US2310092A - Electric discharge apparatus - Google Patents

Description

Feb. 2, 1943. D. D KNOWLES E'TAL 2,310,092

ELECTRIC DI SCHARGE APPARATUS Original Filed May 17, 1955 2 Sheets-Sheet 1 Master OsciZ/aior WITNESSES: INVENTORS A/ Dewey D. Know/9s zZ/z. and Ce c zlE Hal/er,

Feb, 2,; 1943. D. D KNOWLES Em, 2,310,092

ELECTRIC DIS CHARGE APPARATUS Original Filed May 17, 1935 2 Sheets-Sheet 2 VAB/AB LE SPEFD w 2 14 BL E FREQ UENC r WITNESSES: INVENTORS Dewey fl. Knew/65. and gcziil f/a/Zer.

Fatented Feb. 2, Q43

gunner v ELECTRIC DISCHARGE APPARATUS Dewey D. Knowles, Forest Hills, Pa., and Cecil E.

Haller, Bloomfield, N. J., assignors to Westinghouse Electric 8; Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Original application May 17, 1935, Serial No.

Divided and this application January 16, 1937, Serial No. 120,940

24 Claims.

Our invention relates to electric discharge apparatus and it has particular relation to the control of electric discharge devices of the type having a discharge initiating electrode, but not a discharge maintaining electrode such as a keep-alive.

This application is a division of our application Serial No. 22,012, filed May 17, 1935, and now U. S. Patent No. 2,085,100 granted June 29, 1937.

It is an object of our invention to provide a circuit for controlling the initiation and extinction of the discharge in a discharge device of the mercury pool type that is equipped with a discharge initiating electrode.

Another object of our invention is to provide apparatus for periodically energizing a discharge device of the mercury pool type that is equipped with a, discharge initiating electrode. I

A further object of our invention is to provide apparatus for energizing, and deenergizing, with variable periodicity, a discharge device of the type that is normally completely deenergized.

More specifically stated, it is an object of our invention to provide apparatus for energizing and deenergizing, with precisely determinable periodicity, a discharge device of the type that is equipped with a discharge starting electrode, but not with a discharge maintaining electrode.

In the following discussion and in the claims, we shall refer to a discharge device having a plurality of principal electrodes and a plurality or pair of starting electrodes. Such an expression is drawn with the thought in mind that it shall denominate a discharge device having at least four electrodes, 1. e., separate pairs of principal and starting electrodes.

In the preferred structure of the discharge device utilized in the practice of our invention, however, only three electrodes are utilized; an anode, a mercury pool cathode and a starting electrode, preferably composed of boron carbide the solid starting electrode may be displaced a short distance from the pool and in initiating the discharge a spark may be ignited between the starting electrode and the pool. Moreover, the starting electrode may be a band surrounding the envelope of the discharge device in the region of the pool. It is to be noted, however, that while discharges oi. the latter types may be utilized, they offer difliculties when used for stroboscopic purposes. To ignite such discharge devices considerable and persistent starting potential is required and as far as we are aware, the operation of such discharge devices is uncertain. However, it should be kept in mind that while the discharge devices of the type incorporating the silicon or boron carbide starting electrode are preferable for stroboscopic work. where the discharge devices of the last-mentioned types have utility and where the teaching of our invention is otherwise followed such use of the discharge devices are equivalents which fall within the scope of our invention.

In accordance with our invention, a source of electrical energy is connected across the principal electrodes of the discharge device and a capacitor is connected in parallel with the principal electrodes. In the circuit of the starting electrodes of the discharge device a valve is connected. The supply of starting current through the valve and the rate of charge and discharge of the capacitor are so timed that the discharge device is energized and deenergized with the desired periodicity. The periodicity may be varied by varying the timing of the supply of starting current or by varying the rate of charge or discharge of the capacitor.

