US2208386A - Controlled ultraviolet spark - Google Patents

Description

July 16, 1940. F. E. NULL CONTROLLED ULTRAVIOLET SPARK Filed Sept. 