US2422659A - Spark gap discharge device - Google Patents

Description

June 1947- c. DEPEW ET AL SPARK GAP DISCHARGE DEVICE 2 Sheets-Sheet 1 Filed Aug. 21, 1945 V MAX.

V OPERATING 1 MIN. I

c. DEPEW INVEN7ORS: w A. DEPP A. N. LUCE 9 15 TIME IN HOURS ATTORNEY June 1947- c. DEPEW ET AL SPARK GAP DISCHARGE DEVICE Filed Aug. 21, 1943 2 Sheets-Sheet 2 "c. DEPEW lNVENTORSi W A. DEPP A 7' TORNEV Patented June 24, 1947 STATES TENT OFFICE SPARK GAP DISCGE DEVICE Application August 21, 1943, Serial No. 499,502

13 Claims.

This invention relates to spark gap discharge devices and more particularly to such devices operatin in a stable gaseous atmosphere at high pressure for controlling an ionizalble discharge within definite limits of breakdown voltage.

The attainment of constant controlling characteristics in a spark gap discharge device and the prolongation of its operating life over a long period, particularly with respect to constancy of its definite breakdown limits especially useful in triggering the device in pulse signaling systems of high voltage and high periodicity, entail many variable factors which render the spark discharge unstable. Some of these factors affect the starting discharge, the operating discharge, the type of discharge, the time lag, electrode sputtering, erosion, deionization, maintenance of uniform spacing between the electrodes and the instantaneous sharp cut-ofi of the spark discharge to eliminate destructive glow persistence in the discharge.

In order to achieve stable operation over a range substantially between 1 kilovolt and kilovolts, it is essential that the gap between the electrodes should break down so that a low voltage drop exists between the electrodes to prevent a transient high pressure glow occurring to prolong the discharge which results in excessive sputtering of the electrodes and particularly the cathode whereby the uniformity of gap spacing between the electrodes is soon altered thereby resulting in irregular operation and short operating life. Furthermore, after initial breakdown of the spark gap at relatively large current is conducted through the device at a relatively high repetitious rate, for instance, of the order of 1,000 pulses per second and such characteristics can be maintained over a relatively long operating life.

An object of the invention is to insure stable operation of the discharge gap in a unidirectional path which is substantially confined by one of the electrodes.

Another object of the invention is to facilitate the breakdown of the gap within a wide range of voltages over which triggered operation is obtained.

A further object of the invention is to initiate conduction between solid electrodes in a gasfilled vessel at a low triggering voltage. 4;

Another object of the invention is to increase the efficiency of the discharge gap between the electrodes by the provision of initiative components in the enclosure within the confines of the gap.

A further object of the invention is to increase 2 the stability of the discharge gap in a controlled atmosphere by the incorporation of multiple corona points in the gap.

Still another object of the invention is to facilitate the operation of the device over a long period without material alteration of the space relation of the electrodes in the gap due to the sputtering of cathode material.

In accordance with this invention the spark gap discharge device comprises a gas-filled receptacle of the cartridge type having terminals at opposite ends which are joined to oppositely disposed central conductors sealed in the receptacle.

A cylindrical anode rod is attached to one of the conductors and extends axially within the receptacle and a cup-shaped cathode is carried by the other conductor and is uniformly spaced from the sides and end of the anode rod which it surrounds.

The cathode is rigidly afiixed to the conductor by an intermediate sleeve member mechanically and electrically joined to the cathode and secured to the conductor. In another form of the device the anode may be afiixed to its respective con.- ductor in a similar manner. The receptacle is provided with a gaseous filling, such as hydrogen, at a pressure extending over a range from onehalf to several atmospheres, depending on the range of voltages applicable to the device, to stabilize the spark discharge and also facilitate the constancy of the operation of the device with high efficiency over a long life. The enclosed cathode structure materially enhances the uniformity of the spark discharge by decreasing the sputtering effect produced in the gap. The cathode is also provided with a shielding skirt portion which surrounds the anode termination to prevent the discharge being lengthened to the exterior surface of the cathode, and to materially decrease the deposition of sputtered material from the cathode onto the wall of the receptacle.

