US3206540A - Coaxial cable connection - Google Patents

Description

Sept. 14, 1965 J, COHEN COAXIAL CABLE CONNECTION Filed May 27, 1963 INVENTOR. ere/n e ("o/9e)? BY for the clamp nut.

United States Patent 3,206,540 COAXIAL CABLE CONNECTION Jerome Cohen, 1341 E. 84th St., Brooklyn, N.Y. Filed May 27, 1963, Ser. No. 283,458 1 Claim. (Cl. 174--89) The present invention relates generally to coaxial connectors and particularly to a means of securing a connector onto a coaxial cable and to means of removably mating the connector onto a complementary connector.

Coaxial connectors are used to interconnect two ends of coaxial cable. Coaxial cable usually consists of a center conductor, an outer conductor, circumferentially disposed around the center conductor, a cylindrical dielectric occupying the space between the center and the outer conductors, and an outer cylindrical jacket over the outer conductor for its protection. The outer conductor, although in a few specific cases, may be made out of a solid metallic tube, is usually woven out of fine metallic threads in the form of a braid.

Heretofore, it has been the practice to separately strip the outer conductor, or braid, from the outer jacket of a coaxial cable before assembly with the connector. In addition the braid had to be cut at a different length than the jacket and a bare portion of the braid, without the jacket, was clamped between two metallic surfaces in the connector. This method of clamping the braid presented disadvantages since the fine wires comprising the braid could be damaged by being placed between the two metallic surfaces and rotated with respect to each other for tightening. Moreover, prior to the present invention, a tightening clamp nut which had an external threaded end was used to be inserted within a connector main body having an internally threaded end portion. This, of necessity, required a longer connector length to provide room By having a clamp nut over the connector body, the interior space may be used by the internal elements of the connector.

As a result of the recent trends in the electronic art, the need for an efiicient miniature coaxial radio frequency connector has increased in the past few years. Generally,

due to the increased use of transistors and other semiconductor devices in computers and general informa tion processing equipment, the power level of the electronic signals has been shifted from a high power level to a relatively low signal power level. Therefore, manmade noise interference, which has remained in the same average level or in some cases has increased, has become 'a more serious problem than it used to be. Consequently,

electronic devices require more shielding to presesrve opti rnum signal-to-noise ratios. Along with the development of a wider bandwidth semiconductors and the need for faster computations, higher frequencies are now involved in signal processing circuitry than were ever before attainable. Thus, While only a few years ago the timing clock-pulses in computers could be counted in the audio range, most computers today are synchronized by clocks at a much higher rate than heretofore obtained.

The digital data therefore, requires hundreds of megacycles of bandwidth for proper processing. Thus, the use of coaxial cable now becomes more necessary because higher frequency-carrying unshielded conductors radiate and therefore would lose signal power at a higher rate. Also, since the capacitive impedance to ground is lowered at high frequencies, a substantial part of the signal could be bypassed to the ground.

In addition, when coaxial cables are employed to connect one integral part of an electrical equipment with another, a connector which does not contribute a severe discontinuity in the coaxial line impedance is required to preclude the possibility of signal reflections in the form of ghosts.

Otherwise, ghosts may contribute to further loss of signal, noise and error. The trend for modular design continues due to the complexity of the new computers and data processing equipment, and thus the trend persists for building independent functional units which are interconnected during the systems assembly.

Miniaturization and reliability are other trends which have been emphasized in recent years because of the increase of aeronautical and space electronics. These trends, combined with the complexity of a large number of interconnected points, together with the demand for high reliability make the use of miniature connectors mandatory.

It is an object of the invention to provide an improved radio frequency coaxial connector having means for wedging, firmly, compressing and resiliently locking together the outer conductor and the outer jacket of a coaxial cable at one end portion of the connector.

A further object of this invention, is to provide a miniature coaxial connector which can be attached to a coaxial cable that is used for radio frequency systems, where the cable is firmly secured and locked by the connector with maximum strength and minimum electrical contact resistance having a minimum number of assembly parts, that can be manufactured and assembled at a lower cost than herebefore provided.

Still a further object of this invention is to provide a simple radio frequency minataure coaxial connector having a minimum number of parts, and is so constructed that it may be easily and completely assembled and disassembled onto a coaxial cable.

Other objects and features of the invention will appear as the description of the particular physical embodiment selected to illustrate the invention progresses. In the accompanying drawings, which form a part of this specification, like characters of reference have been applied to corresponding parts throughout the severalviews which make up the drawings.

