US2924644A - Electrical insulator links - Google Patents

Description

Feb. 9, 1960 J. E. cox

ELECTRICAL INSULATOR LINKS Filed April 20, 1953 United States Patent 0 .ELE'C'IRICAL-INSULATOR LINKS John Edward'Cox, Melbourne, Victoria, Australia Application April 20, 1953, Serial No. 349,710

2 Claims. (Cl. v174179) This invention relates to high-tension electric insulators, andis concerned with theconstruction of jointsbetween component parts of such insulators and between the insulator and its support, and in cases in which the. insulator suports an electric conductor, of'the joints-ibetweenthe insulator and such conductor. The inventionisparticularly applicable to high tension insulators subjected to mechanical load ortension, such as the links of a: high tension insulator chain and to insulating bushings, such as bushings for transformer tanks or, in general, bushings which have to take conductors through a wall or partition with a gas-, wateror oil-tight joint. Hitherto such joints have usually been made by'employing cement between the insulator and acomponent part, often with a cushion between them, such as a layer of bitumen or hemp or a keying of glazed porcelain particles. Metal parts have also been secured to insulatorsby molten lead or other soft metal, and in joining the components of multi-part insulators more than one ofthe above methods are sometimes usedin combination.

The object of the present invention is to provide a simple and reliable joint for the above purposes, which can be made liquidor gas-tight and, as already indicated, can be applied to insulators which have tobe'subjected to considerable mechanical tension.

Thus, according to the present invention, the joint between the two parts to be connected-whether it is to be between metal and insulator orinsulator and insulatoris formed by one or more'resilient rings of yielding material, such as natural rubber, synthetic rubber particularly neoprene, thermoplastic. synthetic resin and so forth. The ring is inserted between the two parts to be joined which are made to fit Welltogether in telescoping relation so the ring or rings when in position is compressed between the two closely-spaced surfaces and forms the-necessary joint. The ring, or rings, is seated in oneor more annular grooves formed in one of the cooperatingsurfaces of the parts to be joined. The provision of'such grooves serves definitely to locate the rings and to prevent them being displaced, and also ensures that the distortion of the rings is localized to make a goodjoint by being firmly pressed into the narrow gap between the cooperating surfaces.

In the case of an insulator to be placed under tension, for example a link of an insulator chain, the tension member is secured to a metal terminalat either end and is enclosed in an insulating housing, such as a glass or porcelain tube. The terminal members may have outer sleeves which make joint-with the insulating housing in accordance with the invention, for example by the use of rings located in grooves in these sleeves of the terminals. Also, at one or both ends, the terminals may have an inner surface which makes joint with the inner tension member also by means of one or more of the yielding rings.

Also, in the case of transformer bushings or like structures for indoor or outdoor use, the joint at either end between the conductor and the insulator may be made with metal members which have an inner surface making joint with the conductor and a sleeve engaging outside the insulatonthe joint being made in both cases in accordance with the invention, by one or more yielding rings. In the case of a tank bushing, a metal member secured to the coveror wall of the tank may also have an inner cylindrical surface which makes joint with the insulator by one or more rings in accordance with the invention as already indicated.

In order to'illustrate the invention in more detail, some examples thereof will now be described more fully with reference to the accompanying drawings, in which:

Figure 1 is an axial longitudinal section of a link for a high tension insulator chain;

Figure 2is a transverse section on the line 11-11 in Figure 1;

Figure 3 is an axial section showing a modification of the attachment of the link as an alternative to that at the lower end of Figure 1, and

Figure 4 is a longitudinal axial section of a transformer bushing in accordance with the invention.

Referring first of all to Figures 1 and 2, in this case the internal tension member 1 consists of a rod of wood which has been impregnated with a synthetic resin forced under pressure into thepores of the wood. This material may be beech wood impregnated with an insoluble phenolformaldehyde resin, such as the material known in the trade as Permali. It has a somewhat octagonal section along its main length, but at each end has a circular part 2 arranged to be-screw-threaded into the terminal member or socket 3, 4 and secured by pins 5. The upper member 3 is formed at its outer end with a socket 6 of a ball joint intended to receive the head 7 of the adjacent link. The terminal 3 is conveniently made as a malleable iron casting and galvanized.

