US2896116A - Spark gap constructions - Google Patents

Description

July 21, 1959 F. v. CUNNINGHAM SPARK GAP CONSTRUCTIONS Filed April 28. 1958 3 Sheets-Sheet l I mmma INVENTOR. I FRANCJS V. Cunumeu-mm BY Q M A'r'roanav y, 5 F. v. CUNNIN GHAM. 2,896,116

SPARK GAP CONSTRUCTIONS Filed April 28, 1958 s Sheets-Sheet 5 JNVENTOR FRANCE V. CuNNmeHAM ATTORNEY SPARK GAP CONSTRUCI'IONS Francis V. Cunningham, Milwaukee, Wis., assignor-to McGraw-Edison Company, -Milwaukee, Wis., a corporation of Delaware Application April 28, 1958, Serial N0. '731,274

8 Claims. (Cl. 315- 36) This invention relates to spark gap constructions for lightning arresters. i

In greater detail this invention .relates to spark gap constructions for valve type lightning arresters in which what is commonly known as valve typelmaterial is employed and is connectedin series with a spark gap or spark gaps. i

it has been found that approximately a thirty-second of an inch gap is required for each kv. of lightning arrester rating. Thus a three kv. lightning arrester, for example, would require three such gaps connected in series. 7

Greater magnitude of .power follow current could be extinguished if more gaps per kv.,rating were used, but this would result in a higher sparkover voltage and would threfore otter less protection and subject .the protected devices to a greater voltage stress.

This invention is designed to provide atone and the same time a relatively small initial or primary spark gap and to thereafter automatically, due to the inherent'action of the spark gap construction itself as provided by this invention, establish a plurality of secondary or auxialiary spark gaps in series so as to insure the extinguishing of power follow current after the lightning surge has ceased.

In greater detail further objects of this invention are to provide a novel form of spark gap construction for valve type lightning arresters in which the initial gap which normally exists and offers a separation between the power line and the valve material, is a relatively small spark gap to provide a reasonably low sparkover initial action for the spark gap construction, but which as soon as the arcover current is established provides a plurality of spark gaps connected in series with each other so as to insure a quick and certain interruption of the flow of power follow current.

in further detail objects are to provide aspark gap construction in which the surge current flow, whether unidirectional from cloud to earth or earth to cloud or oscillatory, is discharged by a primary spark gap construction and in which the power follow current are is forced into a plurality of gaps formed of spaced metal strips and so arranged that magnetic flux around the current path forces the current flow into a new path farther and farther inwardly of the plurality of spaced metal strips to thereby provide for cooling and deionizing of the follow current. In this way the lightning arrester provides a magnetic flux due to the follow current itself, and in which this magnetic flux tends to shrink in peripheral length, thus crowding the current path farther and farther into a cooler and non-ionized zone farther inwardly of a series of metal strips.

Further objects are to provide a construction in which a U-shaped magnetic member is provided and is positioned around a series of spaced metal strips or plates, and in which an initial spark gap of relatively small arcover characteristics is provided to produce a low nited States Patent t Patented July 21, 1959 '52 initial sparkover and thereafter to produce a series of arc gaps.

Further objects are to provide series spark gap con struction for a valve type lightning arrester which is'so made that either one unit or a plurality of units may be used, and in which a plurality of units may be formed by stacking a series of single units one above the other and positioned in series with the valve material, and in whichleach unit is made in duplicate parts to thereby facilitate the assembly of the metal portions of the spark gap in the individual unit with a minimum of etiort.

Embodiments of the invention are shown in the accompanying drawings in which:

Figure 1 is a view of a lightning arrester with parts broken away and with parts in section.

Figure 2 is an enlarged sectional view through one of theunits of thespark gap. 7

Figure3 is a sectional view on the line 33 of Figure 2.

Figure 4 is asectional view on the line 44 of 'Figure 2.

Figure 5 is a perspectiveview looking into one of the elements of a spark gap unit.

Figure 6 .is a perspective view showing the arrangement of the conducting plates and the magnetizable member of one of the units.

Figure 7 is a sectional view showing a second form of the invention in which a plurality ofstacked units are employed.

Figure 8 is a sectional View showing a third form of the-invention in which -a plurality of stacked units-are employed.