FIGURE 1 is an exploded view of a preferred embodiment of the invention; and

FIGURE 2 is a sectional view of the same embodiment of the invention with the parts fully assembled.

To illustrate the invention and without intending to limit it to this specific apparatus, one female type of radio frequency miniature coaxial connector 10 is shown in association with a male type radio frequency miniature coaxial connector 11. A typical transmission line has a coaxial cable 12 attached tothe female type connector 10, and a coaxial cable attached to the male connector 11.

As shown in the accompanied drawing the female connector 10 comprises a frame assembly 13 having a clamp nut 14 at one end of a connector body 15, and a shield or guard 16 secured such as by a press fit at 17 to the other end of the connector body 15. In addition the female connector 10 comprises female internal assembly 18 having a ferrule 19, an inner insulator 20 and a female contact 21. The female contact 21 is removably secured to an outer insulator 22 which in turn is secured to the inside surface of the connector body 15. It should be noted that both the connector body 15 and the contact 21, have segmented circular elements or spring fingers 23 and 24 respectively, for receiving and holding an associated male jack and contact of the male connector 11, hereinafter specifically described. A ring spring 25 removably secured to the ends of the fingers 23 contributes to a firmer grip and better electrical contact of the male and female connectors. In addition, as shown, the shield 16 extends further endwardly than fingers 23 and radially inwardly thereof to guide and align the male connector 11 during the initial plugging operation before it hits the fingers 23. In addition the shield protects the fingers against damage due to external abusive contact with foreign objects and also it protects the fingers against bending moments applied to the connector through the coaxial cable.

The male connector comprises a frame assembly 26 having a clamp nut 27 designed for attachment to a connector body 28, having a jack portion 29. The jack portion 29 is provided with a semi-circular concave indentation 30 extending around its outer periphery to mate with a convex semi-circular protrusion 31 extending around the circumference of the inner surface at the end of the female fingers 23.

The male connector also comprises a male internal assembly 32 having a ferrule 19 as shown in FIGURE 1, as in the female connector, an inner insulator 33 and a male contact 34. The male contact 34 is removably secured to an outer insulator 35 which in turn is secured to the inside surface of the male connector body 28. It should be noted that when the male connector 11 is plugged into the female connector the male contact 34 is inserted within the fingers 24 of the female contact 21 and the jack 29 is guided by the shield 16 and is inserted within the fingers 23 of the female connector body 15.

Another main feature of this invention is the means of securing the coaxial cable 12 to both the male and female connectors to provide therewith an assembled transmission line. To better understand the invention a typical cable assembly procedure would be described. First, it should be noted that one of the primary purposes of this invention is to have a connector that can be easily and completely assembled and locked with a coaxial cable to provide an electrically and mechanically optimum transmission line. This purpose is accomplished by having a tapered knurled conical external surface 36 as part of the ferrule 19, and a conical internal surface 37 as part of the clamp nut 14, which has a sharper angle with respect to the connector axis than the knurled conical surface of the ferrule. Therefore when the clamp nut 14 is screwed onto the connector body the cable 12 will be wedged and locked between the surfaces 36 and 37.

The coaxial cable 12 is secured to the connector by first threading the clamp nut 14 onto the cable around the jacket 40. The jacket 40 and an outer conductor or braid 41 are cut the same length from the end of the cable. The cable is then trimmed oil so that an inner or center conductor 42 extends past an inner cable insulation 43. The jacket 40 is then slit at two places approximately 180 degrees apart for a short length and then ferrule end of the female internal assembly 18 having the contact 24 and insulator attached thereto is inserted within the slit jacket between the braid 41 and the inner cable insulation 43, as best shown in FIGURE 2, making certain that the center cable conductor 42 enters the hole in the contact 21. The jacket still secured to the braid 41 is clamped and locked between the two inclined or tapered surfaces 36 and 37 of the ferrule 19 and clamp nut 14, respectively. The inside surface 36 of the ferrule being knurled assists in holding the jacket and the braid combination between the two inclined surfaces. As hereinbefore described, it should be noted that as the clamp nut 14 is screwed onto a threaded portion 44 of the connector body 15, the ferrule butts against a retaining lip 45 formed in the internal cylindrical surface of the connector body 15. The space between the said surfaces 36 and 37 therefore gradually becomes smaller as the clamp nut 14 is screwed onto the connector body, 15. The combination of the resilient jacket, the knurl surface and the gradual decrease of the space between the surfaces provides for a very strong mechanical wedging grip, which secures and locks the cable into the connector. It should also be noted therefore that the method of utilizing the jacket as a gasket for compression and sealing eliminates the need for a separate gasket, heretofore employed in some connectors.

