US1955520A - Electrical discharge device - Google Patents

Description

April 17, 1934.

C. E. VAWTER Filed Nov. 20, 1930 3 Sheets-Sheet l I INVENTOR CE. I/awTer BY ATTORNEY April 17, 1934. c. E. vAwTER ELECTRICAL DISCHARGE DEVICE Filed Nov. 20, 1930 3 Sheets-Sheet 2 INVENTOR Gil a Wfer BY ATTORNEY April 17, 1934.

c. E. VAWTER 1,955,520 ELECTRICAL DISCHARGE DEVICE Filed Nov. 20, 1930 3 Sheets-Sheet 3 7 74 fi L i;

INVENTOR 0E. Vawfer BYZ' Z ATTORN EY Patent ed Apr. 17, 1934 ELECTRICAL DISCHARGE DEVICE Charles E. Vawter, Philadelphia, ra; Germantown Trust Company executor of said Charles E. Vawter, deceased Application November 20, 1930, Serial No. 496,999

18 Claims.

My invention relates to apparatus for and methods of producing, electrical discharges and arcs and more particularly relates to improved apparatus for and methods of establishing arcs S-Irom low voltage sources.

In many operations requiring heat, such'as welding, ignition of oil in oil burners, etc., it is desirable to use" electrical heat producing means. It is important, in these cases, to provide a maxilO mum amount of heat for efllcient operation.

Usually, however, for practical reasons and for safety, only the normal voltages used for household purposes are available and provision must accordingly be made to produce the necessary heat energy from a comparatively low voltage such as 110 volts source. 7

Two well-known forms of heat into which electricity can be translated are the spark and the arc.

A spark is a disruptive discharge of sufllciently high voltage to break down the gas in the gap between two electrodes without previous ionization of the gas and consequent reduction of the resistance of the gap.

:3 An arc discharge, on the other hand, takes place only after the resistance of the gap has been diminished by the ionization of thematerial between the electrodes. Thus, for example, it requires thousands of volts toproduce a disrup- 33 tive discharge between the spaced electrodes, but when: the gap is once bridged by such a discharge, the resistance 01 the gap is so reduced by-the ionization'of the gas that it requires a relatively low voltage to maintain an arc discharge be- 35 tween the electrodes.'

Heretofore, as for example in oil burner ignition, transformers have been used with three amperes at 110 volts on the primary and twentyfive milliamperes at 10,000 volts for the spark ignition currents from the secondary.

Twenty-five milliamperes, however, does not provide sufficient heat to efficiently ignite the oil. It is, accordingly, necessary to increase the A5 voltage across the secondary of the transformer to obtain the current necessary to produce the desired heat. I

For example, to produce a minimum current required, such as a quarter of an ampere, would requ're 100,000 volts in the above described transformer system. Sucha voltage would re.

quire insulation entirely too bulky and expensive for practical use.

By converting a disruptive spark discharge into an arc discharge, however, the low voltage requires less mechanical parts.

current passing between the electrodes can be increased enormously.

Accordingly, the principle of ionizing the gas in a gap between electrodes by a high voltage spark discharge to be followed by a low voltage arc, has been tried. This has been accomplished by the provision of an interrupter in parallel with an arc gap, by means of which a high fre- ,quency current is generated to ionize the gap .contacts as well as the gap between the electrodes and, these two gaps being in parallel, the,

arc is sometimes established across one gap and sometimes across the other. The system is therefore, not only rendered inoperative, but the formation of an arc at the interrupter contacts quickly destroys these contacts.

It is, accordingly, an object of my invention to provide a novel high frequency spark and are discharge system and a novel method of producing the same, such that the'arc is made to occur with certainty across the 'arc electrodes and it is impossible to maintain an arc across the interrupter contacts.

In order to overcome this difficulty, it has been 35 proposed in my copending application, Serial No.

