US2456640A

US2456640A - Electrical apparatus bushing

Info

Publication number: US2456640A
Application number: US554100A
Authority: US
Inventors: Leonard J Linde; Nicholas F Arone; Benjamin E Spiro
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1944-09-14
Filing date: 1944-09-14
Publication date: 1948-12-21
Anticipated expiration: 1965-12-21

Description

Dec.

L. J. LINDE ETAL ELECTRICAL APPARATUS BUSHING Filed Spt. 14, 1944 [fivenbors Leonard J. Linde Nicholas P. Aroma,-

BenJ amin E. Spiro Their Abtovne Patented Dec. 21, 1948 ELECTRICAL APPARATUS BUS KING Leonard J. Linde, Drexel Hill, Nicholas F. Arone,

Upper Darby, and Benjamin E. Spiro, Philadelphia, Pa., assignors to General Electric Com- Y pany, a corporation of New York Application September 14, 1944, Serial No. 554,100

' 5 Claims. (Cl. 174-152) Our invention relates to electrical apparatus, such as circuit breakers or the like, wherein an insulated electrical conductor generally referred to as a bushing extends through a wall or cover of an electrical housing or the like. Specifically our invention is concerned with a new and improved electric bushing for electric circuit breakers or the like. I

Bushings for electric circuit breakers, of the type particularly adapted for use with metal-clad switchgear, have been constructed by placing a conductor within a treated paper or fabric insulated tube. This insulated tube then was machined along a part of its length from one end thereof to produce a body portion of reduced cross section after which a fianged metal supporting cylinder was pressed over this reduced body portion. Finally an insulating sleeve for backing up the supporting cylinder was pressed over the remaining portion of reduced cross section. This cult breaker which happens to be particularly adapted for use in metal-clad switchgear. This circuit breaker is in many respects similar to the circuit breaker disclosed and claimed in Linde Patent 2,293,513, granted August 18, 1942, and assigned to the same assignee as the present applicatl0n.. such a breaker comprises a plurality of conductor studs or bushings such as I and 2, each'provided with a'suitable mounting flange so that the conductor stud or bushing may be supported where it passes through the wall or housing 3 of the circuit breaker, generally indicated construction required the close fitting together of the long machined surfaces of the several component cylindrical members, otherwise breakdown often resulted when high voltage impulses were applied.

Our inventionis particularly concerned with providing a new and improved bushing for electric circuit breakers or the like and which, because the support therefor is fabricated, is simpler and less dependent upon the close fits of its component parts, and which arrangement results in a more satisfactory bushing.

It therefore is an object of our invention-to provide an improved apparatus of this character, which apparatus shall be simple in construction, effective in use and inexpensive to manufacture.

Further objects and advantages of our invention will become apparent as the following description proceeds and the features of novelty which characterize our invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of our invention reference may be had to the-accompanying drawing in which Fig. 1 'isan elevationalview partly in section of an electric circuit breaker employing bushings embodying our invention; Figs. 2a, 2b, 2c, 2d and 2e illustrate successive steps in manufacturing the bushing embodying our invention; Fig. 3 is a sectional view taken on line i=4 of Fig. 2e, and Fig. 4 is a view similar to Fig. 2e illustrating a modified bushing made in accordance with our invention. 7

Referring now to Fig. 1, we have illustrated our invention as applied to a well known form of cirat 4. The bushing I in the case of a breaker such as is disclosed in the Linde patent, is somewhat shorter than the bushing 2. We have illustrated the complete bushing i in Fig. 2e and the complete bushing 2 inFig. 4.

The bushing I includes. an axial conducting stud or core member 6 formed of copper or the like,

having a spherical plug type terminal 8 formed at one end thereof for engaging self-aligningiy with a cooperating resilient socket type terminal. The end of conductor 5 opposite from terminal 6 is provided with a suitable configuration I, so as to be adapted for connection to a contact such as the stationary contact of the circuit breaker 4. Except for the terminal 8 and the rectangularly configured portion 1, conductor 5 preferably comprises a cylindrical rod,

In order to insulate conductor 5 from the grounded portions of the circuit breaker 4 including the housing 3, the conductor 5 is first pressed into a cylinder or tube 8 of insulating material, the tube 8 being slipped over the end 6 of conductor 5 after an end thrust washer I has been placed upon the rod 5 for abutting the end portion 1 as'indicated in Fig. 2a. Preferably this cylinder is constructed of laminated sheet organic material united by an adhesive binder. A portion of the cylinder 8 intermediate the ends thereof is undercut bymachining so as to form a portion of reduced circular cross section 9. This step is preferably performed after the cylinder 8 is pressed around conductor 5. Fig. 2a illustrates the bushing after the machining operation on cylinder 8 is performed.

