US3533047A - High voltage coaxial connector - Google Patents

Description

Oct. 6,1970

H. B. MCFARLANE ,3,533,047

HIGH VOLTAGE COAXIAL CONNECTOR Filed April l1, 1969 INVENTOR.

HUGH B. MCFARLANE TTORNE Y 3,533,047 HIGH VOLTAGE COAXIAL CONNECTOR Hugh B. McFarlane, Livermore, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Filed Apr. 11, 1969, Ser. No. 815,372 Int. Cl. H01r 17/18, 7/02 ILS. Cl. 339-94 5 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The instant invention was evolved in the course of, or under, Contract W-7405-ENG-48 with the United States Atomic Energy Commission.

Conventional coaxial cable includes an inner conductor, an insulating sleeve of polyethylene, or the like, coaxially disposed about the inner conductor and bonded thereto, a woven outer or shielding conductor formed concentrically about the insulating sleeve, and an outer jacket of insulating material about the shielding conductor. Connection of such cable to various electrical equipment is commonly accompanied by means of a quick coupling-decoupling coaxial jack connector in order that the cable may be readily connected to, or disconnected from the equipment as desired. A coaxial connector of this type generally includes a plug, or equivalent terminal element, electrically connected to the inner conductor of the cable, and a cap, or equivalent terminal element, electrically connected to the shielding conductor of the cable. The cap is coaxially disposed upon a coaxially extended portion of the insulating sleeve of the cable from which the insulating jacket and shielding conductor have been removed, such extended portion of the sleeve encompassing the end portion of the inner conductor to which the plug is connected. To facilitate electrical connection of the connector terminal elements associated with the cable, to the electrical equipment, the connector typically further includes an insulating body secured to a conductive panel of the equipment, the body having a cylindrical bore in coextensive registration with an aperture through the panel and being provided with a terminal jack at the end of the bore in spaced relation to the panel. The extended portion of the cable sleeve is removably insertable into the bore to removably engage the plug in the terminal jack and thus electrically connect the cable inner conductor thereto. When the plug is thus engaged in the jack, the cap or other terminal element connected to the shielding conductor of the cable is engagable with a complementary terminal element conductively associated with the panel, such as a conductive annular boss projecting from the panel in circumscribing relation to the aperture therethrough. In this manner, the shielding conductor is electrically connected to the panel terminal element.

With a conventional coaxial connector of the type described above, it is to be noted that an air space inherently exists between the coupled inner terminal elements, Le., plug and jack, and coupled outer terminal elements, i.e.,

cap and boss. lIn this regard, the air space is defined by r tred States Patent O 3,533,047 Patented Oct. 6, 1970 ice the annulus between the extended portion of the insulating sleeve of the cable and the bore wall of the insulating body. Thus, the voltage standoff capability of the connector between the coupled inner and outer terminal elements is limited to that of the ionization potential of air. More particularly, if the applied potential between the inner and outer terminal elements exceeds the ionization potential of air, charged particles may be uninhibitedly accelerated the entire length of the air space, causing ionization velocities to be reached and thus ionization breakdown between the terminal elements. As a result, the voltage stand-oli capability of such existing connectors is typically limited to from about 20 to 50 kilovolts.

In order to increase the voltage stand-off capabilities of existing coaxial connectors of the foregoing type, it has been the usual practice to iill the air space separating the inner and outer terminal elements thereof with a medium having good dielectric properties. For example, the air space is typically potted with a solid dielectric material, or filled with an insulating dielectric liquid. Another conventional practice involves pressurizing the air space with a gas having good dielectric properties. However, it will be appreciated that the quick coupling-decoupling feature of the connector is nulliiied by any of the foregoing measures to increase the voltage stand-off capability thereof.

SUMMARY OF THE INVENTION The general object of the present invention is to provide a coaxial jack connector having a quick couplingdecoupling action in conjunction with an outstanding high voltage stand-off capability.