4433130, filed April 12, 1930, of which this application is a continuation in part, to provide a continually operating interrupter mounted on a rotating member. Such an interrupter, while feasig0 ble for the specific illustration of the invention, disclosed in that application to an ignition system for internal combustion engines, due to the fact that there are rotating members already available on such engines which can be utilized. for interrupting purposes, it isnot practical in instances where rotating members are not available, such for example, as in the art of arc welding, igniting fluids, etc. In the latter cases, the rotating member would render the device very 10b costly and impractical due to the complications which accompany the additional moving parts I have discovered that, inasmuch as according to the'methods and apparatus for establishing arcs which I have invented, a single operation of the starting contact may be suflicient to start the discharge, electromagnetic control of the interrupter contacts is more efflcient and cheaper and An electromaga net can also quickly re-establish the areifbroken,

thus further reducing the danger of breakdown.

Accordingly, a further object of my invention is to provide novel apparatus for and methods of establishing and maintaining an are by means of an electromagnetically operated interrupter contact in combination with means for insuring the establishing of an are at the electrodes and preventing the are from forming at the interrupter contacts.

A further serious and heretofore insurmountable disadvantage of arc discharge ignition systems has been that the extremely high frequency current employed to produce the disruptive discharge sooner or later caused a breakdown of the condensers employed in this system. Although thismight not occur immediately, it, seemed to invariably occur after the system had been in operation for some short time. Heretofore, this difliculty has been overcome by constructing the condenser of expensive material which has rendered the arc discharge system commercially impracticable.

Accordingly, a still further object of my invention is to provide a novel are discharge system in which the circuit is so arranged that the breakdown of the relatively inexpensive condensers, used in the system, is avoided.

Moreover, in the arc ignition system that has been previously proposed, the arcing current which is of comparatively high value is passed through the secondary of a high frequency transformer employed to produce a disruptive discharge. This necessitated the use of excessively large wire in the secondary which is undesirable for a number of reasons, among them being the cost and the large distributed capacity of the secondary winding. The greatest difflculty with passing the arc and current through the secondary, however, is that the heating effect of this current in the secondary causes an increase in the dielectric losses of the transformer and thereby reduces the high frequency ionizing or disruptive discharge current.

Accordingly, a further object of my invention is to arrange the circuit of a magnet controlled vibrator arcing system so that the arcing current is prevented from passing through the secondary winding of the transformer.

Considerable difficulties have been experienced with the ignition system in oil burners. If an insufficiently hot igniting flame is obtained, unbumt oil is permitted to accumulate, causing eventual failure of ignition and occasionally an explosion with disastrous effects may occur. It is well known that this diiflculty in oil burners has seriously retarded its development.

The failure of oil to ignite is, as is well understood, due to the fact that the temperature of the igniting flame is below the flash point of the oil, or even that the electrodes between which ignition is obtained is short circuited due to the accumulations of carbon from the oil on the electrodes.

Furthermore, moisture collecting on the insulation separating the electrodes will short circuit the high voltage spark ignition.

Accordingly, still a further-object of my invention is to provide novel means for igniting low grade oils having a higher flash point.

Another object of my invention is to provide novel means for automatically burning up any carbon which may accumulate'on'the arcing electrodes.

Still a further object of my invention is to provide novel means whereby accumulations of carbon on the electrodes aids arcing and protects the electrodes.

A further object of my invention is to provide novel means whereby moisture does not affect the arcing.

Another object of my invention is to provide means whereby arcing at the electrodes may be produced from a source of alternating current or direct current.

Similar circuit combinations are particularly well adapted for utilizing with arc welding ap paratus. It is well known that in arc welding, particularly when the currents are of relatively small magnitude, for'instance 30'amperes or less, difliculties in maintaining a continuous arc during the welding process without having to strike the are at indefinite and frequent intervals have been experienced. By utilizing my circuit for striking the arc automatically whenever it is interrupted, I am enabled to have a system of welding wherein the welding process can be carried on continuously and without interruption and with automatic means for establishing and maintaining the welding arc.

Thus, a further object of my invention is to provide novel apparatus for and methods of producing an electric are for welding purposes.

Still further objects and uses of my invention are for the purpose of starting mercury arcs, fluid ignition, etc.