Referring to the drawings particularly Figure 1, it will be seenthat the lightningarrester 1 has a porcelain or other housing 2 and is provided with so-called valve material 3 which may be silicon carbide for instance, and which is interposed between a lower grounded conductor 4 and an upper conducting plate 5, for example as shown in the patent to Ralph H. Earle, 2,296,708, of September 22, 1942, for Circuit-Interrupting Device, and in the patent to the same inventor, Ralph H. Earle, 2,315,320, of March 30, 1943, for Automatic Circuitlnterrupting Device, both of which patents are assigned to the same assignee as the present invention.

This valve material is characterized by the fact that it has a large negative voltage coefficient of resistivity, and is further characterized by the fact that when the current increases the voltage drop across the valve material is less than that which would be directly proportional to the current increase.

Above the conducting upper plate 5 a spark gap unit is positioned and is indicated by the reference character 6, it is connected electrically with the metalplate 5 and with the upper cap or conducting plate 7 which is secured in sealing relation to the porcelain housing 2, a suitable gasket Sbeing interposed. The line conductor 9 is soldered or otherwise secured to the upper cap or plate 7 and a cover of porcelain or other suitable material 10 is provided and plastic or other insulating material 11 is interposed between the plate 7 and the cover 16 as shown inthe Earle patent hereinabove No. 2,315,320.

Theupper metal plate 22 of the upper element 12 of the spark gap-6 is connected to the upper metal plate 7 by means of a flexible conducting woven or otherwise formed metal conducting member 13 which is kept in tight contact with the upper plate 7 and the plate 22 by means of a spring14-in accordance with the'usu'al practice.

The spark gap 6 is composed of the two elements, namely the upper element 12 and the lower element 15. Each of the elements of trunk is provided .with an insulating shell or member 16 formed of suitable non-carbonizing insulating moldable material, such for example as that known to the trade as Mycalex. This casing is provided with a roughly U-shaped upper groove 17 and with a larger lower groove 18 exactly coinciding and shaped in exactly the same manner as the upper groove 17 but preferably deeper than the upper groove. Within these two grooves a magnetizable member 19 is positioned and is in the form of a U as shown. Further it is to be noted that each of the elements which forms a unit of the spark gap as shown in Figure 2, is provided with a series of grooves 20 on its inner side, the longest groove being at the bottom as may be seen from the lower unit 15 in Figures 1 and 2, and the length of the grooves decreasing as the upper or last groove is approached. Within these grooves a plurality of conducting metal plates 21 are positioned and these plates are of gradually decreasing til length as shown in Figures 2 and 7. They are made of a conducting material, such for example as brass, bronze or other suitable material. They may be positioned by slightly springing or bowing them and forcing them into the shell until they snap into the right grooves, or may be otherwise positioned.

The upper conducting plate 22 is positioned above the upper partition 23 which is formed integrally with the side walls of the elements 12 and 15 and which extends only part way across or lengthwise of the unit. The upper metal plate 22 is positioned above the partition 23 and has its end bent around a transverse portion 25 formed integrally with the side wall 16. The inner end of the metal member 22 is wrapped around the bar or member 25 and is indicated by the reference character 26. It will be seen that it has a lower rounded terminal-like portion 27. The lip or upwardly slanting portion 26 of the plate 22 is spaced from the ends of the metal members 21 of the spark gap.

It is to be noted from Figures 2 and 7 that the shell or member 16 has an inwardly projecting lip 27' which bears against the downwardly extending portion 28 of the metal plates 22 and 29.

It is to be noted that the member 19, of magnetic ma terial, is positioned within the two grooves 17 and 18 and serves to align the two elements or sections of the spark gap unit.

In the lower portion of the spark gap unit, namely the portion 15, the same construction of insulator is employed, but it has no metal plates corresponding to the plates 21 in the upper section or element of the unit. The upper conducting plate 29 of the lower element or section 15 has its upper portion spaced below the rounded terminal-like portion 27 of the uppermost conducting plate 22 of the upper section or element.

The lower conducting plate 29 is formed of the same material as remaining plates or metal strips or members 21 and 22, namely of brass, bronze or other suitable conducting material. It is provided with the downwardly extending portion 28 which is held inwardly against the transverse bar or member 25 of the insulating casing or shell 16, as described for the upper conducting plate 22, by means of the inwardly projecting rib 27'. The lower portion of the conducting plate 29 is bent downwardly as indicated at 31 in Figures 2 and 7, and bears against the metal plate 5, see Figure 1, of the lightning arrester, when a single spark gap unit is employed.

The lip 31 of the lowermost plate 29 contacts the metal plate 5, see Figure 1, when a plurality of units of the spark gap are stacked. The material of which the plates are composed is somewhat springy so that the lip 31 is yieldingly held against the next conducting lower member.

