US3184634A - Lightning arrester with a resilient seal between the gaps and resistive material - Google Patents

Description

May 18, 1965 s. s. KERsHAw. JR I LIGHTNING ARRESTER WITH A RESILIENT SEAL BETWEEN THE GAPS AND RESISTIVE MATERIAL Filed Jan. l5. 1961 2 Sheets-Sheet 1 INVENTOR. Szwy 5, Kers/zaza J5.

M f @ym yzfofvzcjf May 18, 1965 Filed Jan. 13, 1961 S. S. KERSHAW. JR LIGHTNING ARRESTER WITH A RESILIENT SEAL BETWEEN THE GAPS AND RESIS'IIVE MATERIAL 2 Sheets-Sheet 2 INVENTOR. Stanef 5. Hens/mw (/7:

United States Patent O LIGHTNENG ARRESTER Wl'lH A RESILEENT SEAL BEN/VEEN '1HE GATS AND RESiSilVE lt/lA'lfFilillAL Stanley S. Kershaw, Jr., Milwaukee, Wis., assigner to McGraw-Edison Company, Milwaukee, Wis., a corporation of Delaware Filed Jan. 1.3, 1961, Ser. No. 32,517 Claims. (Cl. 315-36) This invention relates generally to overvoltage protective devices and more particularly to improvements in valve type lightning arresters.

Valve type lightning arresters in general involve a housing which is connected at one end to the line to be protected and at the other end to ground, and which contains therein a plurality of serially connected are gap structures in series with a non-linear valve element. r'he series gaps in the arrester isolate the line from ground until subjected to sufficiently high voltages (usually lightning surges) at which time they spark over. The valve element may be considered as having a high apparent resistance to power frequency currents but a low apparent resistance to surge current flow therethru and serves to discharge surges and to subsequently limit follow current to a magnitude which the series gaps can interrupt.

Contemporary valve type arresters have tamped or preformed valve elements positioned near the ground end of the housing and gap structures seated atop the valve element at the line end of the arrester. These valve type arresters have, on occasion, experienced valve element flashover during overvoltage discharge operation which has resulted in failure of the arrester. This has been due to the fact that ionized gases produced in the area of the gap structures during sparkover have drifted in between the valve element and the housing thereby producing a conductive path around the valve element.

Another problem encountered in certain conventional arresters is that moisture given off by the valve element during arrester operation tends to increase the humidity in the vicinity of the gap structures thereby decreasing the power frequency sparkover of the gap structure.

In valve type arresters the spacing of the electrodes defining the gap is extremely important in maintaining a predetermined gap sparlrover characteristic. From the time that these type arresters are shipped from the factory until they are withdrawn from service it is imperative that the gap distance be preserved. Conventional valve type arresters Which have experienced severe physical shocks in transport or While in operation have failed to provide adequate overvoltage protection due to a variety of factors ranging from alteration of the gap dimension, resulting in consequent changes in the gap sparlrover characteristics, to displacement of the gap structure, resulting in ruptured housings. Some difficulty has also been experienced in initially centering the gap structure in the housing, which if not done correctly makes the above mentioned conditions more probable.

It is, therefore, an object of the invention to provide a lightning arrester which will not experience valve element flashover.

Another object of the invention is to provide a lightning arrester which will retain a given gap dimension under high physical shocks.

Another object of this invention is to provide a lightning arrester in which initial centering of the component parts thereof is facilitated.

A further object of this invention is to provide a structure which Will achieve all the foregoing objects without in any way interfering with the normal function of the lightning arrester and which is economical to produce and which may be adapted for usage with existing lightning arrester constructions.

3,184,634 Patented May 18, 1965 Cce Other objects and advantages of my invention will be apparent from the following description of the preferred embodiments of the invention taken in conjunction with the accompanying drawings in which:

FIG. l is a partially cutaway View in elevation of the invention incorporated in one type of valve type lightning arrester;

PEG. 2 is a partially cutaway perspective View of the invention;

FIG. 3 is a cutaway view in elevation of the device of FIG. 2;

FIG. 4 is a cutaway view in elevation of another embodiment of the invention as it would appear positioned within a lightning arrester housing;

FlG. 4a is a partially cutaway view in elevation of the device of FlG. 4 prior to insertion thereof in a lightning arrester;

