US3277423A - High-voltage electrical connector - Google Patents

Description

Oct. 4, 1966 J. ROSE HIGH-VOLTAGE ELECTRICAL CONNECTOR Filed May 1, 1963 ATTORNEY United States Patent HIGH-VOLTAGE ELECTRICAL CONNECTOR James Rose, South Lincoln, Mass, assignor to Raytheon Company, Lexington, Mass., a corporation of Delaware Filed May 1, 1963, Ser. No. 277,280 3 Claims. (Cl. 339-91) This invention relates to high-voltage connectors and more particularly to a high-voltage connector for coupling high-voltage wires through the walls of electrical apparatus.

It is often desirable to provide readily removable highvoltage connections to the interior of electrical apparatus. In the past, such connections have usually been made by providing an insulating bushing of generally rod-shaped appearance having a central conductor member running lengthwise through the bushing. The bushing extends through a hole provided in the external wall or metallic chassis of the electrical apparatus and the highvoltage lead is connected to the external end of the central conductor, as by soldering or bolting the high-voltage wire to the central conductor member. The bushing is normally secured to the wall of the electrical apparatus by providing a metallic flange portion on the bushing member, said flange portion being secured to the wall about the periphery of the hole provided in said wall. The remaining end of the bushing central conductor extending into the interior of the electrical apparatus is coupled in a similar manner to the appropriate terminal of the electrical apparatus.

In such prior-art devices the walls of the electrical apparatus are normally at ground or very low potential. Accordingly, a breakdown path for the high voltage is available from the external central conductor member directly to the Wall of the electrical apparatus. By increasing the length of the bushing the breakdown path can be increased, but it is often desirable to have the bushing as short as possible so that the electrical apparatus will fit into confined areas. The farther the bushing extends out of the electrical apparatus, the more susceptible it becomes to inadvertent breakage in shipping and installation. In order to increase the distance of such breakdown path without increasing the length of the bushing, prior-art connectors of this type have been provided with alternate horizontally extending flanges and grooves on the exterior of the bushing so as to increase the surface area of the insulating bushing body and thereby increase the voltage breakdown or creepage path from the external connection to the wall of the electrical apparatus. Dirt and moisture are frequently trapped in these grooves, thus providing a lower dielectric path and impairment of the insulating quality of the bushing. Also, the number of grooves is limited by the diameter and length of the external portion of the bushmg.

In the apparatus of the present invention a much lower breakdown path for the same length of insulator is provided by a novel connector means comprising insulating means having a longitudinal opening therein to accommodate an insulated high-voltage cable; a first stress-distributing member concentric about said opening and having a terminal portion at one end of said longitudinal opening, which portion extends externally of said insulating means, and a second stress-distributing member concentric about said first stress-distributing member. A flange portion is provided on said second stress-distributing member and the connector means of the invention is inserted through the hole in the wall of the electrical apparatus until the flange portion abuts the periphery of said hole. A fastener secures the connector in this position. The high-voltage insulated cable is inserted into the longitudinal opening in the insulator means and electrical connection between the inner conductor of the highvoltage cable and the terminal portion of said first stressdistributing member is made at the terminal end of said longitudinal opening. Accordingly, it will be seen that in the apparatus of the invention, the breakdown path for high voltage comprises the distance extending from the terminal portion of the stress-distributing member along the length of the longitudinal opening plus the usual distance from the start of said opening to the lowerpotential wall of the electrical apparatus.

The apparatus of the invention as thus described in addition to increasing the voltage-breakdown path without the necessity for lengthening the size of the insulator means also prevents the formation of corona in the insulated high-voltage cable. The formation of corona is prevented by connecting the center conductor of the highvoltage cable to the terminal portion of the first stress-distributing member. The first stress-distributing member forms a shield concentric about the high-voltage insulated cable so that essentially all of the electrostatic stresses occur between the first and second stress-distributing members which are insulated from one another by said insulator means which is preferably comprised of a high dielectric strength medium such as ceramic or the like of uniform dielectric constant and is accordingly better able to prevent the formation of corona than the flexible insulator of a high-voltage cable. Other objects and advantages of this invention will become apparent from the following specification taken in connection with the accompaniny drawings in which:

FIG. 1 is a perspective view of the plug member and jack member of the preferred embodiment of the invention shown before connection;

FIG. 2 is a cross-sectional view of the plug and jack members of FIG. 1 in the mated position; and

FIG. 3 is a view of a portion of the apparatus of FIG. 2 showing the high-voltage stress lines.