If desired, the metal plates 21 and the metal plates 22 and 29 may be held in place during molding of the insulating portions instead of being inserted in grooves after the molding is completed.

:When a lightning surge occurs, Whether oscillatory or unidirectional, from a cloud to the earth, or vice versa, it

will strike across the initial relatively short spark gap formed between the portion 27 of the uppermost plate and the conducting plate 29, see Figure 2. However, as soon as the current flows in this manner it will magnetize the member 19 and the magnetic flux which is in the form of a closed figure, will tend to contract and will force the arc inwardly into engagement with the series of conducting plates 21 so as to form a plurality of individual arcs, and thus serve to interrupt the current flow. It will also be noted that the arc is forced into a non-ionized zone by this magnetic flux, and also it is to be noted that the successive plates act as anodes and cathodes and provide an anode and a cathode voltage drop, which additionally tends to oppose the current flow and thus interrupt the follow-through current.

In the form of the invention shown in Figure 8, the same general type of construction is employed as that shown in Figure 7, with however, the difference that the upper plate 32 of all except the bottom or last element or section is made integral with a solid transverse memher or yoke 33, which is enlarged and presents a slanting surface 34 towards the intermediate disks 35 corresponding to the slanting face of the lip 26 of the construction shown in Figure 7. The bottom or last element or section shown in Figure 8 is identical with the last element or section shown in Figure 7. The lower lip 36 corresponds to the lip 31 of Figure 7, and is integral with the plate 37 of Figure 8.

It is to be understood that when the construction shown in Figure 8 is employed that all of the sections 39 of molded insulating material are altered toaccommodate the enlarged shoulder or marginal member 33, and that the last half section 40 is identical with the last half section shown in Figure 7.

It will be seen that very simple constructions of spark gapsrhave been provided by this invention in which a single unit may be employed or in which a plurality of units may be readily stacked one above the other to provide any desired number of spark gaps.

It is to be noted in all forms of the invention the primary spark gap has its axis and the secondary spark gaps have their axes in approximate alignment. In the forms shown, this line is approximately a vertical line. In addition to this, it is to be noted that the axis of the magnetizable member, or magnetizable members, is substantially vertical and also approximately coincides with the line of the spark gaps hereinabove mentioned. In this way the magnetizable member is magnetized by the arc flowing between the primary spark gap terminals and between the secondary spark gap terminals so that this magnetizable member concentrates the magnetic flux and directs the flux at right angles to the arc and thus causes the arc to travel from the primary spark gap, or primary spark gaps, into the secondary spark gaps and thus serves to extinguish the arc as hereinbefore explained.

It is to be noted that whether a single unit or a plurality of units are employed, the same action takes place, the number of units employed being proportional to the normal voltage of the power line. In every instance a relatively short primary gap is provided so that a reasonably low striking voltage is all that is required. After the arc has been established at the primary gap, the magnetic flux sweeps it over into contact with the ends of the series of metal plates. The are is now broken up into a series of secondary arcs, and the magnetic flux sweeps or forces allof these secondary arcs inwardly of the metal plates so that these multiple secondary arcs are moved into fresh, non-ionized zones and additionally are opposed by anode and cathode voltages, and thus the are due to follow-through current is easily interrupted.

It will be seen that the units may be easily stacked and held in stacked position in perfect alignment, and securely maintained in alignment by means of the U- shaped magnetic members. Further, all of the elements of each unit are duplicates.

While this invention has been primarily described as of use in a valve type lightning arrester it is to be understood that wherever a lightning spark gap is desired this gap construction could be used without departing from the spirit of this invention.

Although the invention has been described in 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.

I claim:

1. A spark gap construction comprising at least one unit having a pair of insulating members arranged to be stacked, each member having a groove aligning with the groove of the other member, a U-shaped magnetizable member seated partially in each groove and holding the units in stacked and aligned relation, said unit having a primary spark gap, and having a plurality of secondary spark gaps, said primary and secondary spark gaps being arranged in an approximate line, said magnetizable member partially surrounding said primary and secondary spark gaps and having an axis approximately aligning with said line and being adapted to be magnetized by current flow across the primary and secondary spark gaps, the magnetic flux from said magnetizable member being arranged to force the arc from the primary spark gap into the secondary spark gaps.

