US3379928A - Triggering device for spark generators - Google Patents

Description

April 23, 1968 s. BARBINI TRIGGERING DEVICE FOR SPARK GENERATORS Filed March 8, 1966 3 Sheets-Sheet 1 v ZNVENTOR SPARTACUS BARBINI .A T RNEY April 23, 1968 s. BARBINI 3,379,928

TRIGGERING DEVICE FOR SPARK GENERATORS Filed March 8, 1966 5 Sheets-Sheet 2 FIG. 4 34 FIG. 5

FIG. 6

SPARTAC US BARBINI April 23, 1968 s. BARBINI 3,379,928

TRIGGERING DEVICE FOR SPARK GENERATORS Filed March 8, 1966 5 Sheets-Sheet 8 FIG.7

FIG.8

14 QOOOOOOl IS QOQOOOOOOOO INVENTOR SPARTHCUS B RBINI United States Patent 3,379,928 TRlGGEs NG DEVIQE FOR SPARK GENERATORS Spartacus Barhini, Chenille, France, assignor to Compagnie Generale dElectricite, Paris, France, a corporation of France Filed Mar. 8, 1966, Ser. No. 532,680 Claims priority, application France, Mar. 12, 1965,

a 10 Claims. ci. sis-s7 This invention relates to spark generators including an electric circuit having at least two electrodes and a storage device for electrical energy such as a condenser. More particularly, the invention concerns a novel device for triggering a spark between the electrodes upon the generation in the circuit of a high intensity electric current.

it is known to use triggering devices for high power spark generators comprising an auxiliary or triggering electrode disposed in the gap and connected to a voltage source which is capable of delivering an impulse of sufficiently large amplitude for ionizing the relatively narrow space separating the auxiliary electrode from one of the principal electrodes. Such devices sometimes give rise to dificulties in that the triggering electrode may deflect a part of the principal discharge; such an occurrence is totally contrary to the intended results. On the other hand, the known structures of triggering electrodes and the energy supply device connected therewith may cause problems of insulation due to the large potential differences between the triggering electrode on one hand and the parts of the spark generator on the other hand during triggering and discharge.

The object of the invention is, therefore, to eliminate the disadvantages inherent in spark generators used heretofore wherein auxiliary trig ering electrodes are provided in addition to the principal electrodes.

Another object of the invention is to provide an improved triggering device having a simplified structure that disposes of the necessity of using heavy electrical insulatron.

Still another object of the invention is to provide an improved triggering device that does not need expensive and complicated auxiliary apparatus.

Other objects and advantages of the invention will be better understood from the ensuing specification taken in conjunction with the drawing, wherein:

FIG. 1 is a basic diagram of a spark generator according to the invention;

FIGS. 2, 3, 4 and 5 show four embodiments of a triggering electrode according to the invention;

FIGS. 6 and 7 show modifications of the generator shown in FIG. 1; and

FIG. 8 shows a spark generator particularly adapted for use with the electrode depicted in FIG. 5.

The generator shown in FIG. 1 comprises a condenser 1 connected by means of conductor 2 to an electrode 3 which, together with electrode 4, forms the spark gap per se. Electrode 4 is grounded across a load 5 having a relatively small internal resistance. The spark gap constituted by electrodes 3 and 4 may be surrounded by ambient atmosphere or may be placed in an enclosure formed, for example, by tube 8 which may be transparent and closed at its extremities by means of two terminal walls 99. The structure of electrodes 3 and 4 will become apparent later in connection with the description of FIG. 2, 3, 4 and 5. The enclosure surrounding the electrodes 3 and 4 may be filled with air or gas of high or low pressu e depending upon the requirements regarding the characteristics of the spark.

The apparatus further comprises an electric coil 10 for generating a magnetic field parallel to the axis 3,379,928 Patented Apr. 23, 1968 defined by electrodes 3 and 4. The conductor 6 of the coil 10 is connected to a voltage source 7. This voltage source supplies impulses of very short duration and of relatively high power when energized by an appropriate control device (not shown).

