US2440154A - Spark gap - Google Patents

Description

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Filed July 4, 1945 v INVENTOR fierfier/ L? fills B mronwsy Patented Apr. 20, 1948' OFFICE SPARK GAP Herbert E. Oles, Indianapolis, Ind., assignor to 1. P. B. Mallory & 00., Inc., Indianapolis, Ind., a Y

corporation of Delaware Application July 4, 1945, Serial No. 803,204

, i Claims. 1

capable or building up a high voltage between" the electrodes so as to produce a spark discharge the ends of which are inserted into the annular channel ll of the end plates. Preferably, end plates I! are constituted of a suitable iron-chromium alloy'which may be directly sealed to glass between the same. The spark discharge may be used to produce high frequency oscillations in a work circuit and for other purposes. Spark gaps of the described character are disclosed, for example, in' Patent #2,354,786 granted to Alexander 0. Wall on'August 1, 1944, and also in a copending application of Alexander 0. Wall and Herbert E. Oles, Serial Number 582,136, filed on March 10, 1945.

It is an object of the present invention to improve the characteristics of spark gaps or impulse gaps oi the described type.

It is another object of the invention to provide a method of producing spark gaps having extremely stable characteristics and particularly having a very stable break-down voltage.

Other and further objects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawing; in which Figure 1 is' a longitudinal sectional view of a spark gap embodying the invention during the process of its manufacture; I

. Figure 2 is a. circuit diagram of a typical impulse circuit employed in carrying the principles or the invention into practice; and

Figure 3 is a sectional view of the finished spark gap embodying the invention. 1

Referring now to Figure 1 of the drawing, ref: erence numeral l0 denotes a gap electrode of a generally circular shape constituted of a suitable refractory metal, such as for example, tungsten. This electrode is brazed or otherwise mounted on a cup-shaped electrode holder plate ll. vAn

plished by means of a spacer tube I! of glass or some other material of an insulating character,

thereby providing a stable and hermetically sealed construction. The inner space surrounding the electrodes and defined by end plates l2 and spacer tube II is initially in communication with the external atmosphere through openings or ports l8 provided in the electrode holder plates II and through openings ll in the center portion of the end plates l2. One of the openings ll may be sealed by means of a glass head I 8 while the corresponding. opening ll of the other end plate has'a glass tube l9 sealed thereto and provides a channel or duct through which the inner space of the gap may communicate with the external atmosphere. As spark gaps .of the described character and the method of making the same are fully disclosed in the said co-pending application Serial No. 582,136, no detailed description of the construction or the gap will be necessary.

I have discovered that the operating characteristics of a gap of the described character may be reatly improved by means of a special conditioning treatment after the structural completion of the gap and prior to applying the final seal thereto. This treatment comprises connecting the gap in a typical impulse circuit which periodically applies high voltages to the electrodes of the gap. The impulse generating circuit may comprise a suitablev source oi. electromotive'force, such as a conventional ignition magneto. The

wave formgenerated may; be such that it has approximately .a 1000cyclerate of rise and the output may be approximately 2000 volts peak nose or the plug. The application of these periodically acting impulses may be carried on for an extended period such as for twenty hours, or more. It has been found that if the .gap is filled with a suitable gas after this treatment and sealed, a spark gap or superior operating characteristics and of greatly increased stability is obtained. .In accordance with theprinclples or the present invention, this gas is a mixture-of oxygen and nitrogen, the preferred mixture comprising about 2%% of oxygen and about 97 of nitrogen.

The invention will now be more fully described in connection with Figure 2 in which a typical impulse circuit is diagrammatically shown. The

circuit comprises a magneto, generally denoted by reference numeral 20. The magneto includes aprimary winding 2| and a secondary windin 22, which are inductively coupled to each other. One end of. both windings is grounded and a condenser 23 is connected across primary winding 2|. The magneto also includes a pair of interrupter Y contacts 24 operated by means of a rotary cam 25.

Another condenser 26 of suitable capacity is connected'across secondary winding 22 of thewith a suitable gas, such as nitrogen, undera pressure of fifty pounds per square inch, in order to simulate the operating conditions within the cylinders of an internal combustion engine.

4 produced in accordance with the principles of the present invention provides important advantages. Thus, the spark gaps made by the method of the invention possess extremely stable p ysi al characteristics. For example, the voltage necessary to produce a dischargebetween the electrodes will vary only as little as five per cent or less. Moreover, spark gaps prepared according tothe invention will retain their desirable physical characteristics for a'very long time and as a result, have a very long useful life. a

The physical principles underlying the described presparking. treatment and responsible In carrying out the method of the invention,

the spark gap 21 to be treated is connected into the impulse circuit of Figure 2. In order to obtain the desired results, it is essential that the gaseous products of the presparking treatment he con tinuously removed from the interior of the spark gap. In the simplest case, this may be accomplished by maintaining the interior of the gap in communication with the atmosphere through ports l6 and i1 and glasst-ube [9 (Fig. 1). It is also possible, however, to pass a fiow of a filtered and cleaned gas. such as air. through the gap, said flow being introduced through tube l9 and up transformer. An oscillatory current of similar high frequency but of considerably higher voltage will be,built up across secondary winding 29 and will produce high frequency sparks between center electrode 30 and electrodes 33 of spark plug 3!.

This presparking treatment is preferably continued for an extended period of time such as for twenty to forty hours. In general, a presparking treatment for approximately twenty hours at about twenty-two sparks per second has been found to provide satisfactory results.

After the presparking treatment has been completed, the spark gap may be evacuated, filled with a suitable gaseous charge, and is hermetically sealed. In accordance with the invention, this charge comprises a mixture of oxygen and nitrogen, in the proportion of about 2%% oxygen and 97 /295 nitrogen. This charge may be under normal atmospheric pressure or under some other suitable pressure.

The finished gap isillustrated in Figure 3 and is in every respect'identlcal with that shown in Figure 1, except that glass tube l9 has been sealed on close to the lower end plate, constituting a glass bead 34 similar to glass bead l8 sealing the upper end plate.

Experience has demonstrated that a spark gap withdrawn or discharged through port ll before 1 for the greatly improved operating characteristics of the gaps treated in accordance with the invention are not fully understood. 'It is believed that during the presparking treatment, minute but critically important changes are caused in the electrode surfaces, while the gaseous and solid by-products of the treatment are removed for example by permitting them toescape into the atmosphere. Therefore, any possible initial changes in the physical characteristics of the electrodes and of the gap will already occupduring the presparking period which is continued until such characteristics are permanently stabilized. While this explanation appears to be well supported by experimental evidence, the invention is, of course, independent from the'merits of any theoretical consideration.

Although the present invention has been disclosed in connection with a preferred embodiment thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the invention. I consider all of these variations and modifications to be within the true spirit and scope of the present invention, as disclosed in the foregoing description, and defined by the appended claims.

The present application is related to my copending application Serial No. 603,203, filed concurrently herewith, wherein my method of presparking spark gaps and the products of such method are broadly claimed.

What is claimed is: e

1. The method of making spark gap's which .comprises providing a pair of spaced electrodes in a container, producing periodic electrical sparks between said electrodes while continuously removing the gaseous products of such discharges, replacing the atmosphere within said container with a gaseous charge consisting of a mixture of nitrogen with a small percentage of oxygen and then hermetically sealing said container.

2. The method of making spark gaps which comprises providing a pair of spaced electrodes in a container, producing periodic electrical sparks between said electrodes while permitting the gaseous products of such discharges to escape into. the atmosphere, evacuatingsaid container, introducing a mixture of about 2Vz% oxygen and about 97/z% nitrogen into said evacuated container, and then hermetically sealing said-container.

3. The method oi making spark gaps which comprises providing a pair of spaced electrodes in a container, producing periodic electrical sparks between said electrodes while passing a flow of a cleaninggas through said container, filling said container with a mixture of about 2 oxygen and about 97 /2% nitrogen, and subsequently hermetically sealing said container.

4. The method of making impulse gaps of stable characteristics which comprises providing a pair of spaced plane electrodes constituted oi refractory metal within a gas-tight container, maintaining said container in communication with the external atmosphere, presparking said electrodes for a period or several hours, fllling said container with a mixture of about 2 /2% oxygen and about 97 /2% nitrogen, and then hermetically sealing said container.

5. The method of making impulse gaps of stable characteristics which comprises providing a pair of plane parallel-spaced tungsten electrodes within a vessel adapted to be hermetically sealed. initially maintaining the interior of said vessel in communication with the external atmosphere, connecting said electrodes to an impulse circuit to produce aplurality of electric sparks per second between said electrodes for a period of several' hours, filling said vessel with a mixture of about 2/% oxygen and about 97 /z% nitrogen, and hermetically sealing said vessel after filling thereby to obtain an impulse gap of stable operating characteristics.

6. The methodof making impulse gaps of stable characteristics which comprises providing a pair of parallel-spaced circular tungsten electrodes within a vessel adapted to be hermetically 6 and the external atm phere. presparking said electrodes for a predetermined period while maintaining such communication, filling said vesse1 with a mixture or about 2%% oxygen and about 97 /2% nitrogen, and then hermetically sealing said vessel.

8. An impulse gap of stable characteristics comprising a hermetically sealed vessel. 9. .pair of generally plane presparked electrodes constituted of refractory metal spacedly mounted in said vessel, and a mixture of about 2%% oxygen and about 928596 nitrogen in said vessel.

9. An impulse gap of stable characteristics comprising a hermetically sealed vessel, a pair of generally plane electrodes spacedly mounted in said vessel, and a gaseous charge sealed within said vessel, said charge substantially consisting 01' a mixture of about 2%% oxygen and about 97 nitrogen.

10. An impulse gap or stable characteristics comprising a hermetically sealed vessel, a. gaseous atmosphere in said vessel consisting of about 255% oxygen and about 97%% nitrogen. and a pair of plane electrodes constituted of refractory metal mounted in said vessel in parallel-spaced a position, said electrodes having surfaces of such sealed, maintaining the gaseous atmosphere within said vessel in communication with the external atmosphere, connecting said electrodes to an electrical impulse circuit to produce electric 3 sparks in the order of about twenty sparks per second for a period in the order of about forty hours, filling said vessel with a mixture or about 2%% oxygen and about 97% nitrogen, and hermetically sealing said vessel after filling thereby 35 to obtain an impulse gap of stable operating characteristics.

7. The method of making impulse gaps of the type including a pair of spaced electrodes within a sealed vessel which comprises establishing communication between the interior of said vessel physical characteristics as is obtained by presparking them for an extended period.

HERBERT E. OLES.

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

UNITED STATES PATENTS Number Name Date 1,879,131 Dabke Sept. 27, 1932 1,933,329 Hull Oct. 31, 1933 1,965,584 Foulke July 10, 1934- 2,199,866 Alterthum May ,7, 1940 2,288,861 Watrous July '7, 1942

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