FIG. 5 is a partially cutaway view in elevation of still another embodiment of the invention as it Would appear positioned within a lightning arrester housing;

FiG. 5a is a partially cutaway view in elevation of the device of FIG. 5 prior to insertion thereof in a lightning arrester;

FIG. 6 is a partially cutaway view in elevation of two modified forms of the device in conjunction with a spark gap structure as they would appear positioned within an arrester housing;

FIG. 7 is a cutaway view in elevation of the upper device of FIG. 6 prior to attachment thereof to a spark gap structure;

FIG. 8 is a cutaway View in elevation of the lower device of FIG. 6; and

FIG. 9 is a partially cutaway view in elevation of another somewhat niodiiied form of the device in conjunction with a spark gap structure.

Referring now to FIG. 1, ifi indicates a valve type arrester generally which comprises a cylindrical housing 11 of porcelain or other insulating material which may be skirted, but this is not shown. Within the lower portion of the housing are valve material blocks 12 which may be of non-linear resistance material such as siliconcarbide. The lower portion of the housing 11 may be enclosed by a cap 13 from which a circuit disconnecting device 1d and ground lead connector 21 project. The cap 13 may be attached to the housing 11 as is shown or may be an integral portion of the housing.

Seated atop the upper-most valve block 12 is a conductive isolating and centering device 15 which will subsequently be explained in more detail. In contact with the device 15 is a gap structure 16 which is inwardly spaced from the inner periphery of the housing 11 and which comprises spaced apart insulating, electrode support members 17. Afiixed to the members 17 and extending therebetween in spaced apart relation are disk electrodes 18 having an embossed arcing surface 19 on both sides thereof. The embossed arcing surfaces 19 on adjacent electrodes 18 dene therebetween spark gaps 20.

The upper and lower-most electrodes 18 have only one embossed portion 19 thereon which projects in a direction toward the embossed portion of the next adjacent electrode. The electrodes 18' are affixed to the outer surfaces of members 17 and serve to provide a stable gap structure.

Above the upper-most electrode 18 and in Contact therewith is a second conductive isolating and centering device 15 which is biased against the upper face of the electrode 1S by a compression spring 22. Interiorly of the compression spring 22 is a shunt member 23 which is in electrical contact with the upper isolating and centering device 15 and which contacts a conducting enclosure cap 2d which is fastened to a raised annular portion Z5 on the outer periphery of the housing 11. A synthetic rubber gasket 26 may be positioned between the cap 24 and the housing so as to permanently seal the housing against the entrance of moisture. An insulating cap I3 is fitted over the conducting cap 24 and serves as a seat for the line terminal conductor 27 which is in electrical contact with the shunt member 23.

FIGS. 2 and 3 show the conducting isolating and centering device l which comprises a circular metallic conducting plate 3h, a washer shape circular elastic member 3l having a larger diameter than that of the plate 3h, and a second plate-like conducting member 32 of substantially the same diameter as the plate Si) and having a recessed center portion 33 and a raised annular portion 34. An enlarged aperture 35 is provided in the center of the elastic sealing member 3l so that when the member 31 is interposed between the conductive members 39 and 32, portion 33 of member 3?; projects thru the aperture in elastic member 31 thereby contacting the other metallic plate 3d. The portion 33 of member 32 may be spot or projection welded, as at 35, to member Elli. Apertures Sil' and 32 may be provided respectively in members Sil and 32 and are primarily utilized to align the members 30, 31 and 32 prior to welding. However', they may be utilized to fasten the assembly together by a rivet or similar means thereby eliminating the weld but this is not shown to shorten the disclosure and to facilitate the understanding thereof. The elastic member Si may be of rubber, neoprene or similar materials while the members 3l) and 32 may be of stainless steel or other similar conducting materials.

As can be seen from FIG. l the assembly 15 is placed within the housing ll on either end of the gap structure. Since the diameter of the circular elastic member 3l is in lexcess of the bore diameter of the housing, the member 31 will take on a saucer-like shape when placed in the housing (shown by the dotted lines in FIG. 3). That is, the outer area of the member 3l starting with the point of emergence of the member from members 3) and 32, will achieve an arcuate shape. The relatively resilient insulating member 3l is deformed from its original shape when placed in the housing and in attempting to regain its original shape bears against the inner walls of the housing in such a manner that a relatively air-tight seal is initiated therebetween. (Note that apertures 3h and 32 thru the assembly l5 are effectively plugged up by positioning either or both electrode member l5 and the valve block 12 flush against one or the other of the metallic plates.)