Other objects of my invention are such as will be clear from the detailed description of the invention which is to follow, in which:

Figure 1 is a schematic circuit diagram of my improved lgnition'system.

Figure 2 is a similar diagram containing certai... modifications.

Figure 3 is a diagrammatic illustration of the application of my invention for arc welding.

Figure 4 is a similar illustration of the application of my invention for butt welding.

Figure 5 is a diagrammatic illustration of a modification of the application of my invention for welding purposes.

Figure 6 is a diagrammatic illustration of a still further application of my invention for the splicing of wires; and 4 Figure 7 is a diagrammatic illustration of my invention adapted for igniting oil, gas, or other combustible fluids.

V Figure 8 schematically shows a mercury arc rectifier.

Referring first to Figure 1, the source of electrical energy 1 may be either direct or alternatin current and preferably of 110 volts, although as low as 60 volts may be used. 7

The supply source may consist of either a battery 2 or a generator 3. One terminal of the source energy 1 is connected to the common return conductor 4 and the other terminal is connected by the lead 5 to the control switch 6, which is shunted by the condenser '7. The condenser is connected across the make and break contact 6 to prevent arcing thereat. This circuit is completed over a variable resistance 8, contactor 9, winding of the relay 10, conductor 11, the primary winding 12 of the transformer 13, through the contacts is and the armature 15' controlled by the relay 10, conductor 15, and resistance 16, back to the common conductor 4.

In this circuit, the resistance 8 is inserted in order to control the amplitude of the current which flows thereover. The relay 10 is energized by current which flows in this circuit to attract its associated armature 1-5' which disengages the contact 14.

' The transformer 13 is a high frequency transformer and therefore preferably has an air core. The primary winding 12 consists of relatively few turns of heavy wire so that its resistance is prac-- tically negligible.

A condenser 18 is connected between the interrupter 14 and the conductor 11- across the terminals of the primary winding 12, forming therewith an oscillating circuit which is controlled by the interrupter 14. The capacity and inductive reactances are such that the natural frequency of the circuit is extremely high, although preferably below the radio broadcasting range of frequencies, so that the apparatus will not interfere with radio reception.

Between one end of the primary winding 12 and the secondary winding 17 of the transformer 13, is connected an inductance 21 which excludes from the primary circuit all high voltage, high frequency currents from the secondary 17 which would otherwise pass directly across the common terminals of windings 17 and 12.

The lead 4 may be grounded whendes'ired, as for instance for welding apparatus or if it appears'to be safer to do so, both terminals inay be left ungrounded, in which case the transmission of high frequency disturbance to the supply line is sometimes reduced.

It will be understood that the inductance 21,

as well as. the inductance of the relay 10. are

wound with sufllciently heavy wire and are otherwise of appropriate construction for carrying the arc current from supply source 1 which will vary, depending upon the heating properties of the arc discharge desired for' any particular purpose. The ohmic resistance of inductance 21 and also of the relay winding 10 are as low as possible so v as to .avoid overheating and to provide a more direct path for the arcing current over the arc gaps rather than through resistance 16, as will be explained more fully hereinafter. The secondary 17 of the transformer 13 is connected in series with a condenser 23 which is connected over conductor 24 to one terminal of the arc discharge 25, the other terminal of which is connected to the opposite terminal of the second- I ary winding 17 of transformer is. Conductor 24 is also connected to the common return conductor 4.

In operation, the switch 6 is a manually operated switch mechanically designed to remain closed as long as it is desired to operate the arc system. For. operation, the contact 6 is closed,

completing the circuit for the relay 10, described above. Relay 10 is energized and operates its armature 15 to disengage the contacts 14.

The current flowing over this circuit also results in the storing of a considerable amount of.

electromagnetic and electrostatic energy in the primary circuit, including the primary winding 12 of the transformer 13 and condenser 18.

