US2228440A - Bushing - Google Patents

Description

Jan. 14, 1941.

L B. CHUBBUCK BUSHING Filed Oct. 26, 1939 INVENTOR leonara fi C/Iubbucrd O Force/01h WITNESSES: d I

Patented Jan. 14, 1941 UNITED STATES BUSHING Leonard B. Chubbuck, Hamilton, Ontario, Canada, asslgnor to Westinghouse Electric a Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 26, 1939, Serial No. 301,430 In Canada September 20, 1939 Claims.

The present invention relates to insulating bushings, particularly those for insulating the leads of high-tension electrical apparatus, and has particular reference to an improved closure cap for the exposed end of the bushing weathercasing.

Bushings of the type here involved usually comprise a substantially cylindrical shell of dielectric material, such as porcelain, through which extends the conducting lead or stud from electrical apparatus enclosed in an oil filled tank. The bushing is suitably secured to such tank in fluid tight relation and the outer end thereof is provided with a hollow cap, or expansion chamher, having a terminal for connection to an external circuit. Usually both ends of the conductor are fixed in relation to the respective ends of the dielectric shell, and in view of the different coeflicients of thermal expansion of these elements, destructive forces will occur upon changes in ambient temperature. This usually may be taken care of by a resilient connection between the conductor and one end of the shell but in all expedients which have been found successful, the resulting construction becomes quite complicated because, principally, of the necessity of maintaining the interior of the shell fluid tight to prevent the entrance of air and moisture due to "breathing" of the bushing upon changes in ambient temperature.

It is an object of the present invention to provide an improved bushing cap construction which, although it meets the requirements of the somewhat rigorous conditions encountered in service, is unusually simple in construction and inexpensive to assemble.

Other objects of the invention will be apparent from the following description read in conjunction with the accompanying drawing in which the single figure is a view in vertical section of the upper portion of a bushing surmounted by a cap constructed in accordance with the present inventlon.

Bushings of the type here contemplated may, by way of example, be of the type shown in the United States Patent No. 2,078,219, issued April 27, 1937 to G. A. Burr et al in which the conductor is surrounded by a wrapping of alternate layers of paper and conducting foil to constitute an insulator of the condenser type. As disclosed in that patent, the wrapping is sufliciently thick adjacent the midpoint thereof that it is hermetically sealed in a mounting flange which will be secured about the opening in the tank of a circuit breaker or transformer. A porcelain shell is supported at its lower end upon said mounting flange, and sealed thereto, and the upper end of the shell is closed by a cap having a terminal for connection to an external circuit.

In the accompanying drawing, the single flgure (Cl. ilk-l2) of which is a view in vertical section of a portion of a bushing embodying the invention, the conductor 2 extends through a porcelain shell or weather-casing 4 which may be provided with a plurality of creepage flanges 6 in a usual manner. It is to be understood that in the drawing only a portion of the upper section of the shell 4 is illustrated and the condenser wrapping starts below the cutoff portion of the conductor. It is to be understood, of course, that the invention is not limited to the condenser type of bushing which is referred to herein merely by way of example.

The shell 4 is surmounted by a cylinder 4 of transparent material such as glass gasketed or cemented as at III in a fluid-tight manner.

Normally, an insulating fluid i2, which may be oil or gum having the desired dielectric properties, fllls the casing around the conductor to-a point above the lower edge of the cylinder I whereby a visual indication of the height of such fluid is afforded. The outer end of the cylinder 8 is provided with a cap i4 and the latter is surmounted by a terminal l4 for connection to an external circuit.

In the present embodiment the cap comprises a relatively rigid metallic ring it having a depending peripheral lip designed to protect a asket 20.

The upper face of the ring it is provided with a plurality of upstanding lugs or projections 22 to constitute spaced seats for a stack of spring washers 24. One or more washers 24 may be provided depending upon the degree of resiliency desired, and the projections 22 engage the underside adjacent to the outer periphery thereof.-

A spacing member or sleeve 28 loosely surrounds the conductor 2 and is provided with a depending portion 24 at its lower end of approximately the same outer diameter as the internal diameter of the washers 24. This depending portion retains the washers 24 of the stack in proper superimposed relation upon the lugs 22. The spacing member 28 is enlarged to form an annular shoulder designed to bear upon the face of the upper washer 24 adjacent to its inner periphery.