This air-tight seal will prevent gases, evolved during sparkover of the gaps, from passing into the area of the valve blocks and thereby tending to provide a condition between the blocks and housing walls which is conducive to block ashover.

This physical isolating of the gap structure is accomplished without in any way altering the electrical characteristics of the arrester since the assembly l5 when properly positioned serves as a conducting member (due to the fact that the conducting members on either side of the resilient insulating member are in electrical contact with one another) as well as serving as an isolating means for physically, but not electrically, isolating the gap structure from the remainder of the arrester.

The above described device is particularly versatile in that it may be inserted in a variety of different size housings while still adequately performing its physical and electrical duties. This is so, as long as the diameter of the resilient member 31 is somewhat in excess of the bore diameter of the housing.

In addition to the above function, the device l5 also serves to center the components of the arrester by exerting a downward force relative to FIG. 1, as a result of the impingement thereof (member 3l) against the walls of the housing. The upper assembly l5 of FIG. 1 separating the spark gap chamber from the compression spring, in particular, serves to downwardly bias the ladder gap structure thereby centering same. In conjunction with the centering function of the assembly l5, the assemblies also serve to cushion the gap structure against transverse physical shocks which otherwise could damage the electrodes or alter their alignment.

While the isolating and centering device is shown only in conjunction with a gap structure having spaced apart support members it is just as adaptable to use with a valve type arrester which utilizes individual resistive spacers be tween adjacent electrodes or to a valve type arrester of the type which has a valve element interposed between spark gap structures.

FIGS. 4 and 4a disclose a slightly modified centering and isolating device 4th which has all the advantages of device l5 but which differs therefrom slightly. The device 40 comprises a substantially spherical resilient insulating member 4l which may be of neoprene, rubber or the like. As is evident in FIG. 4a opposed portions of the sphere are removed to provide two apertures 42 therein. An assembly comprising spot welded together circular conducting plates 43, 44 and 45 is inserted in each aperture so that the plate 43 is within the confines of the member 4i while the plate 45 (which has a larger diameter than that of the plate 43) is without the confines of member 41 (FIG. 4a). While the plates 43, 44 and 45 are shown as being spot welded together it is conceivable, consistent with the invention, to provide an integral plate assembly having a portion -thereof designed to protrude thru apertures 42 into the contines of member 41 and another enlarged portion which is in electrical contact with the protruding portion but which is precluded from entering the contines of member il by its size (i.e., the diameter would be in excess of that of the apertures 42 in member 4l) but this is not shown as the spirit of the invention is illustrated by FIGS. 4 and 4a.

When properly positioned in a lightning arrester housing similar to that of FIG. 1 and arranged in the manner of devices l5, the device 40 will assume the shape shown, in FIG. 4. That is, the 4two plates 43 will contact each other as the result of the forces applied to the plates 45 thereby forcing the periphery of member 41 against the housing il and into the shape 42 (FIG. 4). It can thusly be seen that when the device 40 is positioned in a lightning arrester and subsequently compressed that the portion 4i of the resilient member will move out and bear against the interior of the lightning arrester housing thereby initiating a relatively air-tight seal therebetween.

The devices of FIGS. 4 and 4a are particularly advantageous in that subsequent to insertion in a lightning arrester and prior to compression of the device the plate assemblies may be rotated with respect to the resilient member to thereby provide a better alignment of parts Within the arrester housing. Even after compression of the device has been accomplished (bringing members 43 into contact with one another) either or both of the plate assemblies may be rotated with respect to the resilient member without breaking the seal between same and the arrester housing.

While it is not shown, a coil spring (tension) or similar resilient means may be placed between the contact plates 43 within the confines of member 4l. This coil spring provides a method of taking up tolerances along the housing lengths, of aiding the seal between the resilient member and the housing particularly when internal diameter tolerances are small, and of providing internal holding pressures between the contact plates while maintaining electrical contact thru the seal.