When the interrupter contact 14 is opened as a result of the energization of relay 10, a spark is produced thereacross due'to the high in'ductance of windings 10 and 12 in the circuit, As a result, high frequency oscillations are produced in the circuit including the' condenser 18 and the inductance 12, similar to the phenomena of a spark oscillator used in radio sets. Although this energy dissipates itself in a minutely short period of time, the oscillations are, while in operation, ofv a very high frequency, determined, 01 course, by the constants of the oscillating circuit traced above and which, as stated hereinbefore, has a very high natural frequency.

D'uring these oscillations, a high frequency voltage is generated in the secondary 17, the voltage induced in the secondary being higher than in the primary,inasmuch as this is a stepup transformer. As this transformer is for the purpose, of stepping up high frequency voltages, the step-up action is not necessarily due to the increased number of turns. Such step-up in voltage in oscillating circuits can always be se cured by a'proper choice of capacity and inductance constants in the primary and secondary circuit, and these should be arranged in combination with the ratio of turns of the windings, to give the necessary step-up voltage relation for the range of inherent capacities of the parts connected to the spark gap. As the energy dies out in the primary circuit, it builds up in the secondary circuit until a voltage is built up in the secondary circuit sufliciently high to jump of the gap to a sufilciently low value so that the potential from the supply source 1 is sufiicient to cause the current from this source to flow through the primary circuit from relay 10 by way of conductor 11 through the winding 21 and across the gap 25. The disruptive discharge which takes place first and bridges the gap 25 is thereby converted into an arc discharge.

The small current produced by the oscillatory spark discharge which bridges the gap 25 and which has a correspondingly small heating value isv thus suddenly transformed into a current which may be 100 or more times larger-say of the order of l ampere-and which is sufficient to produce an arc of intense heat. The intensity of this are is, moreover, sufficient for igniting low grade oils and other fuels When this system is employed for arc welding purposes, the operating current is, of course, even larger than one ampere and such a current will be obtained in the circuit by the proper choice of the values of resistance 8 and the resistance of the winding 10 and 21 through which this current will drawn between the interrupter contacts 14 whenever discharge takes place across the gap 25. The interrupter contacts 14 and the electrodes of gap 25 are connected in parallel with the source 1. Hence, normally if an arc is established across the gap 25, it will not be maintained across the contacts 14, and if an arc is maintained across the contacts 14, it will not be established across the gap 25.

By placing the resistance 16 in series with the interrupter contact 14, however, and choosing a value of this resistance which is large in comparison with the resistance of the winding 21, the

The inductance of the relay 10, in addition to current from the source 2, which chooses the path of least resistance flows through the coil 21 and the ionized gap 25, so that the arc is prevented from being maintained across interrupter 14 and will be established across the gap.

If for any reason, the arc, after it has been established, is extinguished while switch 6 is closed, the circuit for electro-magnet 10 is opened at both its own armature 15', which is then in its energized position disengaging contact 14 and also at gap 25. The electromagnet will therefore deenergize and armature 15 will engage contact 14. Thereupon, electromagnet 10 will again be energized over the circuit described in the above and the operations for producing an are at gap 25 repeated. An automatic restarting arc is thus produced.

Referring now to Figure 2 of the accompanying drawings, the modified circuits here shown are identical with the circuits of Figure 1, except for the omission of 'the impedance 21 between the primary and secondary windings 12 and, 1'7, and the insertion of a discharge condenser "31 connected between the secondary 1'7 and the common return conductor 4, and which functions in the manner described in connection with condenser 23 in Figure 1 to produce an oscillatory' circuit with the secondary winding 17 and the arc electrodes 25. With this arrangement, however, the arcing current flows through winding 1'7 and, accordingly the resistance of winding 1'7 must be made relatively small. Also to prevent arcing at contacts 14, the resistance of 16 must be made large with respect to the ohmic resistance of the secondary 1'7, in order to provide a path of least resistance through the secondary 1'7 to gap 25 for the arcing currents.