The novel features that we consider characteristic of our invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic view showing an embodiment of our invention;

Fig. 2 is a diagrammatic view showing a modification of our invention;

Fig. 3 is a graph illustrating the operation of the apparatus shown in Fig. 2;

Fig. 4 is a diagrammatic view showing a further modification of our invention;

Fig. 5 is a diagrammatic view showing a still further modification of our invention; and

Fig. 6 is a graph illustrating the operation of the apparatus shown in Fig. 5.

Our invention is illustrated herein as utilized in a stroboscope. For stroboscopic purposes, a luminous discharge which can be ignited and extinguished with a precise periodicity is a desideratum. However, as will be manifest from the following description, our invention may also be utilized for other purposes.

The apparatus shown in Fig. 1 comprises a discharge device I having an anode 3, a mercury pool cathode 5, and a starting electrode I composed of a high resistive material such as boron carbide or silicon carbide, a portion of which is immersed in the mercury 5. When the discharge device I is energized, as shall be explained hereinafter, the radiations emitted by the luminous spot formed on the mercury pool surface are projected on the body 9 under observation which is illustrated as the spoke of a rotating wheel II. The discharge device I is energized and deenergized at a periodicity corresponding to the periodicity of the wheel II and when the spoke 9 is observed in the illumination emitted by spot, it appears to be at rest. When We refer hereinafter to an electrode or a material of the igniter type we mean thereby an electrode such as 1 or the material of which it is formed. The material in question may be not only of silicon carbide or boron carbide but any other substance which when contacting an electrode and operated by current has the property of facilitating the initiation of an arc between said electrode and another electrode.

A capacitor I3 is connected to the anode 3 of the discharge device I through an inductor I and directly to the cathode 5 of the discharge device. The capacitor I3 is charged through a resistor I! from a source I3 which is preferably of the direct current type. The starting electrode 1 is connected to the capacitor I3 through an auxiliary discharge device 2! and the inductor I5. The auxiliary discharge device 2I is preferably of the type having an abrupt characteristic. It is provided with an anode 23, a hot cathode 25' and a control electrode 21 which are immersed in a gaseous medium. The anode 23 is connected to the inductor I5 while the cathode 25 is connected to the starting electrode I through a current limiting resistor 29. The control electrode 21 is connected to the cathode 25 through a variable biasing battery 3i.

In operation, the auxiliary discharge device 2i is normally deenergized. The capacitor I3 is charged through the resistor I1 in series therewith. When it attains a difference of potential predetermined by the magnitude of the bias in the control circuit of the auxiliary discharge device the latter is energized and a pulse of current is transmitted between the starting electrode 1 and the mercury pool 5. A discharge is, therefore, initiated between the principal electrodes 3 and 5 of the main discharge device I which persists for an interval of time predetermined by the relative magnitudes of the inductor I5 and the capacitor I3. The capacitor I3 is discharged when the main discharge device I is energized; and when the main discharge device is extinguished,

the capacitor is recharged and the above-de-rc scribed process is repeated. Since the electrode 1 and the mercury 5 both cooperate to produce an are, they may be designated together as a plurality of starting electrodes.

The excitation of the main discharge device I is periodic. The periodicity of the excitation may be varied either by varying the resistor I? in series with the capacitor I3, and thus varying the rate of charging of the capacitor, or by varying the biasing battery in the control circuit of the auxiliary discharge device, and thus varying the magnitude of the charge which is to be applied to the capacitor to produce excitation of the auxiliary discharge device. In the practice of our invention, either of these elements is so varied that the frequency of discharge of the main discharge device corresponds to the frequency of movement of the body 9 under observation. This correspondence is attained by subjecting the body 9 to the illumination from the discharge device and by slowly varying the resistor or the control battery until the body appears to be at rest.