Another feature of this construction is the inclusion of multiple corona points within the confines of the cathode to insure constant firing of the discharge gap at the instant of maximum potential whereby ultra-violet radiation from the corona reduces the time lag in the initiation of the discharge breakdown between the cathode and anode. This is accomplished by the provision of a star-shaped member enclosed in the cathode and closely associated with the discarge path so that the array of points facilitates the primary sparking of the gap. This arrangement materially increases the accurate breakdown of the discharge gap with minimum time lag.

3 4 A further feature of the invention relates to the termination of the spark discharge immediately after breakdown of the gap to prevent the "establishment of a transient high pressure glow discharge having a high cathode fall of potential. The glow discharge is eliminated by the addition of an inert gas, such as argon, together with the hydrogen filling in the proportions of approximately 25 per cent argon and '75 percent hydrogen.

A further feature of the invention relates to the coupling of the terminal contacts of the cartridge vessel to the conductors in the device to compensate for temperature changes due to the high potentials incident to the operation of the discharge gap. This arrangement utilizes a flexible coupling between the conductors and the terminals of the device to neutralize excessive temperature variations between the conductors and the caps to overcome leakage or fracture of the seals which might endanger the use of the device by leakage. of oxygen into the gaseous filling causing damageor explosion of the device.

These and other features and advantages will be more clearly set forth in the following detailed description which, together with the accompanying drawings, embodies a complete disclosure of this invention. a

Fig. 1 illustrates in an elevational cross-sectional view, the embodiment of thisinvention of a high breakdown voltage spark gap discharge device;

Fig. 2 is, the same view of the device of Fig. l with the coaxial electrodes shown in full View and the device turned 90 degrees. to illustrate the coupling of the cathode to its conductor;

Fig, 3 is a graphic plot of the maximum and minimum voltage limits and the operating characterist'ic of the device intermediate these limits to insure safe margins for the control characteristics of the device;

Fig. 4 is a plan view of Fig. 44.; v

.Fig. 5 isan enlarged perspective .view of the multiple corona point element enclosed within the cathode as shown in Fig. 1;

Fig. 6 shows an enlarged fragmentary view in cross-section of the coupling connection of the cathode and its supporting sleeve;

Fig. 7 is a view in cross-section of a modified form of. the invention in which both electrodes are. of like metal and a single corona point is located within the cathode; and

Fig. 8 illustrates another modification in crosssection showing details of assembly and a dielectric shield embracing the anode conductor adjacent the seal.

Referring tothe drawing, and particularly to Figs. 1 and a high voltage spark gap discharge device of this invention capable of conducting high currents, of the order of 200 amperes, embodies a cylindrical cartridge type vessel or receptacle I0 having tungsten conductors I I and I2 sealed in opposite ends and extending within the vessel along the axis thereof. A solid nickel rod I3 extends along the axis of the device and isprovided with a rounded or dome end while the opposite 'end is tapered and welded to conductor I2 extending irom one end of the vessel. The nickel rod which functions as the anode of the device in a particular embodiment is formed of a rod of 16 inch diameter and is substantially wholly enclosed by a cylindrical,cup-shaped aluminum cathode I4 whichiscoaxially mounted about the anode I;-3,; the cathode having a thick wall portion adjacent the free 'end of the anode 1 taken on the line 4 and a depending skirt portion I5 of one-half the thickness of the main wall portion surrounding the terminal end of the anode with the space relation between the internal wall of the cathode and the lateral surface of the anode being approximately mils or .150 inch. The main discharge occurs across the gap between the heavy wall portion of the cathode and the end of the anode which it surrounds, while the skirt portion I5 of the cathode materially reduces the escape of any sputtered material to the wall of the vessel. The cathode is preferably formed of aluminum to reduce the sputtering rate in the high voltage spark discharge gap and the improved construction materially limits the spark discharge to theactive surfaces of the electrodes where it is wholly confined.