Turning now to FIG. 2, there is shown a first embodiment of an electrode according to the invention. This electrode comprises a generally elongated cylindrical stem 22 having an extended part 21 surrounded by a conductor 24 having a helical shape of varying radius. One end 26 of helix 24 is afiixed -to the stem 22, while the other end 25 is free and is disposed at a short distance from the reduced tip or end portion 23 of extension 21. The helix 24 may comprise either a tubular or a solid conductor and may have a cross-section of any desired configuration. Helix 24 is preferably inscribable in a spherical or ellipsoidal surface. The stem 22 may be filled with a material 28 having good magnetic characteristics such as ferrite or an agglomerated iron powder base. Since stem 22 is placed Within the magnetic field generated by coil 10, the magnetic filling 28 serves to concentrate the magnetic field thus improving the operation of the novel triggering device. Stem 222 is provided with an elongated slot 27 for interrupting the loop formed by the metallic tube and thus preventing the generation of Foucault currents.

The apparatus schematically shown in FIG. 1 and having an electrode 3 of the type shown in FIG. 2 operates in the following manner:

The coil 10 functions as the primary coil of a transformer, the secondary coil of which is constituted by the helicoidal conductor 24. When a voltage impulse is applied to coil 19, a very high voltage is induced in the helicoidal conductor. This voltage produces a spark between the extremities 23 and 25, ionizing the gas sur rounding the spark gap triggering the discharge of condenser 1 across the gap.

One of the principal advantages of the novel triggering device is that the electrode maintains throughout a generally coaxial structure. The helix 24 functions both as an auxiliary triggering electrode and as a principal discharge electrode since the extremities 23 and 25 are both at the same potential at the moment when the main spark is triggered in the generator. Thus, this device is clearly distinguishable from known generators having an auxiliary electrode that is separated and electrically insulated from the principal electrodes. Such auxiliary electrodes may, on the one hand, easily be damaged by the principal discharge of the generator and, on the other hand, may arrest one part of the electric are thus lowering the current passing through load 5.

In the embodiment shown in FIG. 1, the coil 10 constituting the primary coil of the transformer is disposed coaxially with and externally of the electrode assembly.

In the modification shown in FIG. 6 the coil 11 is disposed about the electrode carrying the helicoidal conductor 24.

FIG. 7 shows still a further modification of the generator schematically shown in FIG. 1. According to FIG. 7 the coil 12 functioning as the primary coil of the transrormer is made of a spiral lying in a single plane and embedded in an insulating material of any desired type that also has good mechanical qualities. The flat disc thus obtained may serve as one of the terminal walls of the enclosure surrounding the electrodes constituting the spark gap.

FIG. 3 shows a modification of the embodiment illustrated in FIG. 2. As seen in FIG. 3, the part 21 is embedded in a mass 29 of insulating and heat-resistaing material. This material may preferably consist of fiberglass contained in a synthetic heat hardening material. The mass 29 preferably has a spherical or ovoidal surface of revolution provided with a groove 30 of substantially helicoidal shape. In this groove there is disposed an electric conductor 24, one end 26 of which is afiixed to tube 22, while the other end 25 functions as a triggering electrode disposed adjacent the extremity 23 of part 21. The conductor 24- is preferably made of a copper or bronze band, while the part 21 of the principal electrode may be made entirely or partially of tungsten or tungsten alloy.

FIG. 4 illustrates another embodiment of the novel electrode. The electrode shown in FIG. 4 comprises a cylindrical part 32 similar to stem 22 of FIGS. 2 and 3, an extension 31 forming the principal electrode and a conductor 34 of a spiral configuration lying approximately in a plane perpendicular to members 3132. The end of the external turn of spiral 34 is aflixed by means of a metallic member 36 to the cylindrical part 32, while the end of the turn having the smallest diameter is free and carries a reduced terminus or end portion 35 disposed at a relatively short distance from the end 33 of part 31.

The electrode shown in FIG. 5 is a modification or" that illustrated in FIG. 4. According to the embodiment shown in FIG. 5, the supporting stem is solid and may have any cross-sectional configuration. The spiral is reduced to a single turn 37 having a shape constituting a ring or incomplete annulus and is provided with a gap 38, the edges of which constitute a small auxiliary triggering spark gap. The edge 39 of turn 37 forms the surface where the principal electric spark will be generated.