In the apparatus shown in Fig. 2, the proper periodicity of illumination is attained by utilizing the output of a master oscillator 33, the frequency of which may be varied. Here again, a capacitor I3 is connected between the mercury pool 5 and the anode 3 of the main discharge device I. The capacitor I3 is charged from a source 34 through an auxiliary discharge device 35 of the type having an anode 31, acathode 39 and a control electrode 4|. If the source 34 utilizedfor charging is of the alternating current type, the auxiliary discharge device 35 should preferably be of the asymmetric type and should be so connected to the capacitor I 3 that the capacitor plate 43 which is connected to the anode 3 of the main discharge device I is charged positive.

The excitation of the auxiliary discharge device 35 is controlled from the master oscillator 33. A potential provided by the master oscil lator 33 is impressed between the control electrode 4| and the cathode 39 through a secondary section 45 of a suitable transformer 41 and the discharge device 35 is energized at a frequency corresponding to that of the master oscillator.

The master oscillator 33 also provides current impulses for energizing the main discharge device. F'or this purpose, another secondary section 49 of the transformer 41 is connected between the starting electrode and the mercury pool 5 of the main discharge device I through a suitable rectifier 5|. Half-wave impulses produced by the oscillator 33 are thus transmitted through the starting electrodes 1 of the main discharge device I and periodically initiate the discharge in the main discharge device, the anode-cathode potential being supplied by the capacitor I 3.

To provide for precise operation of the main discharge device I, the secondaries 45 and 49 of the oscillator transformer 41 are so wound that the initiating discharge is only transmitted through the starting electrodes of the main discharge device after the capacitor I3 has been charged and when the auxiliary discharge device 35 blocks the charging current. Preferably, the potential supplied to the control circuit of the auxiliary discharge device 35 is in opposite phase to the potential supplied between the starting electrodes I and 5 of the main discharge device I, to accomplish this purpose.

The operation of the apparatus is illustrated in Fig. 3. In this view, the full-line sine curve 53 represents the control potential supplied by the oscillator 33 to the auxiliary discharge device 35. The broken-line sine curve 55 represents the control potential supplied between the starting electrodes 1 and 5. It will be noted that the full-line and the broken-line curves 53 and 55 are in opposite phase. The potential difference impressed on the capacitor I3 is represented by the full-line curve 51 rising above the sine curves. If the resistance in series with the capacitor I3 is comparatively small, the capacitor may be charged during the interval corresponding to a single half-wave of the potential supplied by the oscillator 33 as illustrated. During the succeeding half cycle, suflicient current is transmitted between the starting electrode I and the mercury pool of the main discharge device to energize the main discharge device I and the main discharge device having been energized, the capacitor I3 is discharged.

A rectifier 59 is connected between the anode 3 and the cathode 5 of the main discharge device I to prevent the current in the main discharge device from oscillating. The cathode 5| of the rectifier 59 is connected to the anode 3 of the main discharge device I and the anode 53 of the rectifier is connected to the mercury pool 5. If there is a tendency to oscillate, the rectifier network absorbs the oscillations.

In theapparatus shown in Fig. 4, the capacitor I3 connected between the anode and the cathode of the main discharge device is charged during a predetermined interval of time and after it has been so charged, it is discharged during a later interval of time.

For this purpose, an auxiliary discharge device 35 similar to the discharge device utilized in the modification shown in Fig. 2 is provided in series with the power source 34 and the capacitor I3. The cathode 39 of the auxiliary discharge device 35 is connected to the plate 43 of the capacitor I3 that is to be charged positive and the anode 31 is connected to the source. Normally, the discharge device 35 is in non-conductive condition by reason of the functioning of a biasing battery 65 connected between the cathode 39 and the control electrode 4I which maintains the control electrode M at a negative potential relative to the cathode 39. The control electrode 4| is moreover connected to a brush 61 which contacts a through a second brush I3.

As the commutator is rotated, the first brush 51 comes into contact with the segment II for a predetermined interval of time and during this interval of time, the control electrode 4| is at the same potential as the 'cathode 39. The discharge device, therefore, passes current to charge the capacitor I3. The total resistance in series with the capacitor is comparatively low and the capacitor is charged in a short interval of time.