Referring now to FIGS. 5 and 5a, another modification 5i? of the invention is shown which comprises an insulating member S1 of a molded rubber component or similar material which is dish-shaped or which is substantially hemispherical in shape. An aperture 52 extends thru member Si and an annular rim 53 surrounds the upper portion of the member defining the aperture. A contact member S4 which may be of steel or other conducting ma terial comprises a cylindrical plate-like member 55 which has an upper annular portion 56 having an enlarged diameter. The member 54 extends thru the aperture 52 in member 51 with annular portion 56 being received in the annular rim 53 of member 51 as shown in FIG. 5a.

When positioning the device within the housing of a lightning arrester a metallic conducting disk 57 (which may be an electrode of the gap structure) is iirst positioned in the housing and then the device du is inserted in the housing in such a manner that the walls of the hemispherical resilient member 51 are compressed (FIG. 5) thereby allowing the lower portion of the member 55 to contact the upper surface of the conducting disk 57. It can be seen that in this position (FIG. 5) that a seal is initiated between the walls of the resilient insulating member and the housing while at the same time an electrical current path -thru the seal is maintained.

Since the open cup portion of the resilient member is inserted in a downward direction in the lightning arrester body any increased pressure from below the seal tends to increase the sealing pressure of the seal by forcing the outer periphery of the resilient member against the inside wall of the housing. The fact that this is accomplished is mainly due to the unique conguration of the resilient member which allows the outer periphery of same to be inserted conveniently in the housing.

In FIG. 6 a gap structure 16 is shown which comprises a plurality of spaced apart electrodes 18 which are positioned between electrode support members 17' within a housing '11. The general gap structure is substantially similar to that of FIG. 1 and functions in the same manner. However, slightly modified forms of upper and lower conductive isolating and centering devices are utilized in conjunction with the gap stucture 16.

The upper device 60 (FIG. 7) comprises a conducting plate 61 having a raised annular portion 62 and a dishedout center portion 63 having a central aperture 6a therein. A washer shaped relatively elastic member 65 of a diameter larger than `that of the plate 61 and having an aperture 66 thru the center thereof of a diameter in excess of that of the center portion 63 of plate 61 is positioned below the plate 61 in such a manner that center portion 63 of the plate protrudes thru the aperture 66. An electrode member 67 having an embossed central portion 68 is afiixed as by a spot weld 69 lto the underside of plate 6l so that `the embossed portion 68 lies substantially beneath the aperture 64. Gripping members 70 and 71 are provided on certain opposite sides of the electrode 67 and are adapted to engage the support members 17 so as to provide a stable structure. Members 71 (FIG. 6) are bent inwardly from the position of FIG. 7 when engaging the support members.

The lower device 60 (FIG. 8) is similar to the device 60 of FIG. 7 in that a lower conducting plate 6l having an annular portion 62', a recessed central portion 63 and an aperture 64 is provided on one side of an elastic barrier member 65 having an enlarged central aperture 66. A second conducting plate 72 is positioned on the other side of the elastic member and has a central aperture 73, a notched peripheral portion 74 and support gripping members 75. A spring assembly 76 having a central aperture 77 is positioned on the upper side of the second conducting plate. The whole assembly is attached together by a conducting member 78 (similar to the previously discussed embossed portions) which projects well above the plate 72 and which extends thru the apertures 77 (spring), 73 (second plate), 66 (elastic member) and 64 (lower conducting plate) and which is iared out (dit) against the lower surface of plate 61 so that the assembly is iirmly held between the ilared out portion t) and an upper shoulder portion 81 which rests upon the area of the spring assembly which defines the aperture 77. The complete assembly is then positioned so that the ends of the spring 76 and the support gripping members 75 engage opposed sides of the support members 17 with the corners 6 of same positioned in the notched peripheral portions 74 of the conducting plate 72.

It can be readily seen that the basic difference disclosed in the embodiments of the device illustrated in FGS. 6-8 is that the isolating conductive and centering device is aiiixed directly to the gap structure with a portion of .the device forming the upper or lower (as the case may be) electrode of the structure.

These modifications have the particular advantage that the gap structure may be centered as it initially is inserted within `the housing due to the relatively integral relationship between the isolating conductive and centering device and the gap structure. In addition, there will be no tendency for the device to move relative to the gap structure once it has been positioned within the housing. These particular modifications also possess the advantages of the previously described devices.