In order to initiate ionization between the electrodes to effect breakdown of the gap therebetween, a material I6 is deposited within the oathode enclosure to effect the presence of free ions in the discharge gap. This material may be radium bromide or chloride which is painted on the cathode surface in the. form of small spots to introduce the desired amount of ion producing substance therein which is approximately 2 micrograms. In addition, the. breakdown discharge in the gap is initiated with a minimum of time lag by a mult'ipoint element, as shown in Fig. 5, which is formed of a steel plate. I! of star shape having the points I8 bent at right angles to the plane. of the base of the plate to provide a multiplicity of corona discharge points for the initiation of the breakdown of the discharge to the rounded end of the anode I3, the multicorona point element being positioned coaxially on the end wall of the cathode I4 and wholly enclosed in the discharge gap within the immediate firing areaof the discharge, the points being equally distributed about the end of the anode approximately at a distance of 1% of an inch. The corona point element is rigidly affixed to the cathode by an eyelet I9 and the assembled construction is secured to the conductor II by a steel coupling sleeve 20, by welding the spun end of the sleeve to the eyelet and the slotted shank 2| to the conductor I 'I. The vessel is filled with a gaseous mixture of hydrogen 'Z5Yper cent and argon 25 per cent at a pressure from 45 .to '67 centimeters of mercury or approximately two-thirds atmospheric pressure, thehydrogen being purified by passing it over palladiumized asbestos to remove oxygen. A terminalcap 22 is cemented to one end of the vessel through which conductor 12 extends for the anode anda larger diameter terminal cap 23 is cemented to the other end of the vessel through which extends the cathode conductor I I to polarize the device and insure the correct insertion of the device in a mounting. These terminal capsare attached to the respective conductors by flexible straps 24 and 25, respectively, to compensate for temperature changes in the expansion and contraction of theconductors under. the high temperature andhigh current operation of the device to protect the hermetic seals of the conductors in the device.

The correlation of the various components entering into the construction of the improved spark gap trigger device of this invention results in securingthemost eflicient operation and a relatively long operating life despite the high currents encountered inthe intensive character of the discharge. Furthermore, the extent of the controlling range is substantially constant throughout the continued operation of the device.. This isattributable to the distributionof the'discharge in a rotating direction over the inner surface of the cathode and the symmetry of the electrodes, their physical character and terial is'more uniform over the discharge surface of the cathode so that concentrated deposit on the-anode is avoided.

The conditions of operation of the device may be realized from a perusal of the time vs. voltage diagram shown in Fig. 3, in which hours of operation are plotted as ordinates and the voltage range as abscissae. The working range for a typical device is shown in the form of solid dots varying but slightly with time where at slightly below 8,000 volts the maximum voltage or Vmax is represented as the upper limiting Voltage of the device over which the spark discharge changes 'to a continuous arc discharge. The lower limit of the device is in the 3,000 to 4,000 volt range below which the device fails to spark without interruption. Selecting a medial point between these limits represents a safe operating potential or V operating characteristic which insures an adequate margin above and below the operatin voltage so that the device may be operated within the range represented by the upper and lower dots at a definite time interval.

The static spark gap device, as shown in Fig 1, is usually operated in pairs or three in series with unlike electrodes connected together for switching pulsing circuits of high periodicity, three or more units being employed for exceedingly high voltages while two units are commonly employed for a voltage range from 3 to 8 kilovolts, the controlling voltage being applied to the common point of the pair of units to trigger the gaps substantially simultaneously.

The presence of the radium bromide E6 in the cathode enclosure insures adequate free ions in the firing gap to initiate the discharge when the breakdown potential is applied and the multicorona points l8 equally distributed from the end of the anode l3 facilitate the instantaneous ionization of the gap with a minimum time lag to fire the gap at a minimum sparking voltage.