-To ignite the main discharge device I, a second commutator 15 mounted on'the shaft II of the commutator and rotating in synchronism is provided. The second commutator I5 is provided with a conducting segment I9 which is directly connected to the starting electrode I. A brush 8| in contact with the surface of the commutator I5 is connected to that plate 43 of the capacitor I3 which is charged positive through a suitable impedance 93. The impedance properly regulates the starting impulse of current when it is transmitted.

The conducting segment I9 on the last-mentioned commutator I5 is displaced in phase with respect to the conducting segment 'II of the firstmentioned capacitor 69. It operates when contacted by its brush M to discharge the capacitor I3, after it has been charged, through the starting electrode I and the mercury pool 5. The charge on the capacitor. I3 is not exhausted by the impulse transmitted through the starting electrode I and the residual diflerence of poten tial is of sumcient magnitude to cause the main discharge device I to become energized. When the main discharge device is energized, the starting electrode circuit is shunted out. It will be" seen from the above description that a small portion of the charge on the capacitor is utilized to ignite the discharge device after which the residual charge is utilized in producing the main discharge. A single capacitor serves the double function of providing starting current and discharge potential. The periodicity of the discharge produced in the main discharge device may be varied by varying the speed of the commutators 69 and I5.

In the apparatus shown in Fig. 5, the capacitor I3 connected between the anode 3 and the cathode 5 of the main discharge device I is charged through a half-wave rectifier 95 from an alternating source 34. To discharge the capacitor I3 through the starting electrode I, an auxiliary discharge device 2|, similar to the discharge device utilized in the embodiment shown rimary 89 of which is connected across the secondary 9I of the main power supply-transformer 93. However, the terminals of the primary 89 of the auxiliary transformer 81 are so arranged with respect to the terminals of the secondary 9| of the main transformer 93 that the potential supplied in the control circuit of the auxiliary device 2| is displaced in phase with respect to the potential supplied by the secondary 9I of the main transformer.

In Fig. 6, the operation of theapparatus is illustrated graphically. The full-line sine curve 95 represents the potential supplied by the main transformer 93 and the broken-line sine curve 91 represents the control potential supplied by the auxiliary transformer. Since the resistance in series with the capacitor I3 and the halfwave rectifier is small, the capacitor I3 is quickly charged during the half cycles during which the potential output of the main transformer 93 is such that rectifier 85 is conductive. The dot-dash curve 99 represents the charging operation. After the capacitor I3 is charged and the charging operation is discontinued, the control potential supplied to the auxiliary discharge device 2| attains a value of sufficient magnitude to energize the auxiliary discharge device. The capacitor I3 is then discharged through the discharge device 2| and through the starting electrode I of the main discharge device I. The main discharge device I is immediately energized under the influence of the residual potential diiference impressed on the capacitor and it remains energized until the capacitor is discharged. After this, the capacitor is recharged and the process is repeated. It is to be noted that here again a single capacitor I3 is utilized for the double purpose of supplying starting current and ignition potential.

Our invention has been herein shown and described as utilizing a main discharge device I in which the cathode is a mercury pool. The principal advantage of such a discharge device resides in the intense cathode spot which forms on the surface of the cathode when the discharge device is energized. Discharge devices having cathodes of other types have been utilized by us and on the surface of {the cathode in certain of these discharge devices a cathode spot also forms. We have found this is particularly true of discharge devices'in which the cathode is composed of such metals as cadmium, zinc, sodium, potassium, or alloys of these metals. In the claims which follow, we shall refer to a discharge device having a mercury cathode or a mercury pool cathode. ,We intend by this expression to cover the general case of a cathode on which a cathode spot forms and the expression shall be taken to include cathodes of all types on which a cathode spot forms.