2. A spark gap construction comprising at least one unit having a pair of duplicate insulating members arranged to be stacked, each member having a groove aligning with the groove of the other member, a U-shaped magnetizable member seated partially in each groove and holding the units in stacked and aligned relation, said unit having a primary spark gap, and having a plurality of secondary spark gaps, said primary and secondary spark gaps being arranged in an approximate line, said magnetizable member partially surrounding said primary and secondary spark gaps and having an axis approximately aligning with said line and being adapted to be magnetized by current flow across the primary and secondary spark gaps, the magnetic flux from said magnetizable member being arranged to force the arc from the primary spark gap into the secondary spark gaps.

3. A spark gap construction comprising an insulating shell forming a body portion, a plurality of metal plates arranged in spaced relation within said shell and forming a primary spark gap and a plurality of secondary spark gaps, and a U-shaped magnetizable member having spaced arms embracing and out of contact with said metal plates and magnetizable by current flow across said primary and secondary spark gaps, said primary spark gap being smaller than the sum of a plurality of said secondary spark gaps and having a portion of one of its metal plates located in close proximity to the ends of the metal plates of said secondary spark gaps, whereby an are formed across said primary spark gap will be diverted to said secondary spark gaps by the magnetic flux from said magnetizable member.

4. A spark gap construction comprising an insulating shell forming a body portion, a plurality of metal plates arranged in spaced relation within said shell and having certain of said plates constituting a pair of terminal plates, all of said plates being spaced and the intermediate metal plates having free ends forming secondary spark gaps, one terminal plate having a turned-over portion in close proximity to the other terminal plate and forming therewith a primary spark gap, said turned-over portion having a lip in close proximity to the free ends of said intermediate plates, and a magnetizable member magnetized by current flow across the primary and secondary spark gaps and arranged to force an are from the primary spark gap to the secondary spark gaps.

5. A spark gap construction comprising an insulating shell forming a body portion, a plurality of metal plates arranged in spaced relation within said shell and having certain of said plates constituting a pair of terminal plates, all of said plates being spaced and the intermediate metal plates having free ends forming secondary spark gaps, one terminal plate having a turnedover portion in close proximity to the other terminal plate and forming therewith a primary spark gap, said turned-over portion having a lip in close proximity to the free ends of said intermediate plates, and a magnetizable member magnetized by current flow across the primary and secondary spark gaps and arranged to force an are from the primary spark gap to the secondary spark gaps, and to force said are progressively farther into the space between the intermediate metal plates.

6. A spark gap construction comprising an insulating shell forming a body portion, a plurality of metal plates arranged in spaced relation within said shell and having certain of said plates constituting a pair of terminal plates, all of said plates being spaced and the intermediate metal plates having free ends forming secondary spark gaps, one terminal plate having an end portion in close proximity to the other terminal plate and forming therewith a primary spark gap, said end portion having a face in close proximity to the free ends of said intermediate plates, and a magnetizable member magnetized by current flow across the primary and secondary spark gaps and arranged to force an are from the primary spark gap to the secondary spark gaps, the other terminal plate of said pair of terminal plates having an outwardly extending connecting portion.

7. A spark gap construction for lightning arresters comprising a plurality of stacked units made of insulating non-carbonizing material, each unit having opposed grooves and having outer grooves opening outwardly at the upper and lower sides of each unit, the opposed grooves being in alignment when the units are stacked, a magnetic member positioned partly in each of the opposed grooves of the units and serving to hold the units in alignment and to act as magnetizable members, a plurality of spaced intermediate metal plates positioned within each unit and supported thereby, a plurality of spaced end metal plates supported by each of the units and spaced apart to provide a series of primary spark gaps, the end plate of each unit having a projecting portion overhanging a part of the unit with the projecting portions of successive end plates spaced apart to provide said initial spark gaps, the intermediate plates of each unit forming secondary spark gaps.

8. A spark gap construction comprising an insulating shell forming a body portion, a plurality of metal plates arranged in spaced relation within said shell and having certain of said plates constituting a pair of terminal plates, all of said plates being spaced and the intermediate metal plates having free ends forming secondary spark gaps, one terminal plate having a solid and enlarged end portion in close proximity to the other terminal plate and forming therewith a primary spark gap, said solid and enlarged end portion having a face in close proximity to the free ends of said intermediate plates, and a magnetizable member magnetized by current flow across the primary and secondary spark gaps and arranged to force an arc from the primary spark gap to the secondary spark gaps.

References Cited in the file of this patent UNITED STATES PATENTS 454,672 Thomson June 23, 1891 551,786 Potter Dec. 24, 1895 2,554,278 Teszner May 22, 1951 2,614,232 Kalb Oct. 14, 1952 2,825,008 Kalb Feb. 25, 1958

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