The connector of the invention is generally of the type described hereinbefore wherein coaxially spaced coupled inner and outer terminal elements are separated by an inherently existing intervening annular air space delined between an extended insulating sleeve portion of a coaxial cable and the bore wall of an insulating connector body. However, in accordance with the particularly salient aspects of the invention, the air space is compartmentalized into sealed chambers by a plurality of coaxially spaced O-rings, or equivalent hermetic seals which permit a sliding t between the cable sleeve and bore wall of the connector body. The seals thus do not interfere with the quick coupling-decoupling action of the connector. Yet, by virtue of the sealed chambers thereby provided, acceleration of charged particles the entire length of the air space between the coupled inner and outer terminal elements is effectively impeded. The probability of particles being accelerated to ionization velocities productive of ionization breakdown is materially reduced and hence the voltage stand-off capability of the connector greatly increased.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing is a cross-sectional view taken at a diametric plane through a preferred embodiment of a coaxial connector .in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing in detail, there is shown a quick coupling-decoupling high voltage coaxial connector, in accordance with the present invention, for facilitating connection of a coaxial cable 11, or the like, to electrical equipment which includes a panel 12 of electrically conductive material. The cable is provided with an inner conductor 13, an insulating sleeve 14 of polyethylene, or the like, coaxially disposed about the inner conductor and bonded thereto, a woven outer or shielding conductor 16 concentrically formed about the insulatsleeve, and an outer jacket 1`7 of appropriate insulating material disposed concentrically about the shielding conductor. The shielding conductor and jacket are terminated short of the ends of the sleeve and inner conductor so as to provide a coaxially extended sleeve portion 18 encompassing the end portion of the inner conductor. Longitudinally spaced quick coupling-decoupling connector terminal elements are then provided in connection with the respective ends of the inner conductor and shielding conductor. In this regard, a banana plug 19 is preferably connected to the end of the inner conductor to project coaxially from the end of the extended sleeve portion, which is best tapered, as indicated at 20, for purposes subsequently described. In addition, a conductive cap 21 is preferably coaxially disposed upon extended sleeve portion 18 and connected t0 the end of the shielding conductor longitudinally rearward from the plug. More particularly, a conductive sleeve 22 is advantageously coaxially disposed about the sleeve portion 18 adjacent the end of the shielding conductor. The cap is rotatably coaxially mounted upon the sleeve 22 with an outwardly flared annular flange 23 thereof abutting the inner face of the end wall of the cap. The shielding conductor 16 is secured to the sleeve 22, as by soldering, rearwardly, of the cap. In this manner, the sleeve 22 facilities electrical connection of the shielding conductor to the cap, while permitting cap rotation. The cap is preferably internally threaded, as indicated at 24, for reasons subsequently discussed herein.

The connector further includes terminal elements in association with the electrical equipment for quick coupling-decoupling connection with the plug 1-9 and cap 21 terminal elements of the cable 11. In general, the electrical equipment terminal elements are complementary to the cable terminal elements so as to facilitate releasable conductive engagement thereby. More particularly, there is provided an insulating body 26 of dielectric material, such as a suitable plastic, secured to the conductive panel 12 of the electrical equipment. The body is provided with an elongated bore 27 normal to the panel and in coextensive registration with an aperture 28 therethrough. The bore terminates in a coaxial conductive jack 29, or other terminal element, in spaced relation to the panel and complementary to the plug 19, or other terminal element connected to the inner conductor of the cable. The jack 29 is best recessed into the insulating body 26 and secured thereto as by means of fasteners, such as screw 31. The jack is provided with a lug 32, or is otherwise arranged for convenient connection to the high voltage circuit portion of the electrical equipment.

Electrical connection of the cap 21, or other terminal element connected to the outer shielding conductor 16 of cable 11 to the panel 12 of the electrical equipment is facilitated by a complementary terminal element in electrical connection therewith, in the illustrated case a conductive annular boss projecting from the panel in circumscribing relation to the aperture 28 therethrough. The boss may be defined, for example, by a conductive annular nipple member 34 having an outwardly flared flange 36 secured to the panel about the aperture thereof `with the bore of the member in coextensive registration with the aperture. Securance of the nipple member to the panel may be accomplished by means of suitable fasteners, such as screw 37 extending through the ange and panel into threaded engagement with the body 26. Since in the present case the cap is internally threaded, the boss is externally threaded to facilitate screwed connected of the cap thereon.

It will be appreciated that to the extent thus far described, the coaxial connector is substantially conventional. Quick coupling of the cable 11 to the electrical sleeve portion 18 through the bore of the nipple member 34 and panel aperture 28, into the bore 27 of the body 26 to removably engage plug 19 in terminal jack 29. Cap 21 is screwed upon the nipple member 34 to thereby complete the connection. It is particularly important to note that an annular air space inherently exists between the periphery of the extended sleeve portion 18 and wall of the bore 27. Such air space separates the coupled inner and outer terminal elements, i.e., separates the coupled plug and jack from the coupled cap and nipple. Typically an applied high voltage exists at the coupled inner terminal elements while the coupled outer terminal elements are at ground potential. In other words, the inner and outer terminal elements are oppositely polarized, and a potential gradient exists therebetween through the air space. Normally, the potential gradient would be effective to accelerate charged particles, such as stray electrons, the entire length of the air space. The applied voltage would consequently be limited since the particles may be unimpededly accelerated to ionization velocities. Such accelerated particles would undergo ionizing collisions with gas molecules in the air space and cause ionization breakdown between the inner and outer terminal elements. The high voltage stand-off capability of the connector would thus be normally limited. Although the stand-off capability may be increased by filling the air space with high dielectric material, the quick couplingdecoupling feature of the connector is then lost.

In accordance with the particularly salient aspects of the invention, the high voltage stand-off capability of the connector is materially increased while the quick coupling-decoupling feature is retained. In this regard, the air space is compartmentalized into a longitudinal succession of sealed chambers 38 by a plurality of coaxially spaced resilient O-rings 39, or equivalent hermetic seals which permit a sliding iit between the extended sleeve portion 18 and Wall of bore 27. The O-rings are preferably partially recessed into circumferential grooves 41 provided in the wall of bore 27, or alternatively into circumferential grooves provided in the periphery of extended sleeve portion 18. In either case, the O-rings permit slidable insertion of the extended sleeve portion into the bore to facilitate quick coupling engagement of the inner and outer terminal elements, and are slightly compressed to provide the compartmentalizing hermetic seals in the air space. The O-rings may be coated with a silicone grease, or the like, to further enhance both their sealing action and sliding action. The tapered end 20 of the extended sleeve portion is of further assistance in facilitating the ready slidable insertion thereof into the bore.

With the air space thus compartmentalized by the O-rings 39 into the succession of sealed chambers 38 between the coupled inner and outer terminal elements, it will be appreciated that the probability of ionization breakdown is materially minimized. More particularly, the distance over which a particle may be accelerated by the potential between the coupled inner and outer terminal elements is now limited to the length of each chamber 38. Consequently, the velocity to which a particle may be accelerated is proportionately reduced and the voltage that may be applied between the inner and outer terminal elements without causing ionization velocities to be attained is increased. As a result the voltage stand-off capability of the connector is materially increased. In actual practice increases in the stand-off capacity of at least 300% are readily obtainable with connectors in accordance with the present invention.

I claim:

1. A coaxial connector comprising a coaxial cable having an inner conductor, an insulating sleeve coaxially disposed about the inner conductor and bonded thereto, an outer conductor concentrically formed about the sleeve, and an insulating jacket concentrically disposed about the outer conductor, said sleeve including an extended portion encompassing an end portion of said inner conductor and projecting coaxially from an end portion of said outer conductor and jacket, inner and outer quick coupling-decoupling cable terminal elements respectively electrically connected to said end portions of said inner and outer conductors, said outer terminal element spaced longitudinally rearward from said inner terminal element, an insulating body projecting from a conductive panel of electrical equipment, said body having an elongated bore normal to the panel and in coextensive registration with an aperture therethrough, a quick coupling-decoupling equipment inner terminal element disposed at the end of said bore in spaced relation to said panel and adapted for connection to electrical circuitry of said equipment, a quick coupling-decoupling equipment outer terminal element electrically connected to Said panel and disposed about said aperture, said inner and outer equipment terminal elements respectively complementary to said inner and outer cable terminal elements and releasably engaged thereby with said extended sleeve portion coaxially disposed within said bore and deiining With the Wall thereof an annular air space separating the engaged inner and outer terminal elements, and hermetic seal means disposed within said space to compartmentalize same into a longitudinal succession of sealed chambers while permitting a sliding t between said extended sleeve portion and the Wall of said bore.

2. A coaxial connector according to claim 1, further dened by said hermetic seal means comprising a plurality of coaxially spaced resilient O-rings partially recessed into circumferential grooves formed in the Wall projecting coaxially from the end of said inner conductor and extended sleeve portion, said equipment inner terminal element being a jack coaxially disposed at the end of said bore and releasably engaged by said plug, said cable outer terminal element being a cap coaxially disposed upon said extended sleeve portion, and said equipment outer terminal element being an annular boss projecting from said panel in circumscribing relation to said aperture and releasably engaged by said cap.

4. A coaxial connector according to claim 3, further defined by said hermetic seal means comprising a plurality of coaxially spaced resilient O-.rings partially recessed into circumferential grooves formed in the wall of said bore and compressively engaging the perpihery of said extended sleeve portion.

5. A coaxial connector according to claim 4, further defined by said extended sleeve portion having a tapered end terminating at said plug.

References Cited UNITED STATES PATENTS 2,296,766 9/ 1942 Bruno 174-22 2,442,545 6/1948 Koch et al. 174-152 2,496,938 2/ 1950 Friedman 174-84 2,625,579 1/1953 Frazee 174-77 3,319,211 5/1967 Smith et al 339-31 STEPHEN J. NOVOSAD, Primary Examiner of said bore and compressively engaging the periphery 80 L. I. STAAB, Assistant Examiner of said extended sleeve portion.

3. A coaxial connector according to claim 1, further defined by said cable inner terminal element being a plug

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