Although we have shown and described certain specific embodiments of our invention, we are fully aware that many modifications thereof are possible. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims.

We claim as our invention:

1. In combination an electric discharge device having a, principal current path defined by a plurality of principal electrodes and a starting currentpath extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor including another discharge device having a plurality of principal electrodes and a control electrode, means for normally applying a potential between said control electrode and one of the said last named principal electrodes of such character that the said last named discharge device is deenergized and means for intermittently applying a potential between saidcontrol electrode and the said last-named principal electrode such that the said last-named discharge device is energized for a predetermined interval of time and during said interval of time transmits a pulse of current to charge said capacitor, and means for connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and current flow is initiated in said principal path.

2. In combination an electric discharge device having a principal current path defined by a plu- I rality oLprincipal electrodes and a starting current path extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor including another discharge device having a plurality of principal electrodes and a control electrode, means for normally applying a potential between said control electrode and one of the last said principal electrodes of such character that the last said discharge device is deenergized and means for periodically applying a potential between said control electrode and the last said principal electrode such that the last said discharge device is energized for a predetermined interval of time and during said interval of time transmits a pulse of current to charge said capacitor and means for periodically connecting said capacitor after it has been so charged to said starting path whereby a pulse of current trode, means for normally applying a potential between said control electrode and one of the said last-named principal electrodes of such character that the said last-named discharge device is deenergized and means for periodically applying a potential between said control electrode and the said last-named principal electrode such that the said last-named discharge device is energized for a predetermined interval of time and during said interval of time transmits a pulse of current to charge said capacitor, means for periodically connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and a current flow is initiated in said principal path and means for varying the periodicity of the charge and discharge of said capacitor.

4. In combination an electric discharge device having a principal current path defined by a plurality of principal electrodes and a starting current path extending from a starting electrode for initiating current fiow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor, said means including an alternating source of potential and rectifying means connected in series with said capacitor in such manner that said capacitor is charged only by half waves of said alternating potential transmitted by said rectifying means, means for connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and current flow is initiated in said principal path, said means including another discharge device having a control electrode and a plurality of principal electrodes, means for impressing a first potential between said control electrode and one of the last said principal electrodes, such that the last said discharge device is normally maintained nonconductive, and means coupled to said sourcefor impressing a second potential between said control electrode and the last said principal electrode which is in opposite phase to the pulses of current transmitted by said rectifying means to charge said capacitor.

5. In combination an electric discharge device having a principal current path defined by a plurality of principal electrodes and a starting current path extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor, said means including an alternating source of potential and rectifying means connected in series with said capacitor in such manner that said capacitor is charged only by the half waves of said alternating potential transmitted by said rectifying means, means for connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and current flow is initiated in said principal current path, said means including another discharge device having a control electrode and a plurality of principal electrodes, means for impressing a first potential between said control electrode and one of the said last-named principal electrodes such that the said last-named discharge device is normally maintained non-conductive, and means coupled to said source for impressing asecond potential between said control electrode and the said last-named principal electrode which is in opposite phase to the pulses of current transmitted by said rectifying means to charge said capacitor, and means for varying the frequency of said source of alternating potential.

6. In combination an electric discharge device having a principal current path extending from pacitor including another discharge device having a plurality of principal electrodes and a control electrode, means for normally applying a discharge device is energized for a predeterminedinterval of time and during said interval of time transmits a pulse of current to charge said capacitor and means for connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and current flow is initiated in said principal path.

7. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting current path extending from a starting electrode for initiating current flow in said principal path, an electrode composed of mercury, said starting electrode being composed of a material of the igniter type, a'. portion of which is normally immersed in said mercury electrode, a capacitor connected across said principal path, means for charging said capacitor including another discharge device having a plurality of principal electrodes and a control electrode, means for normally applying a potential between said control electrode and one of the said last-named principal electrodes of such character that the said last-named discharge device is deenergized and means for periodically applying a potential between said control electrode and the said last-named principal electrode such that the said last-named discharge device is energized for a predetermined interval 0! time and during said interval of time transmits a pulse or current to charge said capacitor, means for periodically connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and current flow islinitiated in said principal path and means for varying the periodicity of the charge and discharge or said capacitor.

8. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting current path extending from a starting electrode for initiating said discharge, an electrode composed of mercury, said starting electrode being composed of a material of the igniter type, a portion of which is normally immersed in the last said mercury electrode, a capacitor connected across said principal path, means for charging said capacitor, said means including an alternating source of potential and rectifying means connected in series with said capacitor in such manner that said capacitor is charged only by half waves of said alternating potential transmitted by said rectifying means, means for connecting said capacitor after it has been so charged to said starting path whereby a pulse of current is transmitted through said starting path and current flow is initiated in said principal path; said means including another discharge device having a control electrode and a plurality of principal electrodes, means for impressing a first potential between said control electrode and one of the said last-named principal electrodes such that the said last-named discharge device is normally maintained non-conductive, and means coupled to said source ror impressing a second potential between said control electrode and the said last-named principal electrode which is in opposite phase to the pulses of current transmitted by said rectifying means to charge said capacitor.

9. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting current path extending from a starting electrode for initiating current flow in said principal path, an electrode composed of mercury, said starting electrode being of material of the igniter type, a portion of which is normally immersed in said mercury, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate,

a second electric discharge device of the arclike discharge type arranged to require a predetermined potential to be impressed thereacross to energize it, means for connecting said capacitor, said second discharge device and said starting'path in series, whereby when said capacitor is charged to a predetermined potential, said second discharge device, the latter is energized, a current is transmitted through said starting path, and current flow'in said principal path is initiated, said current flow being discontinued after a predetermined interval of time, and means for adjusting the rate of charge of said capacitor to such a magnitude that the periodicity of initiation and discontinuance of said current flow has a predetermined value.

10. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting path extending from a starting electrode for initiating current flow in said principal path, an electrode composed of mercury, said starting electrode being of a material of the igniter type, a portion of which is normally immersed in said mercury, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate, a second electric discharge device of the arc-like discharge type arranged to require a predetermined potential to be impressed thereacross to energize it, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged 6 a to impress said predetermined potential across said second discharge device, the latter is energized, a current is transmitted through said starting path, and current flow in said principal path is initiated.

11. In combination an electric discharge device having a principal path extending from a principal electrode, a starting path extending from a starting electrode for initiating current flow in said principal path, an electrode composed of mercury, said starting electrode being of a material of the igniter type, a portion 01 which is normally immersed in said mercury, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate, a second electric discharging device of the arc-like discharge type arranged to require a predetermined potential to be impressed thereacross to energize it, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged to impress said predetermined potential across said second discharge device, the'latter is energized, a current is transmitted through said starting path and current fiow in said principal path is initiated.

12. In combination an electric discharge device having a plurality of electrodes at least one of which is composed of mercury, and another of which is a starting electrode and is composed of a material 01 the igniter type, a portion of which is normally immersed in said mercury, defining a principal current path and a starting current path for initiating current flow in said principal path, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate, a second electric discharge device of the arc-like discharge type, means for connecting said capacitor, said second discharge device and said starting path in series, whereby' when said capacitor is charged to a predetermined potential, said second discharge device is energized, a current is transmitted through said starting path, and current flow in said principal path is initiated, said current flowbeing discontinued after a predetermined interval of time, and means for so adjusting said second discharge device that it becomes energized when a predetermined potential difference has been impressed on said capacitor, the magnitude of said potential diiference being such that the time requiredfor charging the capacitor has a predetermined magnitude.