In Figure 3, I have shown one specific adaptation of my invention to arc welding. As shown in this figure, the terminals 35 and 36 are the terminals which would be connected to the leads extending to the gap terminals in Figures 1 and 2. In practice, 35 extends to the high tension terminal 25 and 36 to the grounded terminal. Terminal 35 is mounted on the flexible highly insulated cable 37. This cable 37 is carried by an insulator handle 38 which is heat insulated by means of asbestos shield 39 rigidly secured between the'handle 38 and a holder 40. Holder 40 is provided at one end thereof with an aperture in which is slidably mounted an electrode 41 of carbon welding metal, or any desired material and which may be adjusted longitudinally in the slot by means of a set screw 42 which screws into the end of the holder40 and engages the electrode 41.

The second terminal 36 is connected to one end of a conductor 43, the other end of which is connected to two work members 44 and 45 which are the pieces to be welded together and which act as the second electrode. These members may be held together and to the conductor 43 in any desired manner.

In operation, the arc is struck by bringing electrode 41 up to the required distance from the joint of 44 and 45 when the are jumps and'is maintained. The intensity of the arc can be controlled by resistance 8, by means of the slideable contact 9, Figures 1 and 2, or by the length of the arc gap. The are, thus struck as described in connection with Figures 1 and 2, then welds the joint.

In Figure 4, an arrangement for butt welding is shown. In this figure, the terminal 4'7, connected to the conductors extending to the high tension terminal of the gap in Figure 1, is mounted on the high insulator 48 which, in turn, is carried by the supporting metal member 49. An aperture near the top of support '49 carries one of the work members 52 adjustable in a horizontal plane. A set screw engages and secures the work member 52 in position. The member 55, to be butt welded, is horizontally and slidably mounted in an aperture in upright metal member 56 and is held securely in position by set screw 57. The upright metal member 56 is mounted on the sleeve 58 which is slideably mounted on the carrier table 59 and is moved by means of a rotating worm screw 61 with which an extension 58 of the sleeve meshes.

The end of the upright member 49 screws into an insulator member 62 which is supported on the carrier 59 and insulates it from the member 49. A set screw 63 secures the insulator 62 to the carrier 59. The carrier 59 at one end is connected over the conductor 65 to the grounded terminal 66 of the gap. A spark gap between terminals 6'7 and 68 is provided to protect the system from strain when the electrodes are initially separated.

As the worm 61 is driven by any well known means, as for example a motor, the member 55 is brought towards member 52 at a proper speed. At a certain predetermined distance, depending upon the design of the arc starting system and the electrodes, an arc is produced. This are continues until the ends are brought in contact and fused together to form a butt welded joint. The speed at which this operation takes place most satisfactorily is determined by experience and is very important.

In Figure 5, a further modification of my invention for welding purposes is disclosed, in which a highly insulated member '71 is connected to the high tension electrode terminal as in Figure 4, and a conductor '72 is connected to the grounded terminal. These members are carried through the insulator member '73 and asbestos shield '74, which in turn carries the electrodes '76 and 7'7 and the extension '78 having an orifice '78. A hydrogen tank in a known manner is connected by a flexible hose 83 through members '73 and '78 to produce a flow of gas between electrodes '76 and '77. When an arc is produced between these electrodes in the manner described above, the hydrogen is permitted to flow through orifice 78 and, as it ignites, produces a high temperature for metal cutting.

is illustrated. Two wires, '71 and '72, are brought a in abutment with each other, as shown, through the opening '73 of two engaging halves of a member '74 of heat resisting material. The wires are inserted through the opening '73 and brought in juxtaposition with each other.

Heretofore, as the wires are brought together and the are started, the heat caused by the arc tends to cause the ends to butt weld and the welding results in a hump at the welding point. In accordance with the present invention, the container '74, because it has a very low coefficient of expansion, acts as a mold to maintain the normal cross section of the wires constant as they are welded.

In Figure '7, I have diagrammatically illustrated and electrically connected to the screw 83. The .opposite electrode 87 is grounded. The unit is held in place by the two shoulders 82 and 86.

