US2230194A - Bushing - Google Patents

Description

Jan 28, 1941- L. J. STEVENS 2,230,194

BUSHING sept. 6'

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Patented Jan. 28, 1941 UNITED STATES BUSHING Leland J. Stevens, Baltimore, Md., assignor to Locke Insulator Corporation, Baltimore, Md., a

corporation of Maryland Applicatin september s, 1939, serial No. 293,649

4 Claims.

The invention relates to bushings and more particularly to mean for connecting thereto metallic caps and/or connectors generally used with bushings for transformers and the like.

'I'he principal object of the invention, generally stated, is to provide a bushing cap which may be so connected to a bushing as to provide a fluid and gas tight'joint therebetween, said joint serving to prevent leakage from or into said bushing.

Another object of the invention is to provide a simple form of bushing which may be connected to the electrical vapparatus for which it is designed in any one of a number of ways and which is provided with a cap sealing the interior ,of said bushing, said cap having formed therein an opening, the side edges of which are adapted to cooperate with the electrical connector for maintaining the same against rotation with respect of both cap and bushing.

A still further object of the invention is to provide a simple, strong and inexpensive means for rigidly and permanently securing a. metallic cap to a bushing, said means being adapted to prevent relative rotation between the cap and bushing.

wOther objects of the invention will appear from the detailed description thereof, especially when taken in connection with the accompanying drawing in which,

Figure 1 is an elevational view partially in section, illustrating a bushing and means for clamping the same to the transformer or other electrical apparatus,

Figure 2 is a top plan view of the structure shown in Figure 1.

Figure 3 is a central vertical section of Figure l.

Throughout the specification and drawings like parts are designated by like reference characters.

Before describing the preferred embodiment of the invention which I have illustrated, it is believed it will lead to a better understanding of the invention to describe the general conditions now existing in this particular branch of the electrical art.

Manufacturers of electrical apparatus such as transformers using entrance or lead-in bushings generally provide their own characteristic means for connecting the bushing to the apparatus. 'I'his practice necessitates the bushing manufacturers providing a large number of alternate styles of bushings so as to provide a bushing which will cooperate with the dierent types of fastening or securing means utilized by the bushing manufacturers. The result has been that the bushing manufacturers are required to keep in stock various styles of bushings or to keep in stock molds from which these bushings of different styles may be manufactured. It has been found, however, that by changing the external shape of the bushing to the form illustrated in the accompanying drawing it is possible to use a single style of bushing with a number of different makes of transformers.

The problem outlined above is only one of the problems which the insulator or bushing manufacturer has to face in connection with the production of these bushings. It is of course essential that the connection between the line conductor and the lead-in conductor or electrical connector be rigidly maintained in respect of the bushing and its cap and that the connection between the line conductor and/or the electrical connector carried by the bushing be maintained against rotation in respect of the bushing at the time of connection and during the subsequent use of the apparatus. It has therefore been customary either to counter-bore the bushing and/or to provide the same with a key-way so that the metallic connector, when inserted in the bushing, would cooperate with the shaped portion of the recess or the key-Way so as to be maintained against rotation with respect of the bushing. It is exceedingly diflicult and expensive to counterbore or to cut key-ways in the clay since these operations can be performed only after the clay has arrived at either the leather or bone dry Astate and such manipulation of clay in the leather or bone dry state is apt to cause incipient cracks which do not show until after the piece has been finished or fired.

Referring now to the embodiment of the invention, the numeral i designates generally a lead-in or entrance bushing adapted to be rigidly connected to a portion of the housing 2 of a transformer or other electrical apparatus 3. This type of bushing is preferably produced by the extrusion process, the clay from the pug mill being forced through the nozzle of the pug mill and formed into a hollow column or pipe, the maximum diameter of which is slightly greater than the maximum diameter of the finished bushing measured over the petticoat I. After the clay has been formed as a hollow column and allowed to dry it is placed in a lathe or other machine and the petticoats 4. 5, 6 and l, as well as the ange 8 and the head 9, are turned thereon. It'will be understood that the number of petticoats may be altered as desired and that if desired the opposite end of the bushing may PR 21 i942 IEISSUED also be formed with a head similar to the head 9. The fiange 8 is undercut, as' at III, to form a downwardly facing recess I I into which a washer I2 is adapted to nt, the washer in turn resting, when the parts are in assembled position, upon a flange I3 formed around the opening I4 in the transformer housing. I have illustrated the bushing as being connected to the transformer by a plurality of J clips I5, each of which is provided in the leg I6 .with an opening I1 through which the bolt I8 is adapted to. project. The other leg' I9 if each clip is provided with a notch 20 adapted to embrace the adjacent side ofthe bolt I8, the 4leg `I6 of the clip being adapted to overlie theange Band'theclips are maintained in `tighty engagement with the ange by means of the-nuts 2| vwhich are screw-threadedly connected to the bolts i8.. It will thus be seen that by applying pressure to the clips `I5 the washer or ga'sket I2 is forced into tight and intimate contact with the flange 8 of the bushing and flange I3 of'th'e'transformer housing forming a leak-proof connection between the bushing and the transformer,

The head 9 is provided at its lower portion with an undercut shoulder 22, the purpose and object of which will be hereinafter described. In the-event that a metallic connector such as 23 is tube-employed the same is adapted to extend through a metal cap 24,.'and is provided at its upper end with a threaded portion 25 having an opening 26 therein intovwhich the line conductor is adapted to extend and'by which the conductor is secured to the .connector bymeans of the nuts 21 and 28 and the lock nut 29. Slidably .received on the connector 23 between the shoulder por-- tion 30 and the nut 28 and adapted to overlie the cap 24 is a. metallic washer 3|, the latter being adapted to house a compositionwasher 32, the latter preferably being formed of felt or like material.

