US3509516A

US3509516A - High voltage connector and entrance bushing assembly

Info

Publication number: US3509516A
Application number: US702309A
Authority: US
Inventors: Davis M Phillips
Original assignee: McGraw Edison Co
Current assignee: Cooper Industries LLC
Priority date: 1968-02-01
Filing date: 1968-02-01
Publication date: 1970-04-28
Anticipated expiration: 1987-04-28

Description

April 28, 1970 D. M. PHILLIPS HIGH VOLTAGE CONNECTOR AND ENTRANCE BUSHING ASSEMBLY Filed Feb. 1, 1968 a2 a/ 5 42 59 50 r 6/ II \III I II 5 7 INVENTOR.

Dal 4'5 (/7. Phi ZZL' p5 flttorng/ United States Patent O U.S. Cl. 339-94 17 Claims ABSTRACT OF THE DISCLOSURE An electrical entrance bushing and cable connection assembly including a recessed entrance bushing for an enclosed device such as a transformer, a terminally recessed cable connector having a central conductor portion, and an interposed adapter closely fitting the recessed portions of the bushing and connector. The adapter further includes enclosed arc extinguishing means associated with the central conductor.

BACKGROUND OF THE INVENTION This invention relates to entrance bushings and associated separable connectors for high voltage conductors such as shielded electrical cables.

The prior art includes entrance bushings and associated connectors as shown in Patent No. 3,307,137, issued to L. J. Tordoif et al. on Feb. 28, 1967, and copending application Ser. No. 571,495 by W. J. Weinfurt et al., filed Aug. 10, 1966, now Patent No. 3,401,370, both the patent and application being assigned to the present assignee. The Patent No. 3,307,137 shows a frusto-conically recessed entrance bushing with a mating frusto-conically extending releasable connector. On the other hand, the aforementioned copending application shows an extending bushing with a mating recessed connector. The latter combination further includes arc extinguishing means within the bushing. In the latter design, the extending insulating members may be susceptible to breakage. Further, the replacement of the arc extinguishing means would ordinarily require replacement of the entire entrance bushing.

SUMMARY OF THE INVENTION It is, therefore, an object of the invention to provide an entrance bushing and connector assembly with improved resistance to breakage.

It is another object of the invention to provide an assembly of the aforedescribed type in which the are extinguishing means is easily field replaceable.

It is another object of the invention to provide an assembly of the aforcdescribed type in which the elements are readily adaptable to be assembled in various combinations to thereby increase the usefulness of the individual elements.

It is still another object of the invention to provide an entrance bushing for a sealed enclosure which permits replacement of connector elements or change of connector types without breaking the seal of the enclosure.

Other objects and advantages of the invention will become apparent upon reading the following description.

These objects are accomplished by providing a recessed bushing, a recessed releasable connector, and an interposed resilient, sealing and insulating adapter which extends into the recesses of both the bushing and connector. The adapter further includes axially extending conductor and contact means to connect the conductor of the bushing to the conductor of the connector.

. In addition, the adapter is releasably fastened to the bushing and contains arc extinguishing means effective to extinguish arcs between the conductor of the adapter and 3,509,516 Patented Apr. 28, 1970 the conductor of the connector when the connector is removed from the assembly with an electrical load on the conductors.

The adapter is made easily removable to facilitate field replacement.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a partially sectional View taken generally on the center line of an assembly embodying the present invention; and

FIGURE 2 is a partially sectional fragmentary elevation view of several elements used to accomplish a modification of the device shown in FIGURE 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawing, FIGURE 1 shows an assembly consisting of three major portions, a releasable connector 2, an adapter 3 and an entrance bushing 4.

The connector 2. is more completely described in the aforementioned application Ser. No. 571,495. Connector 2 has an exterior rigid magnetic metal shell or housing 5 consisting of two generally cylindrical portions having their axes disposed at right angles to one another. Centrally located within connector 2 is an inner conductive member 6. The inner conductive member 6 is radially spaced from shell 5 and retained in position by epoxy material that is cast about the inner conductive member 6 by introduction through an opening 7 in shell 5 so as to form a generally tubular insulating member 8 between shell 5 and inner conductive member 6. Extending inwardly from the principal openings in the ends of shell 5 are frusto-

conical recesses

9 and 10 which extend from the open ends of connector 2 through the tubular insulating member 8 to provide continuous conical surfaces which terminate in the open ends of inner conductive member 6. Recess 10 is separated from recess 9 by a wall 11 within the inner conductive member 6. A threaded aperature 12 extends through wall 11 and is coaxial with conical recess 10. A silver-coated contact stem 13 has a threaded portion 14 which is received within the threaded aperture 12 in wall 11. Adjoining threaded portion 14 there is a portion 15 of square cross section which provides wrench flats for assembling stem 13 to the inner conductive member 6. A silver-coated cylindrical contact portion 16 extends downwardly. At the distal end of stem 13, there is attached a cylindrical insulating rod follower 17 which assists in extinguishing arcs occurring when contact portion 16 is disconnected by withdrawal under electrical load. Follower 17 is formed of an insulating material which in the presence of an arc responds by emitting an arc snufling gas.