In Figure 8, the application of the device, to a mercury switch 88 is shown. The mercury pool 89, electrodes 90 and 91, are all commonly known in mercury switches. Electrodes 92 and 93 are the two electrodes of my arcing devices and functionto ignite the mercury vapor when a dis charge is produced across electrodes 92 and 93 in' the manner shown in Figures 1 and 2.

It will be obvious, from the above description,

that my invention has other adaptations, as for example, starting the arc in mercury arc lamps.

By extending the terminals of the gap to the terminal points in the arc lamp, an arc discharge may be induced in the lamp which will volatilize in which the walls of the furnace are diagrammatically illustrated at 81. Projecting through an opening there is a unit 82 comprising any'desired form of arcing device, such as illustrated.

Inthe device, shown for illustration/the high voltage terminalof the arcing electrodes 25 of either Figures 1 or 2, is connected through the top screw 83 to the central electrode 84 which extends through the body of insulating material 85.

,Connection to the other branch of the circuit is made by means of the fastening of the main portion of the shell to ,thegrounded sideof the system through the screw thread. 86 to which is connected the second electrode 87. Electrode 87 is usually permanently adjusted and shaped relative to electrode 84, so that for a short distance the electrodes are nearly parallel for increasing their life.

connection with oil burners.

Although I have illustrated a form of my in- .vention forigniting oil burners, it will be understood that this showing is diagrammatic and any other form may be used. Furthermore, any well known form of temperature control may be used in conjunction with my system.

I donot wish to limit my invention to the speciflc illustrations thereof herein given, except insofar as set forth in the following claims, in

- which I claim as my invention:

1. it discharge system comprising a primary circuit containing a transformer primary and a relay controlled circuit interrupter, a secondary circuit containing a transformer secondary and a gap, means for establishing current from the primary circuit across said gap when the same has been bridged by the secondary volt'age and resistance means for preventing the current of the primary circuit from maintaining an arc discharge a'cross'the interrupter contacts.

2. A discharge system comprising a primary' circuit containing a transformer primary, a relay connected in series with said transformer primary, a circuit interrupter, an oscillatingclrcuit comprising a condenser, said transformer primary, a secondary circuit containing a transformer secondary and a gap,'m'eans whereby the current of the primary circuit is established across the gap when the same has been bridged by the secondary voltage and'resistance means for.

preventing the primary current from maintaining an arc discharge across the interrupter contacts.

3. A discharge system comprising a primary circuit containing a transformer primary and an electromagnetically controlled circuit interrupter having an actuating coil connected in-the primary circuit, an oscillating circuit consisting of a condenser, said transformer primary, a secondary circuit containing a transformer secondary and a gap, a common supply circuit for said primary and secondary circuits, whereby current is established across the gap when the same has been bridged by the secondary voltage and resistance means for preventing the supply current from maintaining an arc discharge across the interrupter contacts.

4. A discharge system comprising a primary circuit. containing a transformerprimary and a circuit interrupter, a secondary circuit containing a transformer secondary and a'gap, means for varying the length of ,saidgap at a predetermined rate, a common supply circuit connected to said primary and secondary circuits and an oscillating circuit comprising a condenser, said transformer primary and said interrupter, whereby when the gap is bridged by the secondary voltage, the current from the supply circuit is established across said gap, the resistance of the primary circuit being high; in comparison to that of the gap circuit, to prevent the establishment of the supply circuit current across the interrupter contacts.

' 5. A discharge system comprising a primary circuit containing a'transformer primary of low inductance and an electro-magnetic, circuit interrupter having an actuating coil located in the primary circuit, a secondary circuit containing a transformer secondary of low inductance and an adjustable gap, a common supply circuit connected to said primary and secondary circuits, an oscillating circuit comprising a condenser, said transformer primary andsaid interrupter, whereby when the gap is bridged by the secondary voltage, the current from the supply circuit is established across said gap, the resistance of the primary circuit being high in comparison to that of the'gap circuit, to prevent the establishment of the supply circuit current across the interrupter contacts and an inductance in said supply circuit having a value sufficient to prevent the high frequency currents of said primary and secondary from flowing into said supply circuit but insufficient toappreciably retard the establishment of the supply circuit current across said gap.

