US2630470A - Capacitator terminal bushing with auxiliary sealing ring - Google Patents

Description

March 3, 1953 D. E. GRAY 2,330,470

` CAPACITATOR TERMINAL vRUSHING W'ITH AUXILIARY SEALING RINGp Filed Feb. 17, 19218 flrwmmf.

Patented Mar. 3, 1953 CAPACITATOR TERMINAL BUSHING WITH AUXILIARY SEALING RING Donald E. Gray, Teaneck, N. J., assignor to Cornell-Dubilier Electric Corporation, S'outh Plainfield, N. J., a corporation of Delaware Application February 17, 1948, Serial No. 8,791

1 Claim.

This invention relates to improved terminal constructions particularly adapted to be mounted on a closure or other portion of a container for an electrical capacitor. The terminals herein referred to are composed in large part of ceramic, such as porcelain, steatite or the like, usually having, as in common practice, a glazed outer surface. Such terminals are fashioned to contain a liquid or semi-liquid dielectric such as mineral oil, chlorinated diphenyl or other oils or compounds. In operation, therefore, the terminal functions as a connecting point for an electrical circuit, as a seal for an aperture in the capacitor container and also as a container for the liquid or semi-liquid dielectric which is contained within the terminal. Rigorous and testing conditions, such as are encountered in tropical climates and along seacoasts, often give rise to failures in such terminals or to partial failures which cause inefficient performance. Such failures result because of difficulties encountered in sealing the various parts of the terminals to each other and to the container in which they are mounted. If the seals used are subject to deterioration because of climatic conditions or bei.

cause of physical shocks, air or moisture may enter the capacitor enclosure or the liquid dielectric contained in the terminal may leak therefrom.

The general object of this invention is to pro- Vide an improved termina] construction particularly adapted to withstand rigorous service conditions. A specific object is to provide a sealed terminal structure which, at important joints, is provided with a protective double seal designed to give long and efficient life to the terminal and to the capacitor assembly of which the terminal is a part.

Fig. 1 of the accompanying drawing is a side elevational view, partly in section, of a terminal constructed in accordance with this invention.

Fig. 2 is a partial view of the terminal shown in Fig. 1 and illustrates one modification which may be made in said terminal.

Referring to Fig. l, the terminal is shown in position on a cover I of a steel capacitor container II. It will be realized that whether the terminal be seated on the cover or on another wall of the container I I is unimportant. Usually, however, the terminal is seated on the cover to facilitate assembly. In the nal assembly of the capacitor the cover I0 is welded or otherwise permanently affixed to the can i I. The terminal parts include the ceramic outer bushing I2, the ceramic inner bushing I3 and the metallic connector cap I4, provided with means I5 for con nection to an electrical circuit. The bushing I2 is shaped to provide an inner cavity in which is contained a liquid dielectric medium I6. The terminal parts are held in assembled relation by the stud I'I, one end of which threads into the cap I4 and the other end of which is aiiiXed tc a holding disc I8. Connection of the stud I'I to the capacitor elements is conventional and is not shown. Since various types of capacitor bodies may be used with terminals, the capacitor elements which are placed within container II are not shown. After the porcelain bushings I2, I3 and the cap I4 have been assembled, as shown, on the cover I0 the dielectric I6 is introduced, through a hole I9 in the cap I4 and thence through a corresponding channel 20, drilled in stud l'I, into the sealed chamber formed by the terminal assembly. Thereafter the hole I9 is sealed as, for instance, by a solder cap 2l.

Attention is now directed to the two joints in this terminal assembly which are exposed in the sense that they lie entirely or partially outside of the container I I. The upper joint is between the metallic cap I4 and the upper end of the ceramic bushing I2. It will be noted that if the capacitor be maintained upright as shown, failure of this joint will not allow leakage but will allow possible contamination, by atmosphere or moisture, of the contents of the terminal (but not of the contents of the container II). The lower joint is, in eifect, between the ceramic bushings I2 and I3 andthe cover I0. Failure of this joint would allow drainage of the liquid dielectric I5 and also contamination of the contents of container II by atmosphere or moisture. Further, it will be noted that stresses applied to the ter minal assembly during use tend to concentrate in this lower joint.

As a step in the assembly of the terminal shown in Fig. 1, the outer ceramic bushing I2 is provided, over the surface areas generally indicated by brackets 22 and 23, with a thin metal coating, such as platinum or silver. If desired, these metal coated areas may be tinned or coated with another metal receptive to a selected solder. Prior to assembly there is also provided a rela tively thin metal cap washer 24 perforated to loosely admit stud I'I. To prevent unnecessary corrosion hazards, it is advisable to form cap washer 24 from metal which is the same as that used to make connector cap I4, usually copper. However, parts I4 and 24 may be formed of different materials, if desired. It is preferred, but not necessary, to weld, solder or otherwise assemble cap washer 24 to cap i4 prior to final assembly of the terminal.

As the parts of the terminal are assembled on cover it in the position shown, resilient sealing means, such as gaskets 25, 29 and 2l are proe vided. These gaskets are preferably made of cork or other resilient material of good body, and just prior to insertion into the assembly are preferably painted or sprayed with a cement, such as a resin varnish, thereby insuring that the gaskets will be firmly sealed to adjoining parts; viz., as to gasket 25, the bushing l2 and the cover I; as to gasket 2li, the bushing I3 and the cover I9, and as the gasket 27, the bushing I3 and the metal disc I8.

After assembly is complete and the stud Il", the cap I4 and the disc I8 have been adjusted to tightly hold the terminal parts together and to compress the resilient members 25, 2S and 2l to form a leak proof seal, the depending edge of cap washer 24 is soldered to the surface oi thev bushing I2. The solder band 28 thus formed is built up upon the metallized surface which, as above described, had been originally furnished on the outer surface of the bushing. Thereafter, or previous thereto (the sequence being of no signiiicance to this invention) an impervious member, such as metal ring 29, is soldered or otherwise ixed to the previously inetallized wall of bushing l2, as indicated by the solder band Sii. The depending edge of ring 29 is soldered to the cover lll, as indicated by the solder band 3l. To facilitate soldering of the depending edge of ring 29 to the cover l0, it is preferred to emboss the cover with the depression 32 and to so proportion ring 29 that the depending edge thereof extends into the depression 32 as shown.

. The thus constructed terminal is in effect sealed to the container II with a resilient double seal which has great eiiciency and tightness under the most adverse conditions of use. The outer sealing ring 29 forms not only a complete seal but likewise a protective metal cover which protects the resilient gasket 25 against atmosphere, moisture and other agents or forces which in use may tend to age the resilient material and thereby shorten its life as a sealing medium. Moreover, if the resilient gasket 25 should fail for any reason, a not unusual reason being the aging effects of tropical temperatures or the effects of eXtreme cold, thus allowing leakage of the dielectric medium i6, the medium will not escape but will ll the area 33 between ring 22 and cover IG and bushing l2, thereby forming an additional seal against contamination oi the contents of container H by minute. quantities of gaseous contaminants which may pass through any porosity present in solder bands 3@ and 3i.

The seal provided by the cap washer 2t at the top of bushing I2 is particularly effective because it is built entirely of metal and any uneven seating of the top of bushing i2 against cap washer Eil as would tend to allow leakage of gaseous or liquid materials into the dielectric chamber is eiectively counteracted by the soldered down depending edge of the cap washer which forms, in elect, a protective hood. However, this joint may, if desired, be constructed in various other ways with good results, one convenient construction being shown in Fig. 2. In that construction, which is otherwise similar to the terminal shown in Fig. 1, the connecting cap 28 is fashioned with a depending rim 34 to form a seat for a resilient gasket 35. When, upon manipulation of stud 31, the parts are pulled firmly together and the gasket 35 pressed against the upper surface of bushing Sii, the edges of the gasket are protected by the depending rim 34.

It will be understood that shapes of the parts shown in the various gures and the materials of which they are made may vary without departure from the principles of this invention, except as indicated in the appended claim.

Having thus described my invention, I claim:

A capacitor element comprising in assembled relation a capacitor wall having a terminal as- .sembly receiving aperture therein and a terminal assembly extending through and sealing said aperture, said terminal assembly including an inner ceramic bushing seated under said aperture and having a surface thereof disposed adjacent to and substantially parallel with the inner surface of said wall, a irst resilient sealing member seated between and in sealing contact with the adjacent substantially parallel surfaces of said inner bushing and the inner surface of said wall, an outer ceramic bushing shaped to denne with said inner bushing a liquid containable dielectric chamber, said outer bushing being seated over said aperture and bearing upon a second resilient sealing member seated between and in sealing contactl with the substantially parallel surfaces of said outer bushing and the outer surface of said wall, a sealing cap seated upon the upper extremity of said outer bushing, a cap washer disposed between said sealing cap and said outer bushing and having a dependent peripheral flange portion extending downwardly ver a portion of the surface of said outer bushn ing and ilxed thereto in hermetic sealing relation, means, including a circuit connecting member. positioned to maintain said terminal parts in assembled sealing relationship with the wall of the container and an exposed metal auxiliary sealing member disposed around a lower portion of the peripheral surface oi the outer bushing and extending downwardly to the container wall, said member being xed to said peripheral surface in hermetic sealing relationship, and fixed to said container wall in hermetic sealing relationship at a location remote from the terminal aperture therein to form a sealed space surrounding the sealing engagement between said bushings, said wall and the resilient members interposed therebetween.

DONALD E. GRAY.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,894,993 Jansson Jan. 24., 1933 1,910,226 Austin May 23, 1933 1,983,335 Austin Dec. 4, 1934 2,292,031 Arnold Aug. 4, 1942 2,326,152 Marbury Aug. 10, 1943 2,411,656 Henderson et al Nov. 26, 1946 2,434,554 Fields Jan. 13, 1948 2,499,769 Middleton, Jr. Mar. 7, 1950 2,598,184 Morisuye et al May 16, 1950 FOREIGN PATENTS Number Country Date 914,120 France June ll, 1946

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