The high periodicity of the spark discharge in pulsing circuits and the high potentials employed in operation necessarily increase sputtering of material from the cathode but due to the symmetry of the electrodes the material is deposited on the anode surface and, consequently, the gap space relation between these electrodes remains essentially constant thereby insuring uniformity in the characteristics of the discharge. Furthermore, the aluminum cathode [4 decreases the sputtering rate so that a relatively long operating life is assured. The shielding portion or skirt I5 of the cathode also enhances the continued operation of the device, since the length of the cathode is sufiiciently greater than the spark length so that the discharge does not escap from the concentrated path adjacent the dome end of the anode. Similarly, the skirt portion protects the wall of the vessel I from sputtered material emanating from the cathode thereby increasing the insulation resistance between the terminal portions of the respective electrodes. The preservation of the high dielectric properties of the vessel is a decided advantage in the high voltage operation of the device,

The i since the breakdown voltage can be divided equally to the units in series to eifect simultaneous triggerin of the gaps and avoid preferential arcing in one device which would occur if leakage paths were formed between the terminals of the electrodes.

A modification of the invention is disclosed in Fig. 7 in which the electrodes are formed of similar materials and the starting discharge is considerably reduced by the incorporation of a single corona, point wholly enclosed in the firing path of the discharge. In this construction the cathode conductor H is provided with a sharpened point 26 which extends within the cathode I4 and is directly opposite the dome end of the anode enclosed within the cathode. The anode l3 in the device shown in Fig. '7 is slightly different in construction from the anode described in Fig. 1, since this anode is formed of aluminum and is, therefore, of the same material as the cathode [4, the aluminum rod being provided with a shank portion 21 exterior to the cathode and being aligned with the conductor ['2 by a coupling sleeve 28 which is secured to the shank by a pin 29 and welded to the conductor 12 along the slot 30 therein. In this construction both electrodes are mechanically and electrically connected to the conductors by coupling sleeves to securely fasten the aluminum electrodes to the tungsten leading-in conductors of the device. Another change in the construction of the device, as shown in Fig. 7, is the connection of the conductors in the vessel to the terminal caps on the ends thereof. Each cap 3! is cemented to a reduced portion of the enclosing vessel adjacent the leading-in conductor and is provided with a central depressed portion through which the conductors l l or l2 extend. A flanged sleeve 32 is welded to the conductor exterior to the shell or terminal and the flange portion is embedded in a fusible metal mass 33, such as solder, to provide a flexible connection in the cap to compensate for expansion and contraction in the seal of the conductor entering the vessel.

A further modification of the invention is shown in Fig. 8 in which an anode rod 34 of nickel or aluminum is counterbored to receive the end of the conductor [2 extending into the vessel, the anode being secured to the conductor by a transverse pin 35. The cathode 36, preferably formed of aluminum, has an elongated wall completely surrounding the anode 34 and is provided with a cylindrical bored extension 37 through which the sharpened corona point conductor ll extends, the cathode being rigidly secured to the conductor by a transverse pin 38. In this construction a dielectric flanged cup shield 39, formed preferably of glass, is sealed to the conductor l2 and also to the vessel [0 with the flanged portion 40 projecting toward the open end of the cathode so that any sputtered material escaping from the'discharge path between the electrodes will be deposited on the surface of the shield and, therefore, will not endanger the insulation path along the inner wall of the vessel between the oppositely disposed conductors H and I2 of the electrodes.