In Fig. 2b there is shown a perspective view of a pair of fianged semi-cylindrical metal members Ill and II which are constructed so as to fit around the portion of reduced cross section 9 and completely envelop the same. The flanges I2 associated with the members It and II provide the means for supporting the conductor stud at the point where it passes through the wall or housing 3 of circuit breaker 4. The ends of the semi-cylindrical members I and ii.

semi-cylindrical members ill and Ii preferably are tapered as indicated at It so that when they are applied to the insulating cylinder 8 they underlie the surface of the cylinder 8, thereby raising the corona point in this region of high electrlcal'stress to a safe value thereby permitting the improved bushing constructed according to our invention to withstand the desired impulse voltages.

The next step'in the process of constructing the bushing or conductor stud of our invention comprises cementing the semi-cylindrical flanged metal members i and II to the portion of reduced cross section 9 of cylinder 8. We have found that a phenolic modified polyvinyl butyral resin cement is very satisfactory for this purpose. This cement is applied to the holding surfaces and the semi-cylindrical members ill and II then are clamped with pressure about the cylinder 8 and baked for approximately an hour at 250 C. in order to set the cement. The bushing or conductor stud with the flanged semi-cylindrical members cemented thereto is afterwards placed in a lathe to true up the cylindrical surfaces of the flanged members ll and if as well as to insure that the mounting surfaces of the flanges I! are perpendicular to the axis of the bushing. At the same time, an annular groove i4 is machined into the semi-cylindrical members, as is clearly indicated in Fig. 2c. The conductor stud or bushing disclosed in Fig. 2c illustrates the appearance thereof after the above steps in the process of manufacture have been performed.

In Fig. 2d there is illustrated a perspective view of a thin-walled metal tube i5, preferably formed of brass or the like, having an inside diameter such that it is readily slidable over the cylinder I and the trued curved surfaces of the cemented halves Ill and ii. A small hole I6 is provided in one of the semi-cylindrical flanged members, as is clearly indicated in Fig. 3. The thin-walled metal cylinder i5 now is, slid over the terminal end 6 of the conductor 5 to surround the semi-cylindrical members I 0 and il above the flanges i2. To prevent this tube i5 from rotating, a portion of the tube indicated at H in Figs. 2c and 3 is indented into the hole I 8 in the semi-cylindrical member i ll. Thereafter the cylindrical tube or sleeve i5 is deformed by spinning it, as indicated at it, into the annular groove l4 thereby producing a tightly gripping retaining ring which reinforces the cemented The now completed bushing, as indicated in Fig. 2c, is ready for installation in the circuit breaker I and for which purpose suitable mountin bolts are used which extend through the openings I9 in flanges i2 and through corresponding holes in the breaker housing 3.

In Fig. 4 we have illustrated the conductor stud or bushing 2 which is constructed in a manner very similar to the bushing i described above, except that the undercut portion of the insulating tube is somewhat longer and consequently the semi-cylindrical members are correspondingly longer. The conductor stud or bushing 2 also comprises a conducting rod having a spherical plug type terminal at one end thereof and a suitable rectangularly configured portion 2| at the other end, which may be adapted so as to support the pivoted contact of the above-mentioned type electric circuit breaker. A thrust washer 22 is slipped over the terminal end 20 of the conducting member until it engages the portion 1|, after which the insulating tube 23 is slipped over the terminal 20 and pressed into position. .As in bushing I, the portion of reduced cross section 24 intermediate the ends of the insulating tube 23 preferably is machined after the tube is assembled on the conducting member. The flanged semi-cylindrical members such as 25, only one of which is shown in Fig. 4 since the other is hidden from view, are then cemented to the portion of reduced cross section 24 after which these sembcylindrical members are trued up in a lathe and the flanges 28 associated with the semi-cylindrical members 25 are machined on their mounting face so as to be truly perpendicular with the axis of the bushing. Also two annular grooves similar to the annular groove ll of Fig. 2c are cut in the semi-cylindrical members, one above and one below the flanges 28. A clamping sleeve 21 substantially identical with clamping sleeve i5 is slipped over the terminal end II of the bushing 2 and held from rotatin by an indentation 28 while the sleeve is deformed, as by spinning into the annular groove indicated at 29. Similarly a sleeve 30 is slipped over the other end of bushing 2 so as to clamp the lower ends of the semi-cylindrical members such as 25. The clamping sleeve 30 is also prevented from rotating by indenting a portion thereof as indicated at 3i into an opening formed in one of the semi-cylindrical members 25 after which the clamping sleeve 30 is deformed by spinning it into the associated annular groove, as indicated at 32.