13. In combination an electric discharge device having a plurality of electrodes at least one of which is composed of mercury and another of which is a starting electrode and is composed of a material of the igniter type, a portion of which is normally immersed in said mercury, said electrodes defining a principal current path and a starting current path for initiating current flow in said principal path, means for supplying a potential across said principal path, a capacitor, means including a resistor for charging said capacitor at a predetermined rate, a second electric discharge device of the arc-like discharge typearranged to require a predetermined potential to be impressed thereacross to energize it, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged to impress said predetermined potential across said second discharge device, the latter is energized, a current is transmitted through said starting path, and a current flow in said principal path is initiated, said current flow being discontinued after a predetermined interval of,

time, and means for varying the magnitude of said resistor to adjust the rate of charge of said capacitor to such a magnitude that the periodicity of initiation and discontinuance of said current flow has a predetermined magnitude.

l4. In-combination an electric discharge device having a plurality of electrodes at least one of which is composed of mercury and another of which is a starting electrode composed of a material of the igniter type. a portion of which is normally immersed in said mercury, said electrodes defining a principal current path and a starting current path for initiating current flow in said principal path, means for supplying a potential across said principal path, a capacitor, means including a resistor for charging said capacitor at a predetermined rate, a second electric discharge device of the arc-like discharge type arranged to require a predetermined potential to be impressed thereacross to energize it, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged to impress said predetermined potential across said second discharge device, the latter is ener gized, a current is transmitted through said starting path, and current flow in said principal path is initiated.-

15. In combination an electric discharge device having a plurality of electrodes at least one of which is composed of mercury and another of which is a starting electrode composed of a material of the igniter type, a portion of which is normally immersed in said mercury, said electrodes defining a principal current path and a starting current path for initiating current flow in said principal path, means for supplying a potential across said principal path, a, capacitor, means for charging said capacitor at a predetermined rate, a second electric discharge device of the arc-like discharge type, said second discharge device having a control electrode and a plurality of principal electrodes, means for impressing a substantially constant potential difierence between said control electrode and said principal electrodes, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged to a predetermined potential, said second discharge device is energized, a current is transmitted through said starting path and current flow in said principal path is initiated, said current flow being discontinued after a predetermined interval of time, and means for adjusting the potential impressed between the control electrode and the principal electrode to a value such that said capacitor has been charged to a predetermined difierence of potential, the magnitude of said potential difierence being such that the time required for charging the capacitor has a predetermined magnitude.

16. In combination an electric discharge device having a plurality of electrodes at least one of which is composed of mercury and another of which is a starting electrode composed of a material of the igniter type, a portion of which is normally immersed in said mercury, said electrodes defining a principal current path and a starting current path for initiating current flow in said principal path, means for supplying a potential across said principal path, a capacitor,

means for charging said capacitor at a predetermined rate, a second electric discharge device of the arc-like discharge type, said second discharge device having a control electrode, and a plurality of principal electrodes, means for impressing a substantially constant potential difierence between said control electrode and said principal electrodes, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged to a predetermined potential, said second discharge device is energized, a. current is transmitted through said starting path, and a discharge in said principal path is initiated.

17. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting path extending from a starting electrode for rendering said principal path conducting, an electrode composed of mercury. said starting electrode being of a material of the igniter type a portion of which is normally immersed in said mercury, a capacitor connected across said principal path so that current flows in said principal path under the action of the potential of said capacitor when said path is rendered conducting, means for controlling the potential impressed on said capacitor, and means cooperative with said controlling means for supplying current to said starting path to render said principal path conductive at predetermined times.

18. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting path extending from a starting electrode for renderingsaid principal path conductive, an electrode composed of mercury, said starting electrode being of a material of the igniter type a portion of which is normally immersed in said mercury, a capacitor connected across said principal path so that current flows in said principal path under the action of the potential of said capacitor when said path is rendered conductive, means,

including an auxiliary electric discharge device having a control electrode and a plurality of principal electrodes, for controlling the potential impressed on said capacitor and means cooperative with said controlling means for supplying current to said starting path to render said principal path conductive at predetermined times.