In FIG. 1 there is shown a connector of the invention comprising a jack member 10 and a plug member 20. Jack member 10 can be seen to comprise in general an outer stress-distributing member 12 concentric about a ceramic or other insulative body 18. Outer stress-distributing member 12 is preferably comprised of a conductive material such as brass, aluminum or the like and is provided with a flanged portion 44 for purposes subsequently to be described. Insulative body 18 is provided with an opening 19 extending longitudinally into the interior of said insulative body so as to provide a receptacle for plug member 20. Plug member 20 is comprised of three main portions, a hollow tubular portion 41, a socket portion 3a and springable fingers 38. Plug member 20 is preferably formed from an insulative material of semi-rigid properties such as nylon, Teflon or the like. High-voltage conductor 11 having an outer insulative portion 13 and an inner conductor portion 32 is inserted through opening 37 in plug member 20 and electrical connection is made between internal conductor 32 and a conductive adapter socket provided in insert 40 of tubular portion 41 in a manner subsequently described in detail in connection with FIG. 2. The plug member 2% is then inserted in the opening 19 in jack member It) and pressed downward into the jack member until springable fingers 38 on plug member 20 make contact with the groove 46 formed in the insulative body 18 of jack member 10. When the plug member 20 is in this position, electrical contact will be established between terminal portion 24 of jack member 10 and internal conductor 32 of wire cable 11 as will now be shown in detail in connection with FIG. 2.

Referring specifically to FIG. 2, there is shown a cross-section of a preferred embodiment of the connector apparatus of the invention in which the plug member 20 and jack member have been mated as previously described and wherein the jack member is shown mounted in place on a panel member 14 of electrical apparatus (not shown). Jack member 10 is affixed to wall 14 by inserting the jack 10 through opening 13 provided in wall 14 and threading nut 16 over threaded portion 17 provided on outer stress-distributing member 12 until O-ring 34 is sufficiently compressed against flange portiqn 44 of outer stress-distributing member 12, thereby to provide a hermetic seal about the periphery of hole 13. It should be noted that the direction of mounting plug member 10 on panel 14 may be reversed by interchanging the positions of the flange portion 44 and threaded portion 17 so that the threaded portion would be on the left side of panel 14 and the flange portion on the right side of panel 14 as viewed in FIG. 2.

In accordance with the preferred embodiment of the invention, the internal conductor 32 of high voltage cable 11 is connected to terminal portion 24 of inner stress-distributing member 26 at the end of longitudinal opening 19 in jack member 10 so as to increase the length of the high voltage breakdown path. Before discussing this connection it is first necessary to consider the detailed construction of plug member 20. As aforementioned, high-voltage cable 11 is inserted through opening 37 in tubular portion 41 of plug member 20. The end of center conductor 32 which extends through tubular portion 41 is formed into the shape of a pin designated as pin 22. Insert 40 has a conductive adapter portion 30 secured on pin portion 22 and fixedly secured in electrical contact thereto as by soldering, crimping or the like. Insert 40 is pressed over adapter portion 30 and secured thereto by extensions 60 and 61 in adapter portion 30 which extend into corresponding ridges in insert 40. Insert 40 is then pressed into opening 37 from open end thereof. The outer diameter of insert 40 is slightly larger than the inner diameter of opening 37; accordingly, a forced fit is secured between the two members and a rigid structure is formed including the insert portion 40 and the wall 41 of plug member 20. The plug member as thus assembled is then inserted into opening 19 of jack member 10 until contact is made between fingers 38 and groove 46. When such contact is established, the end of adapter 31) opposite pin 22 makes contact with jack pin 28 which in turn is in electrical contact with terminal portion 24 of inner stressdistributing member 26. There is thus formed a complete electrical path for high voltage from inner conductor 32 to pin portion 22, to adapter 30, to jack pin 28, and ultimately to terminal portion 24. It is noted at this point that this connection can be readily broken, without the necessity for unsoldering or unbolting, by merely grasping the knurled portion 39 of plug 20 and exerting a suflicient force to the right as shown in FIG. 2 to enable spring fingers 38 to slip out of groove 46 in which case the connection between jack pin 28 and adapter 30 will be broken and plug member 2%) may be readily removed from the longitudinal opening 19 in jack member 10.