It will be understood from the drawing, particularly Figure 3, that interposed between the cap 24 and the upper end of the bushing 9 I provide ,another washer 33 preferably of compressible material such as cork, rubber, felt or the like. The opening 34 in the cap 24.is noncir'cular in outline and is adapted vto t the adje--` cent portion-'of the connector 23 so asto 'maintain the cap and connector against relative ro-` 'tation when the parts 'are in .fully assembled position. Thehead 9 of the bushing is'provided with a roughened surface `Ela which can be produced in any one of a number of ways, the simple method being to provide a sanded surface which, during the firing ofthe bushing becomes firmly. attached to ythe underlying surface of the bushing head. This rcughened surface of the head, the inner surface of the cap and the washer 33 are coated with red Glyptol or other suitableA lacquer, shellacor varnish .as desired. The parts are then assembledandpressure is applied to the cap until the-Washer 33 is compressed to substantially one-half its original thickness. When f the parts are maintained in this position the downwardly extending flange 35 of the cap 24 is then rolledor crimped so as to cause the inner surface to engage the undercut ,shoulder 22 of the head.` Pressure is then released and the expansion of-the Washer forces the'shoulder formed on the flange 35 against lthe shoulder 22 so as to providean exceedingly tight joint and as soon as the Glyptol, shellac or varnish has dried or set the cap is maintained in fixed position with reference to the bushing by a connection Aexternal force the washer forces the adjacent faces into tight engagement, and in this position the parts are sealed by the setting or hardening of the varnish or other compound. In the event the cap is perforated for lthe reception of the stem 23 I have found that the compressed washer will flow so as to embrace the said stem and form a gas and fluid tight joint.

The washer 32 serves to prevent the entry of moisture into the bushing and the bushing is now Afinished and ready for connection to a transformer or other electrical apparatus.

Having thus described my invention, particularly in reference to the preferred embodiment .thereof which I have chosen to illustrate, what I claim and desire to secure by Letters Patent is:

1. In combination with a bushing having a bulbous head, the lower inclined underlying surface of said head being roughened, of a metallic cap provided with a deformable skirt portion adapted to fit over said head, a compressible composition washer adapted to fit between the top of said cap and the upper surface of said head, means foradhesively securing together said head, washer and cap, said means comprising a lacquer, and means for connecting said cap and bushing, said last named means comprising the,

` the like wherein the bushing is exteriorly formed with an undercut head having an outwardly inclined underlying surface. and a plurality of spaced petticoats positioned below said surface, said bushing being interiorly formed with a 1ongitudinal bore, the combination of a single piece cap having the top aperture in alinement with said bore, a vdeformable peripheral flange depending from said top portion and adapted to be directly engaged Y with the outwardly inclined surface of said head, a compressed resilient washer interposed between said top portion and the adjacent surface of said head and forming a seal at the upper surface of said head, means for adhesively securing together said head, washer and cap, said washer being apertured in alinement withv said cap .aperture,fa metallic connector having an inner portion within said bore, v

and a stem projecting through said cap and washer apertures, a flange on said connector un derlying the vadjacent portion of said washer,

and removable means associated with said stem weg.

opening therein, a compressibie resilient Washer having a centrally disposed opening therein interposed between said cap and the upper surface of said head, means for adhesively securing together said head, washer and cap, said washer forming a seal, said washer also serving to maintain said interlocking portions of said cap in engagement with said head, a metallic connector provided with an inner portion positioned within said bore, said portion having a non-circular portion, and a stem extending through said apertures in said cap and washer, and means movably associated with said connector stem for drawing the same upwardly to engage said portion within the non-circular opening in said cap for preventing rotation of said connector when the parts are assembled.

4. An entrance bushing 4for transformers and the like wherein the bushing is exterioriy formed with a head adjacent one extremity thereof, the surface of said head forming the base of a truncated cone-shaped portion of said bushing,

the latter .also having a central longitudinal bore, the combination of a cap having a deformable skirt portion and a top portion, the latter being provided with an aperture therein, said top being spaced from the upper surface of said head, an apertured resilient Washer interposed between said apertured top portion and said last named surface, said deformable skirt portion being adapted to directly interlock with said coneshaped surface to retain said resilient washer under a predetermined compression, a metallic connector having the inner portion thereof positioned within said bore and having portions bearirg against said resilient washer, said connector having its stern extending through said cap and Washer apertures, resilient means surrounding said stem and positioned above said cap, and

v means rotatably associated with said connector stern for maintaining said connector in engagement withsaid Washer and said resilient means in engagement with said cap.

LELAND J. STEVENS.

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