US3153114A - Bushing assembly for electrical apparatus - Google Patents

Description

Oct. 13, 1964 A. s. LINDwAY ETAL 3,l53,114

BusHING AssEMBLY FOR ELEc'rRIcAL APPARATUS Filed Jan. 24. 1962 United States Patent O 3,153,1M BUSHNG ASSEMELY FR ELECTRCL AiblAff/TUS Andrew S. lLindway .and .Iohn MI. Anderson, Pittshurgh,

Pa., assignors to Aiiis-Chainiers Manufacturing Cornpanfl, Milwaukee, Wis.

Filed Ian. 24, 13%2, Ser. No. 169,706 Ki Ciarns. (Cl. 1714-43) This invention relates to electrical insulating bushings and in particular to insulating bushings rnounted in a tank containing an electrical apparatus innnersed in a dielectric liquid.

In a number of instances it is standard practice to house an electrical apparatus in a tank substantially filled with a dielectric liquid. The common example is a distribution transforrner contained in an oil filled tank. The electrical leads to the transforrner are brought through the tank walls and require insulating bushings at their points of entry. These bushings may be made of a ceramic material such as porcelain and consequently, are subject to damage in the field. In structures of the prior art, replacement of a damaged bushing has not been a simple task. Freqnently, it is necessary to locate the insulating bushings below the level of the dielectric liquid in the tank containing the apparatus. Consequently, replacement of the damaged bushing first calls for renioving the dielectric liquid from the tank to a level below the insulating bushing. If the liquid is not partially removed from the tank it is apparent that it would leak through the opening in the tank wall after the bushing has been removed.

The above type of transforrner also normally uses protective fuses. These fuses may comprise a part of the electrical leads attached to the windings of the transformer. In order that the fuses are partially responsive to the temperatures of the dielectric liquid, they are placed within the transformer tank and subrnerged in the dielectric liquid. It is, of course, to be expected that these fuses will have to be replaced occasionally while the transformer is in the field. The manner in which these fuses can be replaced is somewhat related to the above described problem of replacing damaged insulating bushings. A conventional means for gaining access to the protective fuse is the provision of a handhole in the cover of the transformer tank. The handhole has a removable cover and the maintenance man may remove this cover and then fish for the damaged fuse which is positioned below the level of the oil. An atternpt to gain access to the fuse through the side of the tank would mean partial draining of the oil.

Our invention comprises a novel bushing arrangement which simplifies both of the above described problems of replacing damaged bushings and protective fuses. Briefly described, our bushing comprises two Sections through which an electrical lead extends. When the external section of the bushing requires replacement, its removal causes a biased means coupled to theelectrical lead to be released. The released biasing means forces a sealing device which is also mounted on the electrical lead to seal off all openings in the interior bushing section through which the dielectric liquid would otherwise escape. The protective fuse may form a removable section of the electrical lead and thereby easily be replaced while the sealing means prevents leakage of the dielectric liquid.

lt is, therefore,,one object of this invention to provide a new and improved insulating bushing.

Another object of this invention is to provide a new and improved means for readily replacing the exterior portion of the damaged insulating bushing.

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Another object of this invention is to provide a new and improved means for readily replacing the protective fuse contained within an electrical apparatus.

Objects and advantages other than those mentioned above will become apparent upon readint7 the description in connection with the drawing in which:

FIG. 1 illustrates an electrical apparatus containing a bushing of this invention;

FIG. 2 is a view of the bushing and fuse arrangement of this invention taken in section along its axis;

PIG. 3 is a sectional view taken along' line iii-Hi of PIG. 1; and

' FIG. 4 is a sectional view of the bushing and fuse arrangement of this invention in a modified form.

Referring to FIG. l, a distribution transformer lit is illustrated containing an insnlating bushing 12 which is horizontally mounted below the level of `a dielectric liquid 14 in a tank 16. As can be seen from the detailed illustration of PIG. 2, the bushing 12 comprises an exterior section 18 and an interior section 19. The eX- terior section may be mounted to a wall 21 of the tank through a conventional clamp 23 and bolts 24 (see FIG. 3) and sealcd about an opening 26 of the wall by a gasket 27 which is compressed when the bolts and clamp are secured tightly. The interior section 19 may have fianges 29through which bolts 30 extend for engaging threaded lugs 31 on the interior side of the tank wall 21. The interior bushing section 19 is forced against a gasket 32 for preventing oil leakage at its junction with the tank wall. Both bushing Sections are hollow in order to receive an electrical conductor 34 which partially comprises a rigid rod 36 with a threaded end 37. The rod 36 is maintained in its relative position with the exterior bushing section 18 by means of an annular cap 39 whichis in sealing engagernent with the bu'shing and a nut dt) which is threaded on the rod 315 against the cap. `Also threaded on the rod is a connector 42 to which a flexible lead 44 is connected. A gasket 45 is seated between cap 39 and bushing section 18.

The electrical conductor 34 within the two bushing Sections further comprises a removable protective fuse 4G with one end secured to the rod 35 by a removable roll pin 47. The other end of the fuse has a conventional right angle slotted groove or track 50 for engaging a lug 51 in anelectrically conductive fuse holder 53. Connected to the opposite end of the fuse holder is a transforrner winding lead 54.

At an intermediate point in the fuse holder 53 a means 55 has been provided for securing it to a truncated, conical or tapered insulating sleeve 57. The end 59 of the fnse holder is slidably mounted in the end 6% of the interior section through an opening 61. Fuse holder end 51? may be hexagonally shaped to prevent any relative rotation with end 'titi and its opening ef which is also hexagonal. A biased spring is positioned between an extension od of the inner bushing section 19 and the broad end 65 of the sleeve 57. This spring is inaintained in its biased condition by the action of the nut 4d on the condnctor rod 36. Holes 66 displaced along the longitndinal, surfaces of the bushing interior section w and the sleeve 57 perrnit the passage of oil. Consequently, fuse is surrounded by the oil and is subject to the temperature of the oil, a desirable feature. It is apparent that if the outer bushing section is removed and the sleeve and inner bushing section reman inptheir illustrated positions, oil will pass through the holes 65 in these two members and leak through the opening 26 in the tank wall. .Thus, it becomes necessary to seal off all entry spaces in the interior bushing section 19.

Assuming that the exterior bushing section lt; needs Co be replaced, the above sealing requirements can be awaria accomplished in the following manner. The threaded connector 42. is first removed from the conductor rod 36 and then the nut 40 is backed off and removed. Recalling that the Spring 63 is in a biased condition it can be Seen that a force is exerted to the right or inwardly on the electrical conductor through the hollow sleeve 57 and fuse holder 522. Thus, as nut :to is baclted off spring 63 expands and, since it is coupled to the conductor through slceve 57, the conductor is moved inwardly until the sleeves outer surface makes contact with the inner surface 69 of the interior bushing section. The dimensions of the sleeve and interior 'eushing section are So designed as to pcrmit physical contact with each other only after each covers the holes od in the other. T hus, entrance of the oil through the holes in the interior section and sleeve is blocked. While oil may enter through the interior bushing section end od, further transmittal of this is blocked by the abutment of the Sleeve against end oil.

After nut 4% has been removed from conductor rod TK and a sealing action has been achieved, disassembly of the extcrior bushing section ll and its Cap may commence. Upon removal of the clamp bolts, a new bushing section may then be installed. Retightening the nut 40 causes the conductor 34 and its fuse 46, along With the hollow sleeve 57, to be moved outwardly against the spring 63 to bias it and permit entry of oil through the holes If it is only necessary to replace the protective fuse 46 and not the bushingls exterior section the above Steps for obtaining a Sealing action are repeated while the exterior section iS still clamped to the tani: wall The conductor rod So is then rotatcd a quarter of a turn through the provision of a slot '71 at its end. This rotation disengages the fuse from its fuse holder S3 and the rod and its connected fuse may then be removed from the bushing. The roll pin 47 is relnoved and a new fuse connected to the rod. The rod and its connected fuse are then ready for reassembly in the bushing.

The modified bushing arrangement shown in FlG. 4 has, as one significant difference, the fact that it is designed only for externally replacing the protective fuse 46 and is not designed for replacement of the exterior bushing section 18 in a manner similar to the above arrangement.

Another difference is that the interior Section 19 does not have any circulating holes do and the oil which comes in contact With the protective fuse enters only through end oil of the section 19. Consequently, there is no need for the hollow Sleeve 57 of the bushing shown in PIG. 2. Since the exterior bushing section 18 is not intended to be replaced without lowering the level of the dielectric liquid, there is no need for the interior section 19 to abut in a sealing arrangement with the tanlr wall In fact, it is conceivable that one could combine the two Sections into an integral unit without departing from the spirit of this invention.

At the end 6d of the interior section 19 a recessed Shoulder '73 is provided. Positioned on this Shoulder is a biased spiral compression spring 63' which is coupled to the conductor 34 by a washer 'F5 and several nuts 76 threaded on a conductor stud *29. The conductor stud is of a size to freely move in an axial direction through end 6d of the interior section and the washer 75. The conductor Stud '79 has a Shoulder Et) for bearing against a gasket S2 which is mounted about the Stud end The fuse holder 53 is threaded on end i of the Stud. lt is to be noted that a pair of projections 85 extend from opposite sides of the fuse holder. These projections engage with longitudinal grooves in the interior busning section 19. The combination of the projections 85 in grooves S6 prevents rotation of the fuse holder when the conductor rod 36 is being rotated to disengage the fuse 46 from its holder 53.

Replacement of a blown fuse is substantially the same as in the first described bushing structure. Upon removal of the nut 4d the spring 63 exnands and causcs its adjacent washer and the conductor to move inwardly to the right. This movement is stop-ped when the gasliet S2 is in contact with end of) of the inner section This prevents all passage of oil through oeening 26 in the tank wall and permits one to replace the protective fuse with relative ease.