The lower terminal member 4 which bears the head 7 may be a mild steel forging, and as it has to make joint with a cap 8 and requires an accurate outer surface, it may be cadmiurn plated.

Since the tension member 1 has to sustain considerable tension, the terminal members 3, 4 have relatively long inwardly extending sockets into which the cylindrical ends 2 of the members 3, 4 are screw-threaded. The outer housing or container is, in this case, a glass tube 9 with a fairly accurate outer surface which, at the upper end,

is enclosed by the outer sleeve 10 of the terminal member -3. At the lower'or head end of the link, the cap 8 also has a sleeve 11 engaging the outer surface of the glass tube 9, and this cap may conveniently be made of aluminum. Thus, the outer sleeve 11 andthe inner member 12 of the cap 8 which haveto'make joint respectively with the outer surface of the glass tube 9 and the stem 13 of the terminal member 4, are each formed with two shallow annular grooves in each of which is lodged a resilient ring 14, '15 which, in this example, is of neoprene. The rings stand out from their grooves so as to be compressed when the cap 8 is fitted 'over the glass tube 9 on the one'handand'the stem 13 on the other. It isimportant to formthe glass tube 9 with a bevelled or chamfered part 16 at either end, and toform the stem 13 with a chamfered part 17'to aflord an easy entry of the tube 9 and stem '13 into the grooved surfaces of the cap 8, so that whenthe cap slides on to these two members, oil-tight'joints'areformed by the rings 14, I5.

Atthe'upperorsocket end, the terminal "3, .as already mentioned,.is in one piece with the socket 6 and, in .this case also, two grooves are formed on the inner surface of the sleeve 10 to receive similar resilient rings 18 which thus make joint between the terminal member 3 and the outside of the glass tube 9.

It is possible to provide a filling hole for filling the glass casing 9 with good quality insulating oil, but this is not necessary in the construction shown because the unit may be filled with oil or inert powder during assembly as follows: The rod 1 is screwed into the socket of the terminal member 3;. the rings .18 are placed in their grooves and the glass. tube 9 at its upper end inserted into the sleeve 10, the chamfer 16 assisting. in this without disturbing the rings 18. Then with all the parts in position except the lower terminal cap 8, the casing 9 is filled with oil while the unit is inverted in relation to Figure 1 of the drawings and, finally, the terminal cap 8 with the rings 14 and 15 in position is caused to slide on to the glass tube 9 and the stem 13 of the terminal 4.

In experiments made with a link constructed as above in which the screw-threaded ends of the rod 1 were about 1.4 inches in diameter, it was found that the flash-over voltage was about 160 kilovolts and the corona. level about 150 kilovolts. Thus the corona level is very much higher in relation to the flash-over voltage than is usual in other forms of insulator links.

Other forms of terminal members may obviously be used with the same general internal construction. Thus, if an insulator of this construction is to be used in compression, for example for supporting a radio tower, the terminal members 3 and 4 would then be shaped at their upper ends with flat discs or flanges suitable for seating on a suitable surface.

Sometimes, from the point of view of mechanical strength, it is desirable to fit such a device with clevis terminal members. In the case of the upper teiminal shown in Figure 1, it is only a question of casting the terminal member 3 with the central member of a clevis or a fork. However, at the lower end of Figure l, the construction needs some more modification and an example of this is shown in Figure 3. In this figure the lower end of the glass tube 9 and the screw-threaded end 2 of the rod 1 are shown as well as the lower terminal member 4. However, the extreme lower end of the member 4v is now shaped somewhat differently, being bored at the bottom and tapped to receive the screw-threaded stem of the fork or clevis 19 which is screwed into the member 4 and is secured by a pin 20. The sealing member 8a which serves the same purpose as the member 8 in Figure 1 is now of somewhat different shape. It makes a joint with the glass tube 9 by a pair of rings 14a as in Figure 1, but instead of being turned inwardly it is formed with a downward extension to make joint with the stem 13 of the member 4. In this case, however, joint rings 15a are lodged in grooves in the stem 13 and not in the member 8a. As a matter of fact at all of the joints shown in Figures 1 and 3 the grooves could be made in the opposite member except, of course, that it is not very convenient to form annular grooves in the glass tube 9.