The enclosure member for the base It, spacer 26 and washers 24 comprise a flexible metal housing 28 which may be spun, pressed or otherwise formed. In assembling the housing 29, before the cap is placed upon the bushing the base It, spring washers 24 and spacer 28 are assembled in operative relationship and the sheet metal is then spun or otherwise fltted over these elements to the shape shown with upper and lower inwardly extending flanges extending respectively over the top of the spacer 24 and the bottom of the base If. The lower flange is formed complementally to the under contour of the base and provides a seat for the cap upon the gasket 20. It should also be noted that the outer surface of the spacing member 26 is provided with a concave surface of revolution adjacent the upper end thereof and in the forming operation the housing 2! is shaped to conform to and closely embrace such surface of revolution. These elements may then be placed upon the shell 4 with the gaskets 20 in position, an upper gasket It placed on top of the assembly and the terminal it screwed down along the conductor 2. In the screwing down operation the spring washers 24 are depressed a sufficient amount so that upon expansion of the conductor 2 relative to the shell I there will always be compression exerted upon the gaskets 20 and 30, as well as upon any other gaskets between the spring and the mounting flange of the bushing, throughout the temperature range encountered in service.

The cap it may have soldered or otherwise suitably attached to it a threaded socket I2 for receiving one end of an arcing horn 34, and a filling plug 36 is also suitably secured to the wall of the cap I! as by soldering or brazing. When it is necessary to flll the bushing or add more liquid or gum thereto, it is introduced through the normally closed filling plug 36 and, in view of the spaced lugs 22 on the base II, it then flows into the interior of the shell 4. Similarly, the interior of the cap serves as an expansion chamber and the spaced lugs afford free fluid access to the interior from the shell I. By using a sheetmetal cap enclosure in accordance with the invention, a substantial reduction in expense results with an attendant simplification of design and assembly problems. Further there are no seams or bolted joints with the accompanying possibility of leakage, and the possibility of electrostatic stresses of a character to cause interference with radio broadcast reception.

The construction described is unusually simple, but at the same time effective, and various modifications of the specific construction shown may be resorted to without departing from the spirit and scope of my invention.

I claim as my invention:

1. In a bushing for high-tension electrical apparatus including a cylindrical shell of dielectric material having a conductor extending therethrough, a cap for closing the end of said shell comprising a ring-shaped base, resilient means paratus including a cylindrical shell of dielectric material having a conductor extending therethrough, a cap for closing the other end of said shell comprising a ring-shaped base, resilient means disposed around said conductor and supported by said base, a member surrounding the conductor and engaging said resilient means, a flexible metal enclosure having a side wall portion formed to the contour of a portion of the side surface of said member and a portion formed to the contour of the side of said base with a lower flange extending between said base and the end face of said shell, an upper flange on said enclosure engaging and overlying a peripheral portion of said member, and means acting on said member through said upper flange to compress said resilient means to resiliently clamp said flanges in operative position.

3. In a bushing including a cylindrical shell of dielectric material having a conductor extending therethrough, a cap for closing the other end of said shell comprising a rigid ring-shaped base, a gasket between said base and the end face of said shell, a spring washer surrounding said conductor supported adjacent its outer periphery on said base, a spacer member loosely surrounding said conductor and bearing at one end upon said spring washer adjacent to the inner periphery thereof, a terminal member threaded on said conductor to exert a force on said spacer member to deflect said spring washer a desired amount, and a flexible spun-metal enclosure having inturned upper and lower flanges disposed respectively between the top of said spacer and terminal member and between said base and said gasket.

4. In a bushing for high-tension electrical apparatus including a cylindrical shell of dielectric material having a conductor extending therethrough, a cap for closing the other end of said shell comprising a rigid ring-shaped base, a

gasket between said base and the end face of said shell, a spring washer surrounding said conductor supported adjacent its outer periphery on said base, a spacer member loosely surrounding said conductor and bearing at one end upon said spring washer adJacent to the inner periphery thereof, a terminal member threaded on said conductor to exert a force on said spacer member to deflect said spring washer a desired amount. and a flexible metal enclosure having inturned upper and lower flanges disposed respectively between the top of said spacer and terminal member and between said base and said gasket, said spacer having a depending lower portion fitting the opening in said spring washer.

5. In a bushing for high-tension electrical apparatus including a cylindrical shell of dielectric material having a conductor extending therethrough, a cap for closing the other end of said shell comprising a rigid ring-shaped base, a gasket between said base and the end face of said shell, a spring washer surrounding said conductor supported adjacent its outer periphery on said base, a spacer member loosely surrounding said conductor and bearing at one end upon said spring washer adjacent to the inner periphery thereof, a terminal member threaded on said conductor to exert a force on said spacer member to deflect said spring washer a desired amount, a flexible metal enclosure having internal upper and lower flanges disposed respectively between the top of said spacer and terminal member and between said base and said gasket, said spacer having a depending lower portion fitting the opening in said spring washer, and a longitudinally curved surface of revolution intermediate its ends. said enclosure being formed to closely embrace said surface.

LEONARD B. CHUBBUCK.

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