19. In combination an electric discharge device having a principal current path defined by a plurality of principal electrodes and a starting current path extending from a starting electrode for initiating current flow in said principal path, a capacitor connected between said principal electrodes, means for charging said capacitor, including another discharge device having a plurality of principal electrodes and a control electrode, means for normally maintaining said lastnamed discharge device deenergized and means for intermittently applying a potential between said control electrode and the said last-named principal electrode such that the said last-named discharge device is energized for a predetermined interval of time and during said interval of time transmits a pulse of current to charge said capacitor, and means for transmitting a pulse of current through said starting path after said capacitor has been charged to initiate current flow through said principal path under the action of the potential of said capacitor.

20. In combination an electric discharge device of the immersed ignition electrode type having a plurality of principal electrodes and a control electrode immersed in one of said principal electrodes, a capacitor, means for connecting one plate of said capacitor to said one of said principal electrodes, means for connecting the other plate of said capacitor to said other principal electrode, switching means for connecting the last-mentioned plate of said capacitor to said control electrode, and means for charging said capacitor.

21. In combination, an electric discharge device of the immersed-ignition-electrode type having a plurality of principal electrodes and an ignition electrode disposed in contact with one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a current path for supplying ignition current between said control electrode and said one principal electrode and including a capacitor, means for charging said capacitor to one polarity, means for connecting said capacitor across said principal electrodes, said path including means for initiating a discharge of said capacitor therethrough after it has been charged as aforesaid whereupon said device is rendered conductive and said capacitor is further discharged through said principal electrodes.

22. In combination, an electric discharge device of the immersed-ignition-electrode type having a plurality of principal electrodes and an ignition electrode disposed in contact with one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a capacitor, means for charging said capacitor to one polarity, a current path for supplying ignition current between said control electrode and said one principal electrode including said capacitor, means for connecting said capacitor across said principal electrodes through an inductive reactance and means for initiating a discharge of said capacitor through said path, whereby said device is rendered conductive and said capacitor is further discharged through said principal electrodes and inductive reactance.

23. In combination, an electric discharge device of the immersed-ignition electrode type having a plurality of principal electrodes and an ignition electrode disposed in contact with one of said principal electrodes, current of substantial magnitude being required between said ignition electrode and said one principal electrode to render said device conductive, a capacitor, means for charging said capacitor to one polarity, a current path for supplying ignition current between said ignition electrode and said one principal electrode including said capacitor and means for connecting said capacitor across said principal electrodes, said capacitor being effective after charging to cause current flow through said path whereupon said device is rendered conductive and said capacitor is discharged through said principal electrodes.

24. In combination an electric discharge device having a principal current path extending from a principal electrode, a starting path extending from a starting electrode for initiating current flow in said principal path, an electrode composed of mercury, said starting electrode being of a material of the igniter type, a portion of which is normally immersed in said mercury, means for supplying a potential across said principal path, a capacitor, means for charging said capacitor at a predetermined rate, a second electric discharge device of the type having an abrupt characteristic arranged to require a predetermined potential to be impressed thereacross to energize it, means for connecting said capacitor, said second discharge device and said starting path in series, whereby when said capacitor is charged to impress said predetermined potential across said second discharge device, the latter is energized, a current is transmitted through said starting path, and current flow in said principal path is initiated.

DEWEY D. KNOWLES CECIL E. HALLER- DISCLAIMER ,2,310,0 92NDewey D. Knowles, Forest Hills, Pa., and Cecil E. Holler, Bloomfield,

J. ELECTRIC DISCHARGE. 'APPARATUS. Patent dated Feb. 2, 1943.

Disclaimer filed Mar. 15, 1945, by the assignee, Westinghouse Electr'io (if Manufdcturing Company. Hereby enters this disclaimer to claim 19 of the said patent.

[Ofic'ial Gazette April 17, 1945.]

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