In Figure 4 which shows the invention applied to a transformer bushing, joints which are gas-, waterand oil-tight have to be made between the porcelain insulator 21 and the conductor 22 of the bushing both outside and inside the transformer tank, the cover of which is indicated at 23. Also a similar joint has to be made between the insulator 21 and the cover 23. At the outside of the tank, there is a jointing member 24 consisting of a non-ferrous casting formed with internal annular grooves to receive one pair of the yielding rings 25 which make joint with the conductor 22, and another pair of rings 26 which make joint with the outside surface of the insulator 21 in much the same way as in Figure 1. A similar non-ferrous casting 27 is used inside the tank and formed with grooves to receive one pair of yielding rings 28 for making joint with the conductor 22, and to receive another pair of rings 29 making joint with the outside of the insulator 21 exactly at the top. In order to make joint with the tank cover 23 a flanged member 30 is secured by bolts 31 to the cover 23 and has a pair of annular grooves to receive a pair of yielding rings 32 for making joint with the outside of the insulator 21.

The insulator 21 is shown with the usual sheds 33. In Figures 1 and 3 the glass tube 9 is shown with a smooth outer surface but it may be provided with sheds to increase the creepage path along it, and also either or both of the end members 10, 11, may, if desired, be formed with inclined rain sheds.

I claim:

1. A high tension electric insulator link comprising an insulating elongated tension member comprising an insulating rod, an insulating tubular housing surrounding said tension member, a terminal member at each end of said tension rod the end portions of which are threaded into said terminal members, at least one of said terminal members being formed as a cap and with a skirt closely embracing the end of said housing and the cylindrical engaging surface of at least said housing or said cap being formed with an annular groove and a yielding jointing annular gasket housed in said groove and dimensioned so as to be compressed between the closelyspaced surfaces of said housing and said cap upon said housing and said cap being telescoped together, said gasket also being dimensioned so as to fill completely said groove after said housing and cap have been forced together and being substantially completely confined be tween said housing and the skirt of said cap.

2. A high tension electric insulator link comprising an" insulating elongated tension member, an insulating tubular housing surrounding said tension member, a terminal member at each end of said tension member and secured to the latter, said terminal member at one end being formed as a cylindrical stem and said terminal member at the other end being formed as a cap and with a skirt closely embracing the end of said housing, a second 'cap formed with a skirt embracing the opposite end of said housing and with a sleeve closely embracing said first mentioned terminal member, each of said skirts and said sleeve being formed with a pair of annular grooves on their inner surfaces and a plurality of pairs of yielding jointing annular gaskets housed in said grooves and respectively dimensioned so as to be compressed between the closely-spaced surfaces of each of said skirts and said housing and of said sleeve and said cylindrical stem upon said respective parts being telescoped together.

References Cited in the file of this patent UNITED STATES PATENTS 1,876,581 Austin Sept. 13, 1932 1,983,335 Austin Dec. 4, 1934 2,284,530 Meyer May 26, 1942 2,429,426 Phillips et al. Oct. 21, 1947 2,443,545 Schwennesen June 15, 1948 2,452,580 Lee Nov. 2, 1948 2,552,686 Melcher May 15, 1951* FOREIGN PATENTS 25,613 France Apr. 21, 1923 (1st addition to 540,916)

OTHER REFERENCES Publication: Parker O-Rings and Special Seals, The Parker Appliance Company, Catalog 903, October 1950, page 42.

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