crimping operation;
FIGURE 4 is an enlarged longitudinal sectional view of a portion of the central pin member crimp segment shown in FIGURE 3;
FIGURE 5 is a cross-sectional view taken along lines 55 of FIGURE 3;
FIGURES 6 and 7 depict cross-sectional views of the central pin member of the invention before and after crimp, respectively, related to sections along lines 6-6 and 77, in FIGURE 2, in conjunction with partial views of the die faces of tooling employed;
FIGURES 8 and 9, show longitudinal and cross-secsional views respectively, of a further embodiment of a crimp which may be used with the central pin member of the connector of the invention;
FIGURES 10 and 11, show longitudinal and crosssectional views of a further embodiment of the central pin member of the assembly of the invention; and
FIGURES l2 and 13 show longitudinal and cross-sectional views of the members shown in FIGURES l0 and 11; following the crimping operation.
Turning now to a description of the invention and referring to FIGURES 1 and 2, assembly 10 is a coaxial connector interconnecting coaxial cables 12 and 20 of the type utilized to carry signals having a possible frequency range of 0l0,000 megacycles. Cables 12 and 20 include, as shown in FIGURE 2, a central conductor 14 surrounded by a dielectric core 16, having an outer conductor 18 thereo-ver and a protective sheath 19 of flexible insulating material as an outside cover. Connectors of this general type are well known and widely used to provide a connect-disconnect function between the signal paths of electrical electronic equipment such as, for example, between the various components of radio, radar devices and the like. Assembly consists of halves 22 and 32 each crimped to the inner and outer conductors 14 and 18 of cables 12 and 20, and adapted to mate to perform electrical contact between cable paths by frictionally engaged complementary contact surfaces and mechanical contact by the well known bayonet engagement of the halves. As will be apparent from FIGURE 2, halves 22 and 32 are substantially identical, with respect to the structure thereof performing the crimping function, but modified in the forward portions thereof to provide complementing male and female parts. Briefly considered, connector half 22 includes a first conductive shell portion 24, threaded as at 26 to receive a forward shell portion 28, having at least two projections 30 on its forward outer surface adapted to engage the cam surfaces of slots 33, in the forward outer shell of half 32. This feature, well understood by those skilled in the art, permits half 22 to be inserted within half 32 and locked therein by relative rotation of the halves to displace projection 30 along slots 33, against the force of spring members provided in 32, to a position serving to lock the halves together. The inner surface of 28 defines a contact surface as at 29, with spring members extending from half 32. Half 22 further includes a forward dielectric insert 25 having a portion 27 adapted to fit within the complementary dielectric insert of half 32. The central conductive pin member 31, of half 22 includes, at its forward end, a split female contact spring member adapted to receive a complementary male portion of the pin member of half 32. Otherwise, half 22 is identical to half 32 to form therewith inner and outer signal paths between cables 12 and 20.
Connector half 32 includes a first conductive shell portion 34, having a forward portion threaded as at 36, to engage a forward shell portion 80. Integral with shell 34, is an extended portion 38 of a thickness adapted to serve as a support for a backing ferrule 45 crimped thereover. Portion 38 includes an inner bore 44, of constant diameter aligned with and inter-connected to a bore 48 within shell 34 by a tapered transitional bore 46. The outer surface of 38 includes a series of serrations or grooves 40 adapted to provide a gripping surface for holding the cable braid and the cable under the crimped face of ferrule 45. The outer end surface of 38 is tapered to facilitate positioning the cable braid over shell extension 38 during assembly. Fitted within the cavity formed of bores 44, 46 and 48, is a dielectric insert 50, which is tightly wedged and secured within the bores. Insert 50 includes a sleeve extension 52 extending the length of bore 44, and held against relative movement by a small projection or rim 43, at the end of 38. Rim 43 is preferably of the approximate diameter of the dielectric of the coaxial cable to be utilized with the connector assembly. Entrapped and held within insert 50, is a central pin member 56 coaxial with the shell 34 and the bores thereof. Pin member 56 is secured against relative axial movement by small annular projection 57, symmetrically disposed about the periphery of the pin end.
Central pin member 56 includes a bore 58 extending approximately half its length and a forward portion 60 of constant outer diameter with an end contact portion 62 of slightly less diameter adapted tofit within and mate with central contact pin 31 of half 22.