In addition, the inclined surfaces moving towards each other, as the clamp nut is screwed onto the body po-rtion of the connector, compress the jacket with the braid onto the knurled surface of the ferrule to provide thereby an effective optimum electrical and mechanical connection. Moreover, as hereinbefore described, this connector provides that both the outer conductor and the jacket do not have to be separately stripped and cut of different lengths prior to their assembly to the connector. As it can be understood, this feature allows a more economical product due to the simplification of the connector by use of fewer parts providing for a shorter time for assembly and lower labor cost.

The knurled surface of the ferrule, besides contributing towards a firmer grip, also provides for a better electrical contact and subsequent a lesser electrical contact resistance with the outer conductor of the coaxial cable. Finally, this invention provides for a pressure exerted on the inside surface of the outer conductor outwardly and a pressure exerted on the surface of the outer jacket inwardly thereby no pressure causing deformation of the dielectric is exerted on the cable dielectric itself. This arrangement therefore prevents possible severe deterioration of the transmission line characteristics at the connection of the cable with the connector.

As shown in the drawing another feature of the invention is the use of a clamping nut having internal threads which screw on over the main body of the connector. This allows the freedom of a shorter connector. If the invention is applied in the design of a connector of a standard length, and the clamp nut screwed externally of the main body of the connector, it will allow a longer internal volume for the inside parts of the connector. This provides therefore the advantage of making parts held more firmly and in a better alignment, for the same connector length. Conversely, if minimum required space is allowed for the internal parts of the connector a shorter overall size connector results.

When desired, the above assembly may be employed with any type of coaxial connector whether it is a screwon, a Snap-on or a slide-on type. Referring to the Snap-on type this invention also provides for a cover shield 16 extending over the fingers 23 of the female end portion of the connector so that the jack 29 of the male connector 11 is guided and aligned by said extended shield 16 during plugging and before it contacts the fingers 23. This shield also serves to receive external bending moments exerted on the fingers 23 from the cable 12 thereby protecting the fingers from being bent out of shape during the plugging and unplugging of the connector parts, or in case of external forces applied on the connector parts while the connector parts are mated.

The invention described may therefore be varied in construction within the scope of the claim, for the particular device selected to illustrate the invention is but one of many possible embodiments of the same. The invention, therefore, is not to be restricted to the precise details of the structure shown and described.

What is claimed is:

A connector for mating two coaxial transmission lines comprising a body having an internally cylindrical surface coaxial to its longitudinal axis, a retaining lip formed circumferentially at one end of and within the internally cylindrical surface of said body, a thread formed externally of said body at the same end, a clamp nut having one end internally threaded operable, to screw on to said external thread of said body, and the other end having an inner conical surface, a ferrule having an outer knurled conical external surface butting against said retaining lip at one end, the outer surface of said ferrule being at a predetermined angle to the longitudinal axis of said body and the inner surface of said clamp nut being at a larger angle to the longitudinal axis of said body then the predetermined angle of said ferrule, and a coaxial cable having a center conductor, an outer conductor, an inner insulation interposed between said conductors, and an outer 5 6 jacket, said outer conductor being covered by said outer 2,552,414 5/51 Eriksen et a1. 174-88 X jacket, said outer conductor and said jacket interposed 2,615,953 10/52 Waite 174--88 between and clamped the inner surface of said clamp nut 2,906,809 9/59 Drenning 174-88 X and the outer knurled conical surface of said ferrule, the 3,097,033 7/63 Felts 174-75 outer surface of said ferrule and the inner surface of said 5 3,107,135 10/ 63 Keil 174--89 X clarnp nut having the differential taper for providing a FOREIGN PATENTS longltudinal locking force between said surfaces due to said differential taper. 232,979 2/61 Austraha- 621,652 6/61 Canada. References Cited by the Examiner 10 654,500 6/51 Great Britain. 904,673 8/62 Great Britain.

UNITED STATES PATENTS 2 449 57 9 4 Violette 174 9 X JOHN BURNS, P T Exammer- 2,460,304 2/ 49 McGee et a1. JOHN P. WILDMAN, DARRELL L. CLAY, Examiners.

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