The threaded portion 14 of stem 13 projects through wall 11 and inner conductive member 6 to engage the end of an inner conductive member 18 of a cable 19. Stem 13 is turned tightly so that the inner end of threaded portion 14 securely clamps the end of conductor 18 against the inner surface of conductive member 6.

A cable 19 includes the inner conductor 18 of copper or aluminum which is surrounded by an insulting sheath 20, preferably made of high molecular weight polyethylene. A layer of flexible semiconductive material 21 surrounds sheath 20. A number of tinned copper concentric neutral wires 22 are wound helically about layer 21.

Cable 19 is terminated by cutting back sheath 20 to expose the terminal end of conductor 18 which extends into inner conductive member 6. Conductive layer 21 is removed for a length sufficient to permit a resilient insulating gland 25 to be slipped over the end of cable 19 in contact with sheath 20. The outer surface of gland 25 is shaped in the form of base-to-base frusto-conical surfaces which fit respectively tightly within frusto-conical recess 9 and within the opposing frusto-conical inner surface of a compression and electrical stress relief cone 26. A plurality of screws, such as screw 27, serve to draw the conductive metallic cone 26 toward the main body of connector 2 to compress gland 25 therebetween to form a tight seal about sheath 20. The reduced end 28 of cone 26 fits closely about layer 21 of cable 19. Conductors 22 are clamped about the periphery of end 28 by a circular clamp 29, and the ends thereof must be grouped and connected to a convenient ground point (not shown).

A loop 30 extends from the top of connector 2 to facilitate the handling of connector 2 with a hookstick.

Entrance bushing 4 is munted within an aperture 31 in the sheet metal wall 32 of an enclosure of an electrical device such as a transformed (not shown). Bushing 4 has an elongated frusto-conical body 33 made of rigid electrical insulating material such as epoxy resin. A flange 34 is formed about the periphery of the upper end of bushing 33. An elastic sealing gasket 35 is placed in an annular groove in the lower surface of fiange 34.

A circualr hold-down plate 38 which has turned down peripheral edges engages the upper surface of flange 34 and it is securely fastened to Wall 32 by a plurality of screws or bolts (not shown) to securely hold bushing 4 within aperture 31 and compress gasket 35 into sealing engagement with wall 32. A plate 39 having a central aperture to accommodate adapter 3 is fastened to the top of hold-down plate 38 by a plurality of screws, such as screw 40. A spring loaded bail 41 has its ends fastened to plate 39 to hold connector 2 in firm engagement with adapter 3 in a manner more completely described in the aforementioned application Ser. No. 571,495.

Bushing 4 has an open-topped central axial bore comprising an upper frusto-conical portion 42 and a lower concentric cylindrical portion within a cylindrical metallic shielding tube 43. The lower edge of tube 43 is soldered to the upper periphery of a conductive metallic sleeve 44 which is also imbedded in the insulating body 33 of bushing 4. A conductor rod 45 is threaded into the lower end of sleeve 44 and extends axially through the bottom of bushing 4 to terminate in a threaded portion 46 to which conductors may be attached.

Adapter 3 includes an encircling resilient insulating sealing gland 48 consisting generally of two base-to-base frusto-conical portions. An upper frusto-conical portion 49 fits tightly within frusto-conical recess in connector 2. The opposite frusto-conical portion 50 similarly conforms to the fursto-conical bore portion 42 of bushing 4. At the juncture of these two frusto-conical portions a skirt portion 51 extends laterally and turns downwardly at its periphery to bear on the upper surface of plate 39. Skirt 51 serves to prevent dirt or other contaminants from entering the assembly, particularly between the frustoconical surfaces of gland portion 50' and bushing recess 42.

It is contemplated that the surfaces of

recesses

10 and 42, as well as portions 49' and 50, could have a shape other than frusto-conical.

The central axially extending cylindrical bore of gland 48 fits tightly over an assembly of cylindrical shape which includes contact means and arc extinguishing means. A conductive metallic enclosing and shielding tube 52 extends from near the upper end of gland 48 through the central bore of gland 48 and extends a substantial distance below the lower end of gland 48. A rigid plasic sleeve 53 is threaded into the upper end of tube 52 and terminates'flush with the upper end of gland 48. The central bore of sleeve 53 loosely accommodates the lower end of contact stem 13. Sleeve 53 is similar to rod follower 17 in that it is made of a material which emits an arc extinguishing gas when exposed to an are formed upon withdrawal of contact stem 13.