6. A welding system for butt we1ding, comprising a primary circuit containing a transformer primary and a circuit interrupter, a secondary circuit containing a transformer secondary and a gap produced between two members to be butt welded, a common supply circuit connected to said primary and secondary circuits and an oscillating circuit comprising a condenser, said transformer primary and said interruptenwhereby when the gap is bridged by the secondary voltage; the ourrent from the supply circuit is established across said gap, the resistance of the primary circuit be-. ing high in comparison to that of the gap circuit, to prevent the establishment of the supply circuit current across the interrupter contacts-and means forming a path of low impedance for the return to said transformer secondary of the high frequency current flowing across said gap and an inductance connecting said primary and secondary circuits, said inductance having a value sufiicient to prevent the passage therethrough of the high frequency currents of the secondary circuit, but insumcient to appreciably retard the establishment of the current from the supply circuit across said gap.

7. A discharge system, in combination; an induction coil, having primary and secondary windings; a secondary circuit including an air gap; a primary circuit; an interrupter in said primary circuit to induce a current in the secondary, bridging said gap; means including circuit connections for directing the primary current across said gap upon bridging by the secondary current, without passing through said primary and secondary circuits; and further means whereby the interrupter will be held open as longas the primary current flows across said gap.

8. A discharge system, in combination; an induction coil, having primary and secondary wind-.

preventing an are from forming at the interrupter contacts.

9. In a discharge system as described in claim 8, in which said primary circuit has two branches, one including said interrupter and the other including said gap, and in which'said last means consists of a resistance inserted in said interrupter branch.

10. A discharge system, in combination; an induction coil, having primary and secondary windings; a source 0! current supply; a secondary circuit or said induction coil, including a gap; a primary circuit including said interrupter and said source; means including circuit connections whereby the primary current will be broken in the primary circuit and directed across said gap without passing said primary and secondary circuits after said gap has been bridged by the secondary current, said primary circuit being held open so long as the primary current is maintained across said gap; said means automatically reestablishing the primary circuit to again break down the gap in case the'flow of the primary current across said gap ceases.

11. A discharge system, in combination; an induction coil having primary and secondary windings; a source of current supply; a secondary circuit including a gap; a primary circuit including an interrupter and said source; means including circuit connections whereby the current through said primary will be broken by said interrupter and directed across said gap, having been bridged by the secondary current, said primary circuit being held open so long as the current is maintained across said gap; said means automatically reestablishing the primary circuit to again break down said gap upon ceasing of the flow of the primary current across said gap; and means for preventing an are from forming at said interrupter.

12. A discharge system as described in claim 11, in which the primary circuit has two branches, one including said interrupter and the other including said gap; and a high resistance inserted in said interrupter branch.

13. An electric discharge system, in combination; a source of supply; a pair of discharge electrodes, forming a gap; an electromagnetic interrupter, having an actuating coil and a pair of cooperating contacts; said source, said coil and said gap being connected in series to form a main discharge circuit; an induction coil, having primary and secondary windings; a primary circuit in cluding said primary winding, connected across said gap in series with said contacts and an impedance; and a secondary circuit including the secondary of said induction coil, also connected across said gap.

14. A discharge system as described in claim 13 in which a condenser is connected parallel to the series combination formed by said primary winding and said contacts.

15. A discharge system as described in claim 13, in which a condenser is connected in parallel to the series combination formed by said primary and said contacts; and a further condenser in series with said secondary; the primary and secondary oscillatory circuits being tuned to the same frequency.

16. A discharge system, as described in claim 13; a choke coil in said discharge circuit in series with said gap; in which said secondary winding is connected directly across said gap and said primary circuit is connected across the series combination, comprised of said gap and said choke coil, respectively.

17. Ina system as described in claim 13, in which said impedance is a non-inductive resistance.

18. A discharge system as described in claim 13, in which said contacts are normally closed and held open upon and by the establishing of a main arcing current through said gap.

CHARLES E. VAWTER.-

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