In accordance with the invention, an inner stress-distributing member 25 is provided concentric with the longitudinal opening 19 in insulative body 18. Said inner stress-distributing member is comprised of a conductive material such as copper, brass, aluminum or the like and is preferably formed as an integral portion of terminal member 24 and jack pin 28 as shown in FIG. 2. Inner stress-distributing member 26 serves to distribute the high voltage present on lead 32 between the outer stress-distributing member 12 and the inner stress-distributing member 26. The two aforesaid stress- .rlittributing members are insulated from one another A. by insulative body 18 which is preferably of a very high dielectric strength material, such as ceramic, Teflon, epoxy resins, silicone resins or the like. The insulative body 18 is better able to withstand the high electrical stresses caused by the high potential difference between the outer and inner stress-distributing members than the high-voltage cable 12 because of the absence of unequal dielectric constant materials in the medium between the two stress-distributing members. Accordingly, the apparatus of the invention effectively eliminates the formation of corona, and resultant breakdown of insulative material is thereby prevented.

It is further noted that the apparatus of the invention as thus far described provides a greater voltage breakdown path through air for a given connector length than is presently provided in the known prior-art connectors. In the present invention the only breakdown path for high voltage through air is from jack pin 28 along the length of the longitudinal opening 19 in insulative body 18, a length designated L in FIG. 2 and thence from surface 15 of insulative body 18 to surface 21 of outer concentric stress distributing member 12 a distance designated L in FIG. 2. In the prior-art devices wherein connection was made at the external portion of the insulative bushing, the breakdown path for high voltage was at most equal to the distance L plus any small additional distance provided by the knurled configuration of the bushing body. It thus becomes apparent that the apparatus of the invention provides a compact high-voltage connector having a relatively long voltage-breakdown path and inner and outer coronapreventive shields, which connector may be readily connected and disconnected without the necessity for soldering or bolting apparatus.

A further feature of this invention is illustrated in FIG. 3 which is a view of a portion of the connector apparatus of FIG. 2 and shows schematically the highvoltage stress lines present between inner and outer concentric stress members 26 and 12 respectively. As shown in FIG. 3, upon connection of a high-voltage lead to terminal portion 24 of jack member 10, a plurality of stress lines 73 are created between inner concentric stress member 26 and outer concentric stress member 12. By making the length of inner stress member 26 longer than outer stress member 12 so that the inner stress member projects a distance L past the outer stress member the stress lines 73 form a curved trajectory as shown in FIG. 3, said trajectory extending external of insulating member 18. The fact that these stress lines extend external of the insulated member 18 prevents high-voltage breakdown from taking a path along the external surface 74 of insulative member 18 because the high-voltage breakdown path cannot run through or across the stress lines 73. Accordingly, the path must be as shown along the dotted line designated 75. This feature of the invention thereby effectively increases the length of the high-voltage breakdown path since the breakdown path 74 on the external surface of insulative member 18 is much shorter than a corresponding path through air because of the unavoidable buildup of moisture and dust particles and consequent decrease of dielectric strength on surface 74.

This completes the description of the connector apparatus of the present invention. However, many modifications of the invention will be apparent to persons skilled in the art. Also, other methods and devices may be chosen for securing the connector to the panel such as pinning, brazing, soldering, or the like. Accordingly, it is desired that this invention not be limited except as defined by the appended claims.

What is claimed is:

1. A jack member adapted to retain a plug member, said plug member comprised of a hollow tubular insulative portion having a socket portion at one end and 6 having resilient fingers extending from said socket portion in said jack member so that electrical contact is aibout said tubular portion, said jack member comestablished between the end of said inner stress prising: distributing member coupled to said conductor a tubular insulator body having a longitudinal openmeans and the conductive adapter socket of said ing therein to accommodate a high-voltage insulated 5 insert means. wire having an inner conductor and an outer in- 3. Apparatus for coupling high voltage from one sulative portion, said insulator body having an location to another comprising: undercut groove extending about the circumference cable means having an outer insulative sheath and thereof providing a depression for the fingers of an inner conductive wire; said plug member; 10 a plug member comprised of a semi-rigid insulative a first metallic cylinder extending about said longimaterial forming a hollow tubular portion, a socket tudinal opening and having a terminal portion closportion at one end of said tubular portion and ing one end of said opening, said terminal portion resilient fingers extending from said socket portion extending externally from said tubular insulator and overlying said tubular portion; body; insert means extending into said hollow tubular porand a second metallic cylinder extending about said tion and having a conductive adapter socket sefirst metallic cylinder and having a flange extendcured to the inner conductive wire of said cable ing outward from said tubular insulator body. means; 2. Apparatus for coupling high voltage from one 10- and a jack member comprising insulator means havcation to another comprising: ing a longitudinal opening therein to accommodate cable means having an outer insulative sheath and the tubular portion of said plug member, a first an inner conductive wire; stress distributing member concentric about said a plug member comprised of a semi-rigid insulative opening and having a terminal portion at one end material forming a hollow tubular portion, a socket of said longitudinal opening and extending externportion at one end of said tubular portion and ally of said insulator means, and a second stress springable fingers extending from said socket; pordistributing member concentric about said first stress tion and concentric about said tubular portion; distributing member. insert means extending into said hollow tubular portion and having a conductive adapter socket secured to References Cited by the Examiner the inner conductive wire of said cable means; UNITED STATES PATENTS and a jack member comprising an outer stress distributing member, an inner stress distributing memstiemberger 174 142 X bcr insulation means intermediate said stress dis- H945 Nlcholas 174 73 X 2774 812 12/1956 Clark 3392l8 X tributing members and forming a receptacle within said inner stress distributing members to retain the 2967899 1/1961 Pnamggla 174-73 X tubular portion of said plug member, and conductor $051,925 8/1962 Felts 339-.91

means coextensive with the termination of said opening coupled to one end of said inner stress dis- EDWARD ALLEN Prlmm'y Exammer' tributing member, said plug member being inserted ALFRED S. TRASK, Examiner.

Claims (1)

1. A JACK MEMBER ADAPTED TO RETAIN A PLUG MEMBER, SAID PLUG MEMBER COMPRISED OF A HOLLOW TUBULAR INSULATIVE PORTION HAVING A SOCKET PORTION AT ONE END AND HAVING RESILIENT FINGERS EXTENDING FROM SAID SOCKET PORTION ABOUT SAID TUBULAR PORTION, SAID JACK MEMBER COMPRISING: A TUBULAR INSULATOR BODY HAVING A LONGITUDINAL OPENING THEREON TO ACCOMMODATE A HIGH-VOLTAGE INSULATED WIRE HAVING AN INNER CONDUCTOR AND AN OUTER INSULATIVE PORTION, SAID INSULATOR BODY HAVING AN UNDERCUT GROOVE EXTENDING ABOUT THE CIRCUMFERENCE THEREOF PROVIDING A DEPRESSION FOR THE FINGERS OF SAID PLUG MEMBER; A FIRST METALLIC CYLINDER EXTENDING ABOUT SAID LONGITUDINAL OPENING AND HAVING A TERMINAL PORTION CLOSING ONE END OF SAID OPENING, SAID TERMINAL PORTION EXTENDING EXTERNALLY FROM SAID TUBULAR INSULATOR BODY; AND A SECOND METALLIC CYLINDER EXTENDING ABOUT SAID FIRST METALLIC CYLINDER AND HAVING A FLANGE EXTENDING OUTWARD FROM SAID TUBULAR INSULATOR BODY.

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