A contact stud 54 fits closely within the lower end of tube 52 and is pinned thereto by a pin 56 which fits tightly within aligned diametrical apertures in tube 52 and stud 54. A threaded portion 57 extends from the lower end of stud 54 to engage the threaded bore of sleeve 44 and thereby removably secure adapter 3 within bushing 4. A portion of reduced diameter 58 extends from the upper end of stud 54. A screw driver slot is formed in the upper end of portion 58 to facilitate the fastening of stud 54 to sleeve 44. An upwardly extending tubular tulip-type contact tube 59 fits over and is soldered to the periphery of portion 58. The upper slotted end of contact tube 59 is surrounded by a helical spring 60 which exerts an inwardly directed force on contact tube 59 to provide contact pressure between contact tube 59 and the contact portion 16 of stem 13.

A pair of diametrically opposite apertures 61 are formed in shielding tube 52 to provide for high pressure gas venting in the event contact 16 is closed to contact 59 under fault conditions. Under such conditions an arc would form at the upper end of contact tube 59 and would be of such strength as to result in the sudden formation of large amounts of gas, particularly because of the presence of the arc emitting substances of follower 17 and sleeve 53. This high pressure gas would tend to blow connector 2 upwardly. Apertures 61 open a pressure relief path whereby the gas may pass downwardly between contact 59 and tube 52 and thence through apertures 61. The pressure of the gas is sufficient to force the lower frusto-conical end 50 of gland 48 upwardly to allow the gas to escape between gland 48 and surface 42.

. In installations where the convenient disconnect ability and arc extinguishing capacity of the device shown in FIGURE 1 is not needed, the construction of entrance bushing 4 and the cable terminating assembly comprising gland 25 and stress cone 26 permits a simple, more economical and more permanent modification of the assembly in which the termination of cable 19 is inserted directly into entrance bushing 4, as shown in FIGURE 2. In order to accomplish this modification, adapter 3 is removed from entrance bushing 4 by turning threaded portion 57 of contact stud 54 from sleeve 44 and lifting adapter 3 upwardly from bushing 4. Plate 39 and bail 41 are removed by removing screws 40 from hold-down plate 38. The termination of cable 19 is removed from connector 2 by removing screws 27 and turning pin 13 to free the end of conductor 18. The cable termination as sembly, including gland 25, is then free to be removed from connector 2.

It is obvious that the connection assembly of cable 19 to entrance bushing 4 may be prepared by the aforedescribed modification of the assembly of FIGURE 1 or may be prepared initially with only entrance bushing 4 and the elements of the termination assembly on cable 19.

The end of conductor 18 is prepared by placing a strain relief washer 63 over the end of conductor 18, as shown in FIGURE 2, and crimping a male contact member 64 over the end of conductor 18. A female contact member 66 is threaded into and tightly turned into sleeve 44. The upper slotted end of contact 66 is surrounded by a spring 67 which exerts inwardly directed force to provide contact pressure. The connection is then made by inserting the terminal end of cable 19 into entrance bushing 4 until contact 64 engages contact 66, as shown in FIG- URE 2. Screws 27 replace screws 40 in hold-down plate 38 to fasten stress cone 26 to hold-down plate 38 and are turned tightly to compress gland 25 firmly within frusto-conical recess 42 of bushing 4.

While the embodiment heretofore described is adapted to fulfill the objects stated, it is to be understood that it is not intended that the invention be confined to the particular embodiment disclosed since it is susceptible of various modifications.

I claim:

1. A high voltage cable connection apparatus comprising:

a cable terminating connector comprising a first electrical insulating portion surrounding a first central conductor, a first recess formed in said connector and extending inwardly into said connector, and first contact means connected to said central conductor,

said first contact means comprises a contact pin extending from said first central conductor at the inward end of said first recess toward the outer opening of said recess;

an insulating bushing for being mounted in a wall of an electrical appartus enclosure and for providing a conductive path therethrough comprising a second electrical insulating portion surrounding a second central conductor, and a second recess formed in said bushing;

adapter means comprising an insulating body having extending portions which respectively fit closely within said first and second recesses, and conductor means disposed within said body for providing a conductive path between said first central conductor means and said second central conductor means comprising connection means for making electrical connection with said second central conductor, and second contact means for making releasable contact with said first contact means; and

a conductive shield surrounding said first and second contact means within said adapter means and a pressure releif aperture formed in said shield for permitting gas produced upon occurrance of arcs between said first and second contact means to pass to the outside of said adapter means and to escape from said connection apparatus between said adapter and said insulating bushing.

2. The invention as defined in claim 1, together with means for releasably fastening said connector to said electrical apparatus enclosure and compressing said insulating body between said connector and said bushing.

3. The invention as defined in claim 1 in which said second central conductor and said connection means comprise interengaging threaded means, whereby said connection means is removably fastened to said second central conductor to thereby fasten said adapter means to said bushing.

4. The invention as defined in claim 1 in which said adapter means comprises said elongated tubular shield surrounding said first and second contact means and connected to said connection means for shielding internal voids from electrical stresses.

5. The invention as defined in claim 1, together with arc extinguishing means within said adapter means for extinguishing arcs occurring upon separation of said first contact means from said second contact means.

6. The invention as defined in claim 5 in which:

said first contact means comprises an elongated member extending into said adapter means to make contact with said second contact means; and

said arc extinguishing means comprises a sleeve of material which emits an arc extinguishing gas when exposed to an arc and which is mounted Within said adapter means to surround said first contact means adjacent to the end of said second contact means where said first contact means separates from said second contact means to form an are.

7. A high voltage cable connection apparatus comprising:

a cable terminating connector comprising an outer conductive cover and a first electrical insulating portion inside said housing and surrounding a first central conductor, a first frusto-conical recess in said con nector formed in said first insulating portion and extending inwardly to a generally truncated apex in said connector, and first contact means connected to said central conductor; an insulating bushing for being mounted in a conductive wall of an electrical apparatus enclosure and for providing a conductive path therethrough comprising a second electrical insulating portion surrounding a second central conductor, and a second frusto-conical recess formed in said second insulating portion and extending inwardly to a generally truncated apex at said second central conductor; adapter means comprising an elastic insulating body having a centrally positioned laterally extending annular flange between said cable terminating connector and said insulating bushing, and having oppositely extending frusto-conical portions which fit respectively closely within said first and second recesses; and

conductor means disposed within said body for providing a conductive path between said first central conductor means and said second conductor means comprising connection means for making electrical con nection with said second central conductor, and second contact means for making releasable contact with said first contact means.

8. The invention as defined in claim 7, together with means for releasably fastening said connector to said electrical apparatus enclosure and compressing said elastic insulating body between said connector and said bushing.

9. The invention as defined in claim 7 in which said second central conductor and said connection means comprise interengaging threaded means, whereby said connection means is removably fastened to said second central conductor to thereby fasten said adapter means to said bushing.

10. The invention as defined in claim 7 in which said adapter means further comprises an elongated tubular shield surrounding said first and second contact means and connected to said connection means for shielding internal voids from electrical stresses.

11. The invention as defined in claim 7 in which said first contact means comprises a contact pin extending from said first central conductor at the inward end of said first recess toward the outer opening of said first recess.

12. The invention as defined in claim 11, together with are extinguishing means for extinguishing arcs occurring upon separation of said first contact means from said second contact means.

13. The invention as defined in claim 12 in which:

said are extinguishing means comprises a sleeve of material which emits an arc extinguishing gas when exposed to an arc and which is mounted within said adapter means to surround said first contact means adjacent to the end of said second contact means where said first contact means separates from said second contact means to form an arc.

14. An adapter device for assembly between a first connection device having a first central conductor and a second central conductor, said first and second connection devices having first and second recesses respectively formed in insulating material surrounding said first and second central conductors, said first and second recesses being opened to the exterior of said first and second devices and tapered to a termination of reduced cross sectional area at said first and second conductors, said adapter device comprising:

an elastic insulating body having oppositely extending portions which fit closely within said first and second recesses, respectively, said insulating body further including an integral skirt portion extending laterally from said body at the junction of said oppositely extending portions, said skirt portion serving to prevent entry of contaminants between said body and one of said connection devices; and

conductor means disposed within said body for providing a conductive path between said first and second central conductors, said conductor means comprising releasable electrical connection means for making electrical releasable connection with said first and second central conductors.

15. The invention as defined in claim 14 in which said first and second recesses are of frusto-conical shape, and said elastic insulating body comprises base-to-base frustoconical portions. 16. The invention as defined in claim 15 in which said conductor means is disposed within a central aperture in said body extending between the truncated apexes of said frusto-conical portions.

17. The invention as defined in claim 16 together with an insulating sleeve encircling said central aperture at one end of said conductor means, said sleeve being made of a material which emits an arc extinguishing gas when exposed to an electrical arc.

8 References Cited UNITED STATES PATENTS Link 339' 11'1 FOREIGN PATENTS 8/ 1940 Germany. 12/ 1956 Germany.

5/ 1963 Great Britain.

15 MARVIN A. CHAMPION, Primary Examiner J. H. MCGLYNN, Assistant Examiner US. Cl. X.R.