While various modifications and structural assemblies of the devices of this invention have been disclosed, it is, of course, understood that other mechanical changes can be incorporated in the structural features of the device of this invention without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

anaageacz 77. 1: ionic pulsing relayrhaving; high breaks dom -periodicity characteristics; comprising. a

vessel containing. a; gaseous fillingarsubstantiallyi at-- pressures fromone-half; to; several; atmospheresindiVidual conductors sealed in eachiend;

vessel containing a gaseous filling substantially at atmospheric pressure, individual conductors sealed in each end ofsaid vessel and extending along the axis thereof, a cylindrical anode rod of solid nickel carried byione of said conductors, an elongated cup-shaped aluminumcathode", coaxiallyisurrouuding said anodeacross a short gap and supportedby the other conductor, and multiple corona points equally disposed opposite theend of said anode and supported. by saidcathode.

3. An ionic trigger device comprising a cartridge type vessel containing a gaseous filling substantially at atmospheric pressure, individual conductors sealed-in each endof said vessel and extending along the axis thereof, a rod-shaped anodecarried by one of said conductors, an elongated cup-shaped cathode --concentrically surrounding said anode across a short gap and supported by the other. conductor, a corona point element supported in the base-oi said cathode and disposed opposite-the end ofsaid anode, terminal caps on opposite ends-of said vessel surrounding said conductors, and flexible connec tions between said conductors and said terminal caps.

4. An ionic trigger device comprising a cartridge type vessel containing a gaseous filling sub stantially at atmospheric pressure, individual conductors sealed in each end of said vessel and extending along the axis thereof, a rod-shaped anode carried by one of said-conductors, an elongated cup-shaped" cathode concentrically surrounding said anode across a short gap and supported bythe other conductor, multiple corona.

points equally disposed opposite the end of said anode and supported in the base ofsaid cathode,

a cup-shaped terminal on one end of said vessel for said anode,- a larger diameter cup-shaped terminal on the other end of said'vessel for said' cathode, and resilientmetallic connectors extending between said terminals and the conductors for said cathode and anode.

5. Anionic trigger device comprising a cartridge type vessel containing a gaseous filling substantially at atmospheric pressure, individual conductors sealed in each end of said vessel and extending along the axis thereof, a-rod-shaped anode carried by one of said-conductors,- an elongated tubular cathode concentrically surrounding said anode across a short gap and supported by the other conductor, and a star-shaped metallic member having the points bent at an-angle securedto the innermost end of said cathode, said points being directed towards: said anode."

'6. An-Jionic trigger. device comprising a car tridge; type. vessel containing ia gaseous filling of zhydrogen and argon substantially at atmos= pheric. pressure, individual conductors sealed in eachiend of :said vessel and extending along the:

axis :thereof, a rod-shaped 'anode 'carried by one of'rsaid conductors, an elongated tubular aluminum cathode concentrically surrounding said anode. across-a short gap; andsup'ported" by theother conductor, and a multipoint metallic member secured to the wall of said cathode opposite the active end of said anode th'ewpoints:thereof extending parallel-to theside wall of said cathodeand spaced in equal distribution fromthe activenndofsaid anode.

7. Anionic trigger device comprising/a cartridge type Vessel containing a gaseousfilling of hydrogen and argon substantially at atmospheric pressure, individual conductors sealed in' each end: of said :vessel and extending along the axis thereof, a. rod-shaped anode carried by one of saidiconductors' and extending axially alongsaid 1 vessel, an elongated cylindricalfialuminum cathode concentrically surroiinding said anode across a short gap andsupported by the other conduc tor, a corona point. element wholly enclosed in said cathode and directed toward the end of said anode, and a coupling sleeve attached to said cathode, element and'said conductor.