It will be obvious that the above-described cementing method used in the manufacturing process of the bushing 01' our invention produces an exceedingly strong adhesive Joint between the cylinder of insulatin material and each curved portion of the flanged supporting members in order for these Joints to withstand the strain from the subsequent intermediate machining, grooving and spinning operations as already described. Actually, we have found these cemented Joints to be adequate for supporting the bushing through the agency of its composite flanged cylindrical supporting structure without benefit of any further reinforcement; so that the spun sleeves i5, 27 and 32 may be regarded rather as providin additional security for the flanged halves and also for imparting an appearance of solidarity to the finished product.

It will be appreciated from the above explanation that we have provided new and improved electric bushings which are simple to manufacture in that they eliminate the requirement of close flts which are difllcult to maintain and which necessitates accurate and long machined surfaces. In addition the tapered portions ll of the semi-cylindrical members in and Ii are effective in raising the corona point to a safe value whereby the bushings 0r conductor studs 01 our invention withstand higher impulse voltages than in comparable bushings as constructed heretofore.

Although we have disclosed particular embodiments of our invention, it will be obvious to those skilled in the art that modifications may be made without departing from our invention and we intend in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States, is:

1. A terminal bushing for an electric switch comprising a conducting member including a terminal formed thereon, an insulating sleeve having a reduced mediate the ends thereof enclosing a substantial "portion of said segmental members so as tightl said portion oil reduced cross section, and a thin walled metal tube surrounding said semi'-cylin-' drical members so as tightly to grip said members to reinforce the same. a

2. A bushing for an electric switch comprisin a conducting member, an insulating sleeve enclosing a substantial portion of said conducting member, supporting means encircling said sleeve including a pair of flanged semi-cylindrical members cemented to said sleeve, and a thin walled metal tube surrounding said semi-cylindrical members so as tightly to grip said members to reinforce the same.

3. A bushing for an electric switch comprising aconducting member, an insulating sleeve having a reduced cross section portion intermediate the ends thereof enclosing a substantial portion of said conducting member, supporting means encircling said sleeve including a pair of flanged semi-cylindrical members cemented to said portion of reduced cross section. a thinwalled metal tube surrounding said semi-cylindrical members, and means for causing said tube tightly to grip and reinforce said semi-cylindrical members comprising an annular groove in said semicylindrlcal members and a cooperating deformed portion on said metal tube.

4.-A bushing for electric apparatus comprising a central rod-like conducting core, an insulating cylindrical sleeve completely surrounding part of the length .of said core, supporting means comprising a plurality of segmental component members arrayed circumferentially around a portion of said sleeve, each said'member including a curved portion conforming to the curvature of said sleeve, cementing material interposed between said segmental members and said sleeve to form a bond therebetween, and a thin walled metal tube surrounding the curved to grip said members to provide reinforcement for the bond between said segmental members and said sleeve.

5. A bushing for electric apparatus comprising a central rod-like conducting core, an insulating i cylindrical sleeve completely surrounding part of the length of said core, an annular recess around said sleeve, supporting means comprising a plurality of segmental component members arrayed circumferentially around said annular recess, each said member including a curved portion conforming to the curvature of said annular recess, cementing material interposed between said segmental members and said sleeve to form a bond therebetween and an in- V dented metal tube surrounding the curved por-.

tion of said segmental members so as tightly to grip said members to provide reinforcement for the bond between said segmental members and said sleeve.

LEONARD J. Iii-Non;

NICHOLAS r. ARONE.

BENJAMIN n BPIRO.

REEERENoEs crrEn The following references are of record in the file of this patent: