US2356831A

US2356831A - Leakproof terminal structure

Info

Publication number: US2356831A
Application number: US462698A
Authority: US
Inventors: Monte Robert W De; Louis E Milarta
Original assignee: Bell Telephone Laboratories Inc
Current assignee: AT&T Corp
Priority date: 1942-10-20
Filing date: 1942-10-20
Publication date: 1944-08-29
Anticipated expiration: 1961-08-29

Description

Aug. 29,1944, R. W. DE MONTE ETAL 'LEAK-PROOF TERMINAL STRUCTURE Filed Oct. 20, 1942 R ne 05 MONTE Patented Aug. 29, 1944 2,356,831 mmaoor TERMINAL srancrrmn Robert W. De Monte. Glen Ridge, N. J., and Louis E. Milarta, Hollis, N. Y., assiznors to Bel] Telephone Laboratorles, Incorporated, New York, N. Y., a corporation of New York Application October 20, 1942, Serlal No. 462,698

1 Claim.

This invention relates to an electrical terminal and}; method of constructing and mounting the terminal on an apertured wall.

The object of the invention is to provide 9. terminal structure and arrangement suitable for use on a casing which must be seaied against the outrance of moisture or the escape of oil or other filling material in the casing.

The terminal when constructed and assembled according to the invention will be suitable for use, for instance, on transformer casings even when thecasing is subjected to various moisture conditions containing salt and when the casing is subjected to Wide ranges of temperature changes. The construction and arrangement may also be used on oil-fllled casings and terminais mounted thereon.

In the drawing the single figure shown thereln is a view partly in section of a portion of a casing and the terminal mounted on and extending through an apertured wall in the casing. It will be understood that the casing may contain a transformer or some other electrical apparatus (not shown) The casing 2 may be of any desired shape or form but is shown merely for the purpose et illustrating the invention as comprising 8. cuplike body 3 and a. cover 4 which serves as a top closure Ior the upper end of the body 3. The cover 4 is secured to the body 3 in any suitable marmot to provide a leaf-prooi Joint between the casinz parts. The body 3 and the cover 4 may -be made, for instance, et sheet metal and the body and cover may be welded or soldered tozether as shown at 5 to provide a leak-prooi Joint betWee1ithe parts. The cover 4 is apertured' gitudinally through an insulating bushing Il which extends through the aperture I in the cover 4. The conducting rod n la male-threaded on its lower and l2 to receive a nut II and in provided with an integral fiance I4 near its upper end II. The bushing Il is made of ceramic'material and has a frusto-conical upper portion I! portion [6 s 01. larger diameter than the aperture S. A cylindricai tubular portion 11 of the insulating bushing Il extends through the aperture 6 and for a considerable distance below the cover 4, the portion H being of slightly smaller outside diameter than the aperture 6. A tubular collar 18 of ceramic material is telescoped over the lower end of the portion Il.

Insulating washers MI, 20, 2l, 22 and 23 are provided in the terminal 1 to partly seal parts of the structure pressed into engagement with other Parts when the terminal 1 is assembled and mounted on the cover 4. The washers l9, 20, 2l, 22 and 23 are made of flbrous insulating material and are somewhat compressea when the terminal 1 is assembled and mounted in place. Hempwood pulp has been found to be a suitable materiall for the washers above mentioned. We do not desire to be limited to the use of this particular materlal, however, since other fibrous insultting materials are in some cases found suitable for the purpose. The washer l9 is placed on the conducting rod H) and so that it is disposed betweenthe flange I4 and the top oi the insulating bushing II. The washer 20 is placed on the portion I! of the insulating bushing H and so that it: is disposed between the lower and of the trusto-conical portion l6 and the upper surface oi! the cover 4. The washers 2l, 22 and 23 are placed on the portion ll of the insulating bushing il in the order named and so that they are located between the upper and of the collar Il and the undersuriace of the cover 4. The washer 2l 15 nearest to the cover 4. A pile-up of washers 24, 2l, 26 and a look washer 21 all made oi conducting material are placed in the order named on the. conducting rod Il! and are held thereon by means 01 the nut in. The washer 24 is et larxer diameter than the inside diameter of the collar Il and is disposed against the lower end 01 the collar la. When the nut H 1s tightened on the rod I, the parts of the terminal 1 are drawn into closely assembled condition and the washers II, 20, 21, 22 and 28 are somcwhat compressed. The washer 25 is provided with an angularly disposed apertured ear portion 28 so that a conductor wire (not shown) may be electrically connected to the terminal 1. The conductor wire mentloned niay form an electrical connectlon between the terminal 1 and an electrical device located in the casing 2.

In assembfing the terminal 1 above described and in mountinx the terminal on the casing 2 a particular technique is Io1lowed and a moisturelocated above the cover 4 and the base of the proot sealinz compound 20 is applied to certain of the parts make the structures leak-proof at certain points where parts of the terminal are pressed together and where the terminal extends through the cover 4. The technique above mentioned is as follows:

(1) The coatings 8 and 9 on the cover 4 are abraded or rubbed down to form seating surfaces for the washers 20 and H, the seating surfaces being formed only in the coatings I and 9. The seating surfaces should not contain grooves extending radiaily of the aperture and may be formed by circularly rubbing or machining the coatings 8 and 9 around the aperture in the casing. The seating surfaces formed are cleaned with carbon trachloride or other suitable cleaning fiuid and then thoroughly dried.

(2) The under surface of the flange M and immediately adjacent portion of the conducting rod l0. the top and the lower surface of the frustoconical portion Hi of the insulating bushing Il are cleaned with carbnn tetrachloride or other suitable cleaning fluid and then thoroughly dried.

(3) The washers IS, 20 and 2l are cleaned with a suitable claning fluid. These parts are evendried at a temperature of 140 F. to 160 F. for about four hurs. The washers la, 20 and 2l should then be stored in a desiccator or equivalent containing calcium chloride until required for ass mbling in the terminal when they should be removed and handled with tweezers or other pick-up tool to insure cleanliness of the washers until applied in the terminal assembly.

(4:) A coat of moisture-proof seaiing compound 28 is applied to the seats formed in,the coatings I and 8 on the cover 4, the sealing compound beinz of such character that it will balte to substantiaily permanent hardness when subjected to a temperature of between 220 F. and 240 F. for twelve to sixteen hours.

(5) A coat of the above-mentioned sealing compound is applied to the under surface of the flange H and the immediately adjacent portion of the conducting rod III.

(6) A coat of the sea1ing compound is applied to the top and lower part of the frusto-conicai portion IS et the insulating bushing il.

(7) The washers IS, and M are dipped in the sealine compound and assembled in the terminal 1 in condition for clamping the parts together by operation 01 the nut l3, the parts coated with the seaiing compound being assembled while the seaiing compound is in a tacky condition.

(8) While the sealing compound is in a tackv condition the nut li on the rod I0 is tightened to hold the parts in tightly assembled condition.

(9) The terminal 1 and the cover 4 are baked at a temperature of between 220 F. and 240 F. for from fourteen to sixteen hours.

(10) The nut Il is still further tightened on the rod Il) while the parts are still at about the temperature above mentioned.

(11) A coat of the sea1lng compound is applied to the outer edge of the fiange l4, the outer surface of the washer I! and the outer surface of the upper part of the portion IS et the insulating bushing l l.

(12) A coat of the sealing compound is applied to the outer edze of the washer 20 and so that the coat of sealing compound extends over the outside of the lower part f the portion I6 and also over the nearby portions of the top surface of the cover l.

(13) A coat of the sealing compound is applied to the outer edge of the washer 2l and so that the coat of seaiing compound extends aiso over the nearby portions of the lower surface of the cover 4.

(14) The cover I and the terminal 1 mounted thereon are then baked at a temperature between 220 F. and 240 F. forabot twelve hours.

We have found that when a terminal is constructed as above described and is mounted on a casing as shown in the drawing, and the aboveoutlined technique is followed in preparing and assembling the parts, the construction is leakproof and will remain leak-proof even when the casing and terminal are subjected to relatively high and low temperatures or when the casing and terminal are immersed in sait water and the temperature of the water is changed over a relatively wide range. The sealing compound employed in making the structure and arrangement leak-proof must obviously be of such character that it wiil not crack or fail to perform its seaiing function under the conditions met in service. A relatively high-temperature baking enamel may be used as the sealing compound. A seaiing compound we have found to be satisfactory for the purpose is a mixture or a high-temperature baking enamel and toluol in the proportions of 3.5 to 4 parts by volume of enamel to one part of toluol.

What is claimed is:

A leak-proof terminal structure and arrangement coinprising in combination, an apertured wall coated on opposite faces with relatively soft metal, seats formed in the coatings on said wall around the aperture in said wall, washers disposed on opposite sides of said wall and resting in said seats, an insulating bushing, an enlarged upper portion on said bushing eXtendin above said washers. a reduced lower portion on said bushing extending through said wall and said washers, a conducting rod extending longitudinally through said bushing, a flange on said rod extending over the upper portion of said bushing, a washer located between said flange and the top of said enlarged upper portion Of said bushing, a collar supported on the lower portion of said bushing, mans on said rod to hold the terminal parts in tlghtly assembled condition and press the washers in said seats against said seats, coats of moisture-proof seaiing compound covering the washers in said seats and extending into leakproof seaiing engagement with said wall and a coat of leak-proof sealing compound covering the washer on the upper end of said bushing and extending into leak-proof sealing engagement with said bushinz and said flange.

ROBERT W. DE MONTE. LOUIS E. MILARTA.