US2428456A

US2428456A - Enameled insulator bushing

Info

Publication number: US2428456A
Application number: US500212A
Authority: US
Inventors: Waldo W Higgins
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1943-08-27
Filing date: 1943-08-27
Publication date: 1947-10-07
Anticipated expiration: 1964-10-07

Description

1947- w. w. HIGGINS' 7 2,428,456

ENAMELED INSULATOR BUSHING Filed Au 27, 1945 2 Sheets-Sheet 1 rm 1 e "Kw/M ATTORNEY.

'Oct. 7, 1947.

W. W. HIGGINS ENAMELED INSULATOR BUSHING Filed Aug. :27, 1943 2 Sheets-Sheet 2 [nun/1 ATTORNEY Patented Oct. 7, 1947 ENAMELED INSULATOR BUSHING Waldo W. Higgins, Whitefish Bay, Wis., assignor to A. 0. Smith Corporation, Milwaukee, Wis., a corporation of New York Application August 27, 1943, Serial No. 500,212

8 Claims.

This invention relates to enameled insulator bushing.

One of the objects of the invention is to provide a bushing of th cone shaped multiple disc type in which the discs are separated by and joined to one another by ceramic enamel in a manner similar to the flat disc bushing of applicants copending application Serial No. 441,199, filed April 30, 1942, and issued August 6, 1946, to Patent No. 2,405,425.

Another object is to prevent the setting up of injurious stress in the enamel upon contraction of the discs and of the insulator in cooling from the temperatures employed in joining the parts.

Another object is to provide a method of constructing and assembling conical-shaped discs for such an insulator, without distortion.

Other objects and advantages of the invention will appear hereinafter in connection with a description of an embodiment of the invention illustrated in the accompanying drawings.

In the drawings:

Figure 1 is a side elevation of the insulator, partially in section;

Fig. 2 is a similar View of the parts prior to joinder and in spaced relation during assembly;

Fig. 3 is a similar view showing the parts assembled and weighted preparatory to firing;

Fig. 4 is an enlarged fragmentary sectional view similar to Fig. 3; and

Fig. 5 is a view similar to Fig. 4 after firing.

The insulator comprises a conductor bushing I with a shank 2 and an integral conical skirt 3 into which a plurality of conical insulating discs or plates 4 fit. A core plate 5, of conical shape fitsinto the last disc 4 and has a tubular shank 6 with a base 1.

The skirt 3, discs 4 and core plate 5 are coated with a high dielectric ceramic enamel 8 fused thereto, as generally set forth in applicants copending application. The enamel coating 8 extends over the meeting surfaces of the parts and the inner edge surfaces thereof to provide a continuous insulation therebetween. The coating 8 is crowned at the central circumference of th respective meeting surfaces as set forth in said prior application and in applicants copending application Serial No. 441,201, filed April 30, 1942, for Joinder of porcelain enameled products and issued July 2, 1946, to Patent No. 2,403,079.

The skirt 3, discs 4 and core plate 5 have outward flanges 9 extending in planes perpendicular to the axis of the bushing and which may be thinner than the respective conical body mem- 2 bers to effect substantial spacing of the same so that they need not be completely covered with dielectric enamel. It is preferable, however, to coat these with a thin coating of enamel to prevent scaling of the metal and possible injury to the seal thereby.

The parts are assembled for joinder as indicated in Figs. 2, 3 and 4 with the crowns of the coating 8 on the conical surfaces of the parts under pressure contact from the Weight of the several parts and from the additional weight It! applied on the top of the assembled structure.

A ring H is lowered onto the upper surface of the flange 9 on skirt 3, and has downwardly depending vertical rods l2 which engage the edges of the several flanges 9 to keep all of the parts in vertical alignment. The number of rods I2 employed may vary from three to several times that number depending upon the size of the bushing, and the rods are uniformly spaced circumferentially about the structure.

Spacer blocks or washers i3 are assembled on each rod l2 and disposed loosely between the several flanges 9 at the time the discs are assembled, there being one washer between each two adjacent flanges on each rod. The washers 13 are constructed of accurate thickness to limit the coming together of the parts by softening and squashing of the enamel crowns during heating, so that the parts are kept concentric and in alignment and the required thickness of enamel is maintained between the parts.

After the parts have been assembled, as shown in Figs. 3 and 4, they are heated in a suitable furnace to a temperature sufficient to effect an enamel flow, but substantially lower that the original firing temperature of the enamel. The heat softens the enamel coatings and they flow together allowing th parts to come together under the weight [9 and the weight of the parts and the ring ll, rods I2 and spacers l3.