FIG. 8 schematically shows a generator particularly adapted to electrodes shown in FIG. 5. There is shown a coil 16 embedded in the cylinder 13 forming the lateral wall of the enclosure containing electrodes 14 and 15 that are preferably of the same type. The coil 16 surrounds both electrodes so as to increase the magnetic field to the greatest extent possible and thus compensate for the decrease of the magnetic coupling due to the single spiral of coil 16.

The advantage of the apparatus shown in FIG. 8 resides in that the electric impulse sent through coil 16 will induce the current in the loops of the two electrodes 14 and 15 and will thus increase the efficiency of the triggering of the principal spark.

Although several embodiments of the invention have been depicted and described, it will be apparent that these embodiments are illustrative in nature and that a number of modifications in the apparatus and variations in its end use may be effected without departing from the spirit or scope of the invention as defined in the appended claims.

That which is claimed is:

1. In a spark generator of the type including two electrodes provided with free ends to define a spark gap, the improvement comprising triggering means integral with at least one of said electrodes, said triggering means including an auxiliary spark gap defined by the end portions of two spaced and electrically interconnected conducting parts of said electrode, at least one of said parts forming at least part of a loop, means for generating a magnetic field adapted to pass through said loop for inducing an electromotive force therein to generate an ionizing spark in said auxiliary gap for triggering a spark between said free ends of said electrodes.

2. The improvement as defined in claim 1, wherein said one electrode includes a generally cylindrical metallic tube filled with a ferromagnetic material adapted to concentrate said magnetic field, one of said parts extending from one end of said tube along the axis thereof.

3. The improvement as defined in clairn 1, wherein one of said parts is an elongated, substantially straight member, the end portion of which constitutes said free end, the other of said parts is a helix having a plurality of turns and being disposed coaxially about said member.

4. The improvement as defined in claim 3, wherein said helix is inscribable in at least a portion of a substantially ovoidal surface.

5. The improvement as defined in claim 4, wherein said helix surrounds an electrically insulating and heatresisting ovoidal body provided with a bore through which said straight member extends.

6. The improvement as defined in claim 5, wherein said helix is deposited as a metal layer or band on the surface of said body.

7. The improvement as defined in claim 1, wherein one of said parts is an elongated, substantially straight member, the end portion of which constitutes said free end, the other of said parts is a spiral coaxial with said member and lying in a plane substantially normal thereto.

8. The improvement as defined in claim 1, wherein said parts form a single ring interrupted by said auxiliary gap, one peripheral edge of said ring constituting said free end.

9. The improvement as defined in claim 1 including an elongated enclosure surrounding said electrodes, said means for generating a magnetic field comprises at least one flat coil embedded in a thermosetting material and forming at least one end cap for said, enclosure, one of said parts being an elongated, substantially straight member disposed coaxially with respect to said coil.

10. The improvement as defined in claim 1 including a cylindrical enclosure surrounding said electrodes, said means for generating a magnetic field comprises a helically wound coil disposed about at least one of said electrodes and embedded in said enclosure.

No references cited.

JAMES W. LAWRENCE, Primary Examiner.

P. C. DEMEO, Assistant Examiner.

Claims (1)

1. IN A SPARK GENERATOR OF THE TYPE INCLUDING TWO ELECTRODES PROVIDED WITH FREE ENDS TO DEFINE A SPARK GAP, THE IMPROVEMENT COMPRISING TRIGGERING MEANS INTEGRAL WITH AT LEAST ONE OF SAID ELECTRODES, SAID TRIGGERING MEANS INCLUDING AN AUXILIARY SPARK GAP DEFINED BY THE END PORTIONS OF TWO SPACED AND ELECTRICALLY INTERCONNECTED CONDUCTING PARTS OF SAID ELECTRODE, AT LEAST ONE OF SAID PARTS FORMING AT LEAST PART OF A LOOP, MEANS FOR GENERATING A MAGNETIC FIELD ADAPTED TO PASS THROUGH SAID LOOP FOR INDUCING AN ELECTROMOTIVE FORCE THEREIN TO GENERATE AN IONIZING SPARK IN SAID AUXILIARY GAP FOR TRIGGERING A SPARK BETWEEN SAID FREE ENDS OF SAID ELECTRODES.

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