A forward conductive shell 80, is interconnected to shell 34 by internal its threading mating with external threading 36 thereof. Shell 80 includes a radially extending flange 84 at one end opposite to the threaded end defining a bearing surface for annular spring members 85, which are fitted within a recessed portion 83 and held by a locking ring 87, fitted around the same recessed diameter. Ring 87 further interlocks shell 80 with sleeve 88 adapted to fit over the forward end of shell 28 of connector half 22 and through slotted portions 33 intermate with the projection 30 thereof. Relative rotation of halves 22 and 32 serve to engage projections 30 and slots 33 to place spring members under compression and hold projections 30 within a relieved locking recess at the end of slot 33.
Fitted within an internal bore 86 of 80, is a dielectric insert 92 having an internal bore 94, of a diameter sufficient to receive the forward end 60 of pin 56 in a relatively close fit. Dielectric insert 92 serves to support pin 56 against relative movement and through its engagement with insert 27 the coaxial alignment of pin 31 with pin 56.
Surrounding the forward end of 92 is a conductive spring member 90 split to define resilient fingers 91 having raised portions 93 at the ends thereof to engage in frictional fit, the surfaces 29 of half 22. Spring member 90 is secured to 80 by means of an interconnection at 95 as shown in FIGURE 2.
The pairs of shells 25-28 and 34-80 are interconnectedas shown with annular dielectric spacers such as 51, of resilient material adapted to serve to accommodate cumulative axial tolerance deviations and seal the inner contact surfaces against environment. The thickness of the spacers should be such as to provide a radial and axial compression of the spacer material against the end faces within the assembly.
As indicated in FIGURE 2, it is preferred to maintain the diameters of shell bores and central pin members constant with respect to the lengths between transition bores in shells 24 and 32. Additionally, the dielectric materials employed should be selected to have dielectric constants which are similar each to the other and of values to provide an impedance per unit length of shell and pin compensating for any mismatch not compensated for by the spacing between the outer and inner diameters of pins and shell lengths, respectively.
It should be apparent from the foregoing description that assembly 10 provides from a mechanical standpoint, a stable coaxial interconnection between the signal paths of coaxial cables. It should be further apparent that assembly 10 includes features permitting the engagement and disengagement of connector halves repeatedly with substantially the same contact areas provided for the center and outer conductor paths forming the coaxial connection. The structural features of the assembly 10 minimize the possibility that the connector components will float or move relative to each Other due to temperature, vibration, or axial strains imposed upon the cable.
Turning now to a detailed description of the invention, the electrical connections provided in each connector half by crimps C and C operates to both mechanically and electrically connect the center and outer conductors, respectively of the coaxial cable to connector half 32. The crimp C applied along ferrule 45, operates as above described to mechanically connect cable 12 and electrically and mechanically connect the cable braid 18 to the outer metallic shell portions of connector half 32. Crimp C operates to mechanically and electrically connect the cable center conductor 14 to the central pin member 56 of connector half 32, in a manner to be hereinafter described. The crimps C and C are performed simultaneously by die face affixed to, and driven by, a common die actuating head manually or otherwise driven by common drive means, to complete both crimps in a single stroke of closure.
Referring now to FIGURE 3, there is shown a portion of connector half 32 removed and prepared by proper placement of cable parts for the crimping operation. As apparent, the ferrule 45 is of an inner diameter slightly larger than the outer diameter of the cable 12 to provide a space wherein the cable outer conductor or braid 18 may be readily inserted around shell 38. During the crimping operation, ferrule 45 is driven from the configuration shown in FIGURE 3, to the configuration shown in FIGURE 2, the forward half serving to lock braid 18 against shell 38, with portions thereof forced into serrations 40 around the periphery thereof. The rearward portion of ferrule 45 is forced into a configuration gripping the outer insulating sheath 19 of cable 12. It is preferred that the dimensions of shell 38 be such as to permit ferrule 45 to be driven to lightly compress sheath 19 without deforming the inner dielectric core 16 of the cable to altar the radial distance between the outer surface of conductor 14, and the inner surface of braid 18. The shell extension 38 is sufficiently strong as to prevent crimping forces from compressing insulating core 16 inwardly in the section of cable within the bore 44. It is preferred that crimp C be an O crimp similar in configuration to the crimp shown in cross-section in FIG- URE 5.