This lowering of the parts relative to one another continues until the flanges 9 engage the several spacer blocks [3 beneath them, thereby limiting further movement of the flanges. At this time the several flanges are supported 0n the flange of core plate 5 by means of the several spacers l3.

The structure is then cooled and. thereafter the weight [0, spacers l3 and ring H are removed. In order to prevent any undue stress being set up in the enamel upon cooling, the spacer blocks l3 should be constructed of a metal having a higher coefflcient of thermal expansion than the metal of the parts and the enamel. This will result in a contraction of the spacers I3 during cooling in excess of the contraction of the bushing, so that as soon as the enamel becomes sufficiently strong upon cooling it can assume the load without being tensioned by the spacer blocks, and the latter can be readily removed without injuring the structure.

The weight employed for eifecting interfusion of the enamel coatings should be selected with regard to the strength of the flanges 9 at the high temperatures employed, and should not be sufficient to deflect or distort the flanges. The flanges 9 may be continuous around the circumference, or they may be discontinuous in the form of projecting lugs.

The spacers 13 may be employed to advantage in the construction of flat disc bushings of the type set forth in applicants copending application above referred to.

The invention may have various embodiments within the scope of the accompanying claims.

I claim:

1. An insulator bushing of the cone-shaped multiple plate type comprising cone-shaped metal plates coated with ceramic enamel and having circumferential flanges disposed in planes at right angles to the axis of the structure and separated to provide for receiving spacing means therebetween during assembly and interfusion of the enamel coating.

2. In the fabrication of insulator bushings of the ceramic enameled multiple disc type, the employment of spacers of a thickness corresponding to the final axial spacing of the disc edges between the edges of the discs to prevent distortion of the structure during interfusion of the enamel coatings under pressure and determine the final thickness of enamel between the discs.

3. In the fabrication of insulator bushings of the ceramic enameled multiple disc type, the steps of assembling the discs with their coatings in pressure contact, positioning spacers loosely between the outer edges of the discs and distributed about the circumference thereof, heating the structure to soften the enamel and eifect th'e interfusion of the coatings until said spacers become engaged by the respective discs and limit further movement thereof, cooling the structure, and removing the spacers.

4. In the fabrication of insulator bushings of the ceramic enameled cone-shaped multiple plate type, the steps of assembling the plates with their axis vertical, applying a predetermined pressure weight on top of the assembled structure, applying spacer blocks of predetermined thickness corresponding to the final axial spacing of the outer edges of the plates between the corresponding outer edges of adjacent plates and distributed about the circumference thereof, heating the structure to interfuse the enamel coatings on the adjacent plates while limiting the flow of the enamel by said spacer blocks, and thereafter cooling the structure and removing the blocks.

5 In the fabrication of insulator bushings of the ceramic enameled multiple disc type, the employment of spacer blocks of predetermined thickness corresponding to the final spacing of the discs between the discs to limit the flow of the enamel during interfusion thereof, and distributing said blocks uniformly about the circumference of the structure.

6. In the fabrication of insulator bushings cf the ceramic enameled multiple disc type, the steps of placing spacer blocks of predetermined thickness adapted to determine the final spacing of the discs and of a metal having a greater coefficient of thermal'expansion than that of the assembled structure between the discs to limit the flow of the enamel during interfusion thereof, heating the structure to soften and interfuse the enamel coatings of the several discs, and thereafter cool ing the structure and thereby loosening the spacer blocks by reason of their greater contraction than the structure, and removing the spacer blocks.

7. In the fabrication of insulator bushings of the ceramic enameled multiple disc type, loosely positioning spacer blocks between the assembled enamel coated discs, heating the structure to eifect a flow and interfusion of adjacent coatings While limiting the flow by means of said spacer blocks, cooling the structure, and contracting the thickness of the spacer blocks during coohng at a faster rate than the contraction of the structure to loosen the blocks for removal and prevent stress being set up in the structure by reason of the contraction of the same upon the blocks.

8. In apparatus for use in assembling ceramic enameled multiple disc insulator bushings, spacer blocks of predetermined thickness relative to the spacing of the discs to determine the final thickness of the enamel between the discs upon the fusion of the enamel 'by heat and pressure, and constructed of a metal having a greater coefficient of thermal expansion than that of the finished structure.

WALDO W. HIGGINS.

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

UNITED STATES PATENTS Number Name Date 1,997,109 Fyfe M Apr. 9, 1935 2,262,831 Burleson Nov. 18, 194.1 2,317,799 Pereles d. Apr. 27, 1M3 1,562,533 eintraub I Nov.2-l,1925 1,887,181 Cone Nov, 8, 1932 1,259,384 Fortescue Mar. 12, 1918 FOREIGN PATENTS Number Country Date 253,575 France 1924 (3rd addition to No. 559,864)