In FIG. 9 a gap structure S5 is shown which comprises a plurality or electrodes 34- having embossed portions S2 and which are separated one from the other by donut shaped resistance spacers 83 which also serve to confine the arc and arc products to the immediate vicinity of the embossed arcing areas.

An elastic member 31 (similar to member 31 of FIG. 2) is positioned immediately atop the uppermost electrode and below the lowermost electrode and a conducting plate 32 is positioned adjacent the opposite face of the elastic member and afiixed to the electrodes 81 to S4 as by a spot weld 86. As in the devices of FiGS. 6-8 the seal is part of the electrode assembly and as such the device has all the advantages of the device of FIGS. 6-8. An additional advantage of the device of FIG. 9 is the fact that with the exception of the elastic member 31' and the conducting plate 32 all standard electrode parts may be utilized without also having to utilize electrode supporting members. This feature greatly reduces the cost of the structure.

While certain modifications differ slightly from other modiiications, all devices described herein are intended to perform the same basic functions: viz,

(l) Provide a relatively air-tight seal between various portions of the interior of a lightning arrester;

y(2) Provide an elastic barrier which serves to center the gap assembly; and,

(3) Provide a means of absorbing transverse and other shock eilects on the arrester which otherwise would inict physical damage on the gap assembly.

While a number of embodiments of the invention have been shown and described, it will be obvious to those skilled in the art, that various changes and modifications can be made therefrom without departing from the invention and, therefore, it is intended for the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

1. An overvoltage protective device comprising an insulating housing having a cylindrical chamber therein, a negative resistance valve block and a plurality of spaced apart electrode members defining a spark gap structure in electrical series relation disposed within said chamber in radially spaced relation to the inner wall of said housing, means including a resilient dise member of greater diameter than said chamber disposed within said chamber between said valve block and said gap structure and deformed against said inner wall of said housing for physically isolating said valve block from said spark gap structure and for sealing between the portions of said chamber containing said valve block and said spark gap structure, whereby ionized gases generated in said spark gap structure cannot drift between said valve block and the walls of said housing and sparkover said valve block, said resilient member having an axial aperture therein, conductive plate members of smaller diameter than said chamber disposed on opposite sides of said resilient member, at least one of said plate members having an axially extending central portion protruding through said aperture in said resilient disc member and being electrically connected to the other conductive plate member, spring means within said chamber for axially urging said valve blocks and said spark gap structure against said plate members, said plate members providing electrical connection between said valve block and said spark gap structure and said resilient member centering said spark gap structure and said valve blocks within said chamber and absorbing transverse shocks to said lightning arrester housing.

2. An overvoltage protective device in accordance with claim l wherein one end of said gap structure is atiixed to one `of said plate members.

3. An overvoltage protective device in accordance with claim l wherein said resilient member is normally of cupshape and of smaller diameter than said chamber and said plate members are urged together by said spring means to flatten said resilient member and deform it against the inner wall of said housing.

4. An overvoltage protective device comprising an insulating housing having a cylindrical chamber therein, a negative resistance valve block and a plurality of spaced apart electrode members deiining a spark gap structure in electrical series relation disposed within said chamber in radially spaced relation to the inner wall of said housing, means including a resilient disc member of greater diameter than said chamber disposed within said chamber between said valve block and said gap structure and deformed against said inner wall of said housing for physically isolating said valve block from said spark gap structurc and for sealing between the portions of said chamber containing said valve block and said spark gap structure, whereby ionized gases generated in said spark gap structure cannot drift between said valve block and the walls of said housing and sparkover said valve block, said resilient member having an axial aperture therein, the electrode member at one end of said spark gap structure being dis posed against one side of said resilient member and having an axially extending portion protruding through said aperture in said resilient member and being afxed to said electrode member at said one end of said gap structure to provide electrical connection between said valve block and said gap structure, said resilient member contering said spark gap structure within said chamber and absorbing transverse shocks to said housing.

