US2032566A - Lightning arrester - Google Patents

Description

March 3, 1936. R H, EARLE 2,032,566

LIGHTNING ARRESTER Filed March 24, 1935 ww@ /7 zu INVENTOR ATTOR Y Patented Mar. 3, 1936 UNITED STATES PATENT GFFICE LIGHTNING ARRESTER Application March 24, 1933, Serial No. 662,443

6 Claims.

This invention relates to lightning arresters.

Objects of this invention are to provide a novel form of spark gap in a lightning arrester which cooperates with a granular mass of material, such as silicon carbide, which is a self-contained, unitary, rigid structure, which may be employed to transmit pressure to the granular material, and which may be assembled in the arrester as a unit. j

Further objects are to provide a spark gap construction for a lightning arrester which can be calibrated independently of the arrester, which has practically no leakage, which avoids radio interference, and which has substantially no corona formation.

Fiuther objects are to provide a spark gap for a lightning arrester which is practically lnstantaneous in operation, which is substantially unaifected by successive discharges and has a very long life, in which a construction is provided where individual, relatively heavy units are employed and form-jointly the spark gap, each unit being of suicient mass to prevent any excessive heating, although large discharges may occur, and which will not pit nor noticeably deteriorate, even after a long active period of service.

In greater detail, objects of this invention are to provide a spark gap construction for a. lightning arrester in which ceramic spacers are accurately machined and receive between them relatively large, heavy metal cylindrical members, also accurately machined and preferably polished, so that the metal members are held in a definite spacing, such members being so formed as to provide a path for the arc away from the ceramic spacers, and in which upper and lower electrodes or transverse plates are locked to the assembly so as to hold the entire device together as a single rigid unitary structure.

Embodiments of the invention are shown in the accompanying drawing, in which:-

Figure 1 is a side elevation partly broken away and partly in section, showing the lightning arrester equipped with the spark gap.

Figure 2 is an enlarged sectional view on the line 2-2 of Figure 1.

Figure 3 is a view corresponding to Figure 2, showing a modiied form of the invention.

Referring to Figures 1 and 2, it will be seen that the arrester comprises a porcelain housing I which is partially iilled with granular material 2, such as silicon carbide, and which is provided with a lower plate l and an upper plate 4 at opposite ends of the crystalline or granular mass.

The lower plate is sealed in place by means of a soft metal seal 5 bonding the stranded portions of the ground conductor 6 to the metal plate and also accurately conforming to the interior contour of the housing I, a rubber annular, double wedge-shaped gasket l being provided and being spaced from the granular material.

The lower portion of the arrester is completed by providing an asphalt seal 8 and a sulphur compound seal 9, although one or the other or both of these seals may be employed, as desired.

The general details of this arrester are more fully set forth in my copending application S. N. 658,714, filed Feb. 27, 1933, this application being directed primarily to the spark gap per se.

The upper plate 4 has soft metal I0 molded in place. Preferably the soft metal ID is type metal and shrinks slightly so as to provide a plunger accurately fitting the interior contour of the housing.

The upper end of the housing is closed by a springy copper cap II which has downwardly turned anges overhanging the upper edge of the housing. These anges have type metal or other soft metal I2 poured into place and molded, as shown, in interlocking relation with the housing so as to hold the metal cap under tension and thereby transmit tension downwardly through the spark gap hereinaftery described to the granular material.

The device may be covered by a porcelain cap I3 and an asphalt cement I4 may be poured between the flanges of the porcelain cap and the body portion.

It is to be noted that the line conductor or high tension conductor I5 is bonded in place to the metal cap by the soft metal seal.

It is preferable to slightly bevel the upper edge of the housing and to provide a rubber or other yielding gasket I6 at this point. It is to be noted that both the gaskets 'I and I6 are double wedgeshaped, as described in greater detail in my copending application noted above.

The spark gap assembly comprises a pair of insulating uprights Il formed of ceramic material, such as ceramic porcelain of a very high insulating characteristic. These uprights are drilled, as indicated at I8, see the broken away portion of the uprights shown in Figure 1, to receive the trunnlons I9 of a plurality of cylindrical metal members 20, 2|, 22 and 23.

These metal members forming the individual elements of the spark gap are preferably of a high grade brass and are relatively large and turned down, preferably to provide the integral trunnlons I9 and tapered side portions with the major body portion of a cylindrical contour. These individual members forming the spark gap are accurately machined and are preferably polished. The uppermost and lowermost of these members, indicated by the reference characters 2d and 23, respectively, are provided with a tapped hole which receives fastening screws hereinafter described.

An upper plate or transverse metal strap member 2li is provided 'with downwardly turned flanges 25 which fit outside of the uprights and thus hold the upper ends against separation. A round headed screw 26 passes through the strap member 2d and is screwed into the upper member 20, a metal spacer Z'l'being provided, if desired.

The lower portion of the spark gap is provided with a transverse strap metal member or plate 28 formed similarly to the upper plate 2li and provided with upturned flanges 29 located outside of the uprlghts il. A screw 3@ extends through this plate and is screwed into the lower member 23 of the spark gap, as shown most clearly in Figure l. This screw is preferably a tapered head or countersunk type screw and may or may not extend through the plate G, as desired. In the form shown the screw il@ has been shown as extending through the plat/e 1, although obviously it may extend only through the transverse member 28, if desired, as the plate il is securely bonded to the transverse plate or strap metal member 25 by the soft metal lil which is molded in place, as described hereinabove.

Referring in greater detail to the spark gap,

it will be seen from Figure 2 that the successive members 2u, 2l, 22 and 23 are spaced apart different distances in the rst form of the inven` tion and may be of the same size. It is obvious that the invention in its broader aspects compre'- hends the equal spacing of the same or of diderent sizes of members or elements.

As shown in Figure 2, the upper spacing is the greatest, that is to say the space between the members 2li and 2l is the greatest spacing. The spacing between the members 2l and 22 is the lesser spacing, and the spacing between .the members 22 and 23 is the smallest spacing. In other words, the spacmg successively decreases from the live member il@ to the bottom member 23, no matter how many members are employed, four being shown although obviously another number could be employed.

In the form of the invention shown in Figure 3, the same idea as that previously described is followed, except that the uppermost member 3Q is the smallest member and the lower member 23' i's the largest member, the members 2li and 22' being uniformly graduated in size, as illustrated in Figure 3. Otherwise this construction is the same as that shown in Figure 2. This form of the spark gap, therefore, provides a series of members increasing in size from the live uppermost memberto the lowermcist member, which is electrically connected, as previously indicated, to the granular material.

It is within the scope of this invention to have uniform spacing for either the varying sized members or for the uniform sized members, although the construction described and shown is the preferred form.

In each form of the invention the round headed upper screw 2b serves an important purpose in addition to that described. It ts within a recess formed in the spring metal cap il so that when the mp is tensioned or pressed downwardly and locked to the housing, as described in greater detail in my copending application noted above, pressure is transmitted through the spark gap to the granular material, and, in addition, the upper end of the spark gap is accurately centered 5 without requiring perforating of the metal cap.

The spark gaps provided by this invention furnish a very large mass for each individual element and consequently although severe discharges may take place, there will be no over- 10 heating, burning or pitting.

Further than this, it is to be noted that the tapered end portions of these individual members diverge or extend away from each other and consequently the path of the arc is confined to the 15 central portion of the structure and is kept away from the ceramic uprights. Further it will be noted that there is a minimum chance for leakage or radio interference.

In addition to this, it has been found from actual tests that the spark gap is substantially instantaneous in operation and that it rapidly extinguishes the are. Although the exact theory may not be at present fully known, it has been found that the unequal spacing of the successive 25 members with thev greatest space below the live member and the minimum space at the other end of the structure, produces the best results. There is substantially no corona formation with this type of spark gap, as there are no sharp edges 30- presented. Also the spark gap has a very long life as distinguished from relatively light material sheet metal spark gaps.

The tendency to interrupt the arc occurs at each of the spacings, as is obvious, and consequently the arc is very quickly suppressed after the discharge has taken place and there is practically no follow-through current from the line.

Another point to be noted is that any expansion of the metal members does not cause elongation of the spark gap, as each member is free to expand independently of the other members.

It has been found from actual practice that the ceramic supporting members may be accurately machined to very accurately position and space the respective members, and that also this selfcontained rigid unitary spark gap may be handled as a separatestructure in assembling the lightning arrester and consequently materially facilitates the manufacture thereof.

Another very important result of this construction is that the spark gap may be separately calibrated, that is separately from the remainder of the lightning arrester. It has been found that these spark gaps are remarkably uniform and readily lend themselves to quantity production.

While the drawing illustrates the spacing between successive members forming the gap as approximately uniformly graduated, that is to say, uniformly decreasing from one end to the other of the spark gap, it is to be distinctly understood that the graduation in spacing need not be uniform, and that the spacing itself need not be uniform. It is obvious within the province of this invention to combine the uniformly gradu- 65 ated spacing with a portion having uniform spacing, if it is so desired. The uniform spacing is shown in my'copending application Serial No. 658,714, led February 27, 1933.

Although this invention has been described in 70 considerable detail, it is to be understood that such description is intended as illustrative rather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

li claim:

I. A spark gap for a lightning arrester comprising a pair of ceramic supports and a plurality of cylindrical members supported between said uprights and formed of metal and having tapered end portions adjacent said supports.

2. A spark gap ior a lightning arrester consist'- ing of a pair of insulating uprights held together by upper and lower conducting members, and a plurality of individual and separate metal'members of approximately cylindrical contour mounted between said uprights and held in spaced relation to each other, and securing means extending between the upper and lower conducting members and engaging the upper and lower metal members of the spark gap respectively.

3. A spark gap for a lightning arrester comprising a unitary, rigid, self-contained structure including a pair oi insulating uprights having spaced holes therein, substantially cylindrical metal membersmounted between said uprights and having trunnions extending into the holes of said uprights, and upper and lower conducting members overlapping said uprights and holding said uprights against spreading.

4. A spark gap for a lightning arrester comprising a pair of spaced insulating members having holes therethrough, a plurality oi substantially cylindrical metal members -positioned between said insulating members and having integral portions projecting into the holes in said insulating members, strap metal members having Vinwardly' turned iianges located at opposite ends of said insulating members and having the flanges located outside oi said insulating members, and screws passing through the strap metal members and engaging the adjacent substantially cylindrical members of said spark gap.

5. A spark gap for a lightning arrester comprising a plurality of spaced metal members, insulating means for supporting said metal members, the spacing between members being greater at one end-and successively decreasing towards the other end, and the size of the member adjacent the first mentioned end being smallest, the size of the members increasing towards the last Vmentioned end, the smallest of said members being adapted for connection to a high tension line.

6. A spark gap for a lightning arrester comprising a plurality of spaced metal members, insulating means for supporting said metalA members, the spacing between members being greater at one end and successively decreasing towards thel tions and having their axes parallel.

RALPH H. EARLE.

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