While only two embodiments of this invention have been illustrated and described, it will be apparent to those skilled in the art that additional modifications may be made without departing from the Spirit of this invention and the scope of the appended claims.

l-laving now particularly described and ascertained the nature of our said invcntion and the manner in which it is to be performcd, we declare that what we claim is:

1. A bushing of the type that cxtends in Sealing relationship through the wall of a tank containing electrical apparatus immersed in a dielectric liquid, comprising,

a hollow exterior extension mountable outside the tank,

a hollow interior extension mountable inside the tank, said interior extension having an inwardly tapering surface, said surface having a hole connecting the interior of the bushing to receive dielectric liquid from the tank,

a conductor cxtending through said bushing cxtensions in an axially slidable relationship,

sealing means axially movable within said interior extension between inward position and an outward position, said sealing means comprising a hollow sleeve having an outer Surface and a hole on said surface for admitting the liquid; said outer surface being Shaped to be parallel t said inner surface and to be spaced from said inner surface When said sleeve is in said outward position and to abut said inner surface to close the interior of said bushing from said tank when said sleeve is in its relatively inward position,

means on said conductor for engaging said sealing means whereby said sealing means is positionable according to the axial position of said conductor,

ias means mounted between said interior extension and said sealing means to urge said sealing means inwardly, and

exteriorly accessible means for fastening the outer end of Said conductor to said exterior extension, said means being opera'ole during unfastening to release said conduetor to move inwardly whereby said bias means positions said sealing means to Seal the interior of said bushing from said tank, Said means being operable during fastening to move said conductor outwardly whereby Said sealing means is positione to admit liquid from Said tank to Said bushlng interior.

2. A bushing according to claim 1 in which said bias means comprises a spiral spring encircling said conductor and positioned between a fiange of Said interior extension and an end of Said slceve.

3. A bushing according to claim 1 in which said conductor includes a removable fuse.

4. A bushing according to claim 1 in which said exteriorly accessible fastening means maintains said bushing substantially sealed until Said conductor has been released sufiiciently to cause said sealing means to cover said hole.

References Cited in the file of this patent UNITED STATES PATENTS 2,026,196 Stephens Dec. 31, 1935 2,647,939 Palucv Aug. 4J 1953 FOREIGN PATENTS 575,058 Great Britain Feb. 1, 1946 565,677 Canada Nov. 4, 1958

Claims (1)

1. A BUSHING OF THE TYPE THAT EXTENDS IN SEALING RELATIONSHIP THROUGH THE WALL OF A TANK CONTAINING ELECTRICAL APPARATUS IMMERSED IN A DIELECTRIC LIQUID, COMPRISING, A HOLLOW EXTERIOR EXTENSION MOUNTABLE OUTSIDE THE TANK, A HOLLOW INTERIOR EXTENSION MOUNTABLE INSIDE THE TANK, SAID INTERIOR EXTENSION HAVING AN INWARDLY TAPERING SURFACE, SAID SURFACE HAVING A HOLE CONNECTING THE INTERIOR OF THE BUSHING TO RECEIVE DIELECTRIC LIQUID FROM THE TANK, A CONDUCTOR EXTENDING THROUGH SAID BUSHING EXTENSIONS IN AN AXIALLY SLIDABLE RELATIONSHIP, SEALING MEANS AXIALLY MOVABLE WITHIN SAID INTERIOR EXTENSION BETWEEN AN INWARD POSITION AND AN OUTWARD POSITION, SAID SEALING MEANS COMPRISING A HOLLOW SLEEVE HAVING AN OUTER SURFACE AND A HOLE ON SAID SURFACE FOR ADMITTING THE LIQUID; SAID OUTER SURFACE BEING SHAPED TO BE PARALLEL TO SAID INNER SURFACE AND TO BE SPACED FROM SAID INNER SURFACE WHEN SAID SLEEVE IS IN SAID OUTWARD POSITION AND TO ABUT SAID INNER SURFACE TO CLOSE THE INTERIOR OF SAID BUSHING FROM SAID TANK WHEN SAID SLEEVE IS IN ITS RELATIVELY INWARD POSITION, MEANS ON SAID CONDUCTOR FOR ENGAGING SAID SEALING MEANS WHEREBY SAID SEALING MEANS IS POSITIONABLE ACCORDING TO THE AXIAL POSITION OF SAID CONDUCTOR, BIAS MEANS MOUNTED BETWEEN SAID INTERIOR EXTENSION AND SAID SEALING MEANS TO URGE SAID SEALING MEANS INWARDLY, AND EXTERIORLY ACCESSIBLE MEANS FOR FASTENING THE OUTER END OF SAID CONDUCTOR TO SAID EXTERIOR EXTENSION, SAID MEANS BEING OPERABLE DURING UNFASTENING TO RELEASE SAID CONDUCTOR TO MOVE INWARDLY WHEREBY SAID BIAS MEANS POSITIONS SAID SEALING MEANS TO SEAL THE INTERIOR OF SAID BUSHING FROM SAID TANK, SAID MEANS BEING OPERABLE DURING FASTENING TO MOVE SAID CONDUCTOR OUTWARDLY WHEREBY SAID SEALING MEANS IS POSITIONED TO ADMIT LIQUID FROM SAID TANK TO SAID BUSHING INTERIOR.

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