5. In a lightning arrester having an insulating housing provided with a cylindrical axial compartment in which a negative resistance valve block and a plurality of disc electrodes deiining a spark gap structure are disposed in radially spaced relation to the inner wall of said housing and spring means directed axially of said compartment resiliently urge said valve block and said gap structure together to maintain them in electrical series relation, a device for physically isolating the portion of said compartment containing said valve biock from the portion thereof containing said spark gap structure while permitting electrical connection therebetween comprising a normally substantially spherical hollow resilient member having opposed apertures therein at its upper and lower ends and normally having a diameter less than that of said compartment and being compressible to a tiattened condition wherein its diameter exceeds that of said compartment and a pair of conducting members each having an axially extending portion disposed in one of said apertures and an annular flat portion extending radially outward therefrom disposed against one end of said resilient member, said device being adapted to be inserted in said compartment between said valve block and said gap structure and flattened by said spring means until said resilient member is deformed in sealing engagement against said inner wall of said housing and said pair of conducting members are in engagement with said valve block and said spark gap structure and are also in engagement with each other within said resilient member to provide an electrical path through said device, said device centering said spark gap structure and said valve block within said compartment and absorbing shocks directed transversely of said housing and conning ionized gases generated between said electrodes to said portion of said compartment containing said spark gap structure.

References Cited by the Examiner UNETED STATES PATENTS 1,763,667 6/3() Mciarlin 315-58 X 2,032,566 3/36 Earle 315-58 X 2,163,697 6/39 Mittelstadt 315-58 2,179,297 ll/39 Johnson 317-70 2,646,096 5/53 Kalb 315--58 X 2,825,008 2/58 Kalb 317-70 GEORGE N. WESTBY, Primary Examiner.

SAMUEL BERNSTEIN, Examiner.

Claims (1)

1. AN OVERVOLTAGE PROTECTIVE DEVICE COMPRISING AN INSULATING HOUSING HAVING A CYLINDRICAL CHAMBER THEREIN, A NEGATIVE RESISTANCE VALVE BLOCK AND A PLURALITY OF SPACED APART ELECTRODE MEMBERS DEFINING A SPARK GAP STRUCTURE IN ELECTRICAL SERIES RELATION DISPOSED WITHIN SAID CHAMBER IN RADIALLY SPACED RELATION TO THE INNER WALL OF SAID HOUSING, MEANS INCLUDING A RESILIENT DISC MEMBER OF GREATER DIAMETER THAN SAID CHAMBER DISPOSED WITHIN SAID CHAMBER BETWEEN SAID VALVE BLOCK AND SAID GAP STRUCTURE AND DEFORMED AGAINST SAID INNER WALL OF SAID HOUSING FOR PHYSICALLY ISOLATING SAID VALVE BLOCK FROM SAID SPARK GAP STRUCTURE AND FOR SEALING BETWEEN THE PORTIONS OF SAID CHAMBER CONTAINING SAID VALVE BLOCK AND SAID SPARK GAP STURCTURE, WHEREBY IONIZED GASES GENERATED IN SAID SPARK GAP STRUCTURE CANNOT DRIFT BETWEEN SAID VALVE BLOCK AND THE WALLS OF SAID HOUSING AND SPARKOVER SAID VALVE BLOCK, SAID RESILIENT MEMBER HAVING AN AXIAL APERTURE THEREIN, CONDUCTIVE PLATE MEMBERS OF SMALLER DIAMETER THAN SAID CHAMBER DISPOSED ON OPPOSITE SIDES OF SAID RESILIENT MEMBER, AT LEAST ONE OF SAID PLATE MEMBERS HAVING AN AXIALLY EXTENDING CENTRAL PORTION PROTRUDING THROUGH SAID APERTURE IN SAID RESILIENT DISC MEMBER AND BEING ELECTRICALLY CONNECTED TO THE OTHER CONDUCTIVE PLATE MEMBER, SPRING MEANS WITHIN SAID CHAMBER FOR AXIALLY URGING SAID VALVE BLOCKS AND SAID SPARK GAP STRUCTURE AGAINST SAID PLATE MEMBERS, SAID PLATE MEMBER PROVIDING ELECTRICAL CONNECTION BETWEEN SAID VALVE BLOCK AND SAID SPARK GAP STRUCTURE AND SAID RESILIENT MEMBER CENTERING SAID SPARK GAP STRUCTURE AND SAID VALVE BLOCK WITHIN SAID CHAMBER AND ABSORBING TRANSVERSE SHOCKS TO SAID LIGHTING ARRESTER HOUSING.

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