With respect to crimp C FIGURES 3-7 indicate a preferred construction for the segment of pin 56 utilized as a crimp zone. As FIGURES 3, 4 and 5 show, the precrimped confiuration of this segment is such as to provide an integral humped portion of metal material extending along the segment length. The humped portion is comprised of a segment 63 of a constant radius R with respect to the center conductor center-line and end spaced walls 64. During the crimping operation, the humped portion is driven inwardly from radius dimensions R to R with the surface of pin 56, as indicated in FIGURES 6 and 7. At the same time the inner surface of the humped portion is transposed to form an inwardly projecting surface of radius R is indicated by the shaded area in FIG- URE 4 and as shown in FIGURE 2 at the crimp denominated C The resulting configuration of pin 56 provides a spacing D along crimp C equal to the spacing D along the remaining portions of pin 56 with respect to the outer conductive shell members of the connector.
During the crimping operation a pair of dies, such as 110 and 114, are applied to the humpback portion in the manner indicated in FIGURES 6 and 7. The inner face 112 of die 110 should be of a substantially constant radius and as above as possible to a similar constant radius in the die face of die 114. Crimp C should provide a crimped area as close to being cylindrical as is possible. For this reason the slight offset indicated as 111, on each side of die face 112, is preferably maintained as small as is possible without operating to cause excessive die breakage. Die 110 is driven in the direction shown to close on pin 56, along the entire length of the humpback portion including segment 63 and both walls 64, and for a portion extending over the ends thereof such that the die faces bottom or close on the pin surface. As shown in FIGURE 7, closure should be completed to a point to fully compress the pin metal material and form center conductor 14, so that no free space is left between strands. This, of course, is determined by the pre-crimped dimension R in conjunction with the average diameter of conductor. If a solid, rather than a stranded conductor is used, the same procedure is followed with respect to die closure. This operation will serve so tightly grip the center conductor 14 around its circumference along a segment identical in length and configuration to the humpback portion. By completely compressing the material forming the humpback portion inwardly to deform the center conductor 14, the opportunity for the conductor becoming displaced within pin 56 and ensuing connection failure is minimized. The abutment represented by the transportation of walls 64 to 64 operates to bite into the conductor and hold against axial loads.
A controlling factor in the above operation is that the outer surface of the humpback portion, including the segment 63 and walls 64, should be left as close as possible identical in configuration and radius to the outer surface of the remaining portions of pin 56. In other words, the crimping stroke should drive the humpback portion from R to R along its length. As a practical matter this may be accomplished by calculating the difference between the volume of the segment of the central bore 58 of pin 56,
prior to crimp and the volume of such segment with the central conductor fully compressed, shown in FIGURE 7, and providing additional metal material in the form shown in FIGURE 5, equal to such difference. The stroke of die faces 110 and 114 may then be made such as to leave the outer surface of metal material throughout thehumpback portion disposed along radius R with conductor 14 connected to pin 58. The length of the humpback portion should be suflicient to preclude the inner bulge shown as 66, in FIGURE 4, from being sheared by axial loads placed upon the central conductor 14 and, more importantly, to provide a sufficient area of interface contact with the central conductor for good electrical connection.
The above features have been found to significantly contribute to the efliciency of high frequency electrical connectors by avoiding abrupt changes in conductor diameters and incident discontinuity capacitancies.
For general use the pin construction and crimp shown in FIGURE 3 is preferred. In certain instances design cost or other requirements may dictate alternative equivalents. For example, specifications may call for center connector pin members made of metals other than the standard beryllium copper or brass utilized and the characteristics of the central conductor may be other than those of the silverplated copper conductor utilized in standard cables. FIGURES 8 and 9 depict a central pin member 56' identical to pin 56 above described, but driven at C by a hexagonal crimp from the radius R to surfaces or radii greater and less than R the radius of pin 56'. The hexagonal crimp is only an approximation of the circular or O crimp shown and described with respect to FIGURES 6 and 7, but is, in certain instances, more easily accomplished and in any event, a
considerable improvement with respect to electrical characteristics over a deformed crimp section having a smaller cross-sectional area than the cross-sectional area of pin 56'. In this embodiment the post-crimped surface throughout the crimp zone is, as indicated in FIGURE 9, made such that the center part of each flat is of a slightly less radius than the radius R of the pin member and the radius of corner portions adjoining flats are slightly greater than the radius R of pin 56'. This results in a cross-sectional area through the crimp zone, which is substantially the same as the cross-sectional area through pin 56' and an approach to the smooth surface achieved in the embodiment of FIGURES 6 and 7. In the same manner, an octagonal crimp may be utilized, it being kept in mind that the particular crimp used is to be such that each portion of a different radius is balanced by a complementary portion and that the crimped configuration is symmetrical. The inner surface at C is driven to radii R to totally compress the conductor 14'.