83An. ionic.trigger device comprising acartridge type vessel containing agaseous filling of hydrogen and argonsubstantially'at atmospheric pressure, individual conductors sealed in eachend of said .vessel and extendinglalong the axis thereof; a rod-shapedanode carried by one of sai'dcon ductorsand extending along the axis of said-vessel, an elongated tubular aluminum cathode concentrically surrounding said anode across a short gap. and supported by the other conductor, a

corona point elementuwholly enclosed 'in' said cathode and directed toward the end oflsaid anode, an eyelet clamping said member to'the inner surface of said cathode; and a slotted sleeve Welded. to said eyelet and said'conductor;

9; An ionic trigger device comprising a cartridge :type vessel containing a gaseous mixture substantially at atmospheric pressure, a'pair. of lead-in wires sealed in opposite ends of said vessel,"a centraliele'ctrode, and a hollow concentric electrodevenclosingsaid central electrode, one of said wires having a sharp point extending axially, of andwithin'said hollow electrode and shielded thereby, and metallic sleeve members rigidly coupled to said ilead-in' wires and. said electrodes i respectively.

10. "A high voltage spark gap. trigger device it comprising a cartridge type vessel-containing Jan ionizing mixture ofhydrogen and argon iat a pres-' surefrom-A5 .to 6'7 centimeters of'mercury, cenJ- .tral iconductors extending into opposite ends of: said vesseLa cylindrical cup-shaped cathode supported co.--axial1y in said vessel, a cylindrical rod-' shaped anode extending axially within said oath ode'and connected :to the other conductor, means to initiateionization in said. mixture,.m'eans=position'edtini the base of :said cup-shaped cathode for. .facilitating. a coronadischar ge in J said gap betweenxsaid :cathode. and .anode; and f a cupshaped'nshield member on .said conductor sup-' cathode;

porting. said anode and extending toward said."

11.1Ahigh voltage spark 'gapitriggeri device 1 comprising a cartridgetype vessel containing; an ionizing: mixture" of hydrogen and argonat a pressure of-45 centimcters of mercury; central conductors extending into opposite ends of said vessel, a cylindrical cup-shaped ,cathode sup ported. coaxially in said vessel, a cylindrical rodshaped anode extending axially Within said cathode and connected to the other conductor, means to initiate ionization in said mixture, means positioned in the base of said cup-shaped cathode for facilitating a corona discharge in the gapbetween said cathode and anode, and terminal caps attached to opposite ends of said vessel, said conductors extending therethrough and being soldered to said cap,

12. A high voltage spark gap trigger device comprising a cartridge type vessel containing an ionizing mixture of hydrogen and argon at a pressure of 45 centimeters of mercury, central conductors extending into opposite ends of said vessel, a cylindrical cup-shaped cathode supported coaxially in said vessel and attached to one of said conductors, a cylindrical rod-shaped anode extending axially within said cathode and connected to the other conductor, means to initiate ionization in said gaseous mixture, and said conductor supporting said cathode having a sharp point extending Within said cathode body and spaced directly opposite said anode.

13. A high voltage spark gap trigger device comprising a cartridge type enclosing vessel, an ionizable gaseous mixture therein composed of 75 per cent hydrogen and 25 per cent argon at a pressure of 45 centimeters of mercury, oppositely disposed tungsten conductors sealed in the ends of said vessel and extending along the axis thereof, an aluminum shell type cathode having different wall thicknesses along its length, said cathode having an apertured end portion surrounding one of said conductors, a star-shaped plate having upturned points abutting against said apertured end portion of said cathode, a solid nickel anode rod extending within said cathode shell an supported coaxially therein by said other conductor, the diameter of said anode rod and the space relation of said upturned points from the end of said anode being substantially of the order of f g of an inch and the radial spacing of said cathode Wall from the lateral surface of said anode being approximately of an inch, a metallic eyelet securing said plate to said cathode, and a tubular steel coupling intermediate said cathode and said conductor rigidly affixed to said eyelet and said conductor.

CHARLES DEPEW.

WALLACE A. DEPP.

ALFRED N. LUCE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,531,301 Metzger Mar, 31, 1925 1,656,957 Schroter Jan. 24, 1928 1,760,524 Rentschler -L May 27, 1930 1,990,177 Friedrichsen Feb. 5, 1935 2,071,748 Hund Feb. 23, 1937 2,354,786 Wall Aug. 1, 1944

Images