FIGURES 1013, show yet a further embodiment of the invention wherein there is provided a pin crimp segment including humpback portions of segments 163- and 164 of noncontinuous longitudinal radius disposed on either side of a central pin member 158, having the use and function of pin 56 heretofore described. The configuration following crimp is shown in FIGURES l2 and 13, wherein the additional material represented by each hump is driven inwardly as at 166 to provide an interconnection with the central conductor 14. As in the embodiment of FIGURES 6 and 7, the volume of material represented by the humpcd portions should be of a thickness such as to completely compress center conductor 14 in the manner and provide an outer surface configuration identical to the outer surface of the remaining portions of pin 160.
While the present invention has been shown and described, with respect to a single type of coaxial connector, the invention is adaptable to any high frequency coaxial connector wherein it is possible to crimp rather than solder the central conductor within a central conductive pin member. Successful applications of the invention have been made on crimped versions of BNC, TNC, TPS and N type connectors. For the purpose of assisting one to practice thepresent invention, but without any intention to restrict the scope of the present invention, the following dimensions are given, based upon an actual unit constructed in accordance with the teachings of the invention exemplified in FIGURES 2-7 and found to have superior electrical and mechanical characteristics.
Inches Central pin radius, R 0.033 Central pin radius, R 0.039 Segment length, 64 0.080
Changes in construction will occur to those skilled in the art and various apparently different 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.
1. An electrical conector of the type utilized to interconnect radio frequency coaxial signal paths defined by cable including a central conductor surrounded by a dielectric core and an outer conductor, comprising, in combination, an outer shell of conductive material, a shell extension adapted to be crimped to the outer conductor of the coaxial cable by a ferrule crimped inwardly over said shell extension, the said shell including a central bore having a portion of constant diameter and having secured therein a dielectric core, a conductive pin member co-. axially secured in said core in one end thereof and extending axially through said core along said portion of constant diameter, the central pin member having a portion centrally relieved to accommodate the center conductor of the coaxial cable with a segment of said portion being of an increased wall thickness to define a humped portion integral therewith, said segment of said pin member being adapted to be crimped inwardly to form a mechanical and electrical connection with the center conductor with the surface configuration of said pin member at said crimp segment being substantially similar to the surface con figuration of segments of said pin on either side of said crimp segment whereby the spacing between the pin surfaces and the inner surface of said shell in said portion is constant along said portion.
2. An improved connector of the type utilized in coaxial connector asemblies to interconnect with the central conductor of a coaxial cable, including a conductive shell having a dielectric core, a pin member coaxially disposed in said core having a tubular end portion adapted to receive the cable central conductor and a crimp segment adapted to receive a crimp, driving pin wall material in against the central conductor to electrically and mechanically connect the pin with the conductor, the crimp segment having an integral humped portion of symmetrical cross-sectional surface configuration with portions of a sufficient thickness to permit crimping of said pin segment to the general surface diameter of said pin apart from said segment. l
3. The connector of claim 2, wherein the crimp segment has a post-crimp circular cross-section.
4. The connector of claim 2, wherein the crimp segment has a post-crimp non-circular cross-section.
References Cited by the Examiner UNITED STATES PATENTS 650,860 6/00 MCTighe 339-275 X 2,540,012 1/51 Salati 339177 X 2,672,596 3/54 Grypma 339-276 2,798,113 7/57 Koller et al. 339177 X 2,906,017 9/59 'Badeau 339276 X 2,958,929 11/60 Vineberg et al 339-276 X 3,112,977 12/63 Long et al 339177 JOSEPH D. SEERS, Primary Examiner.
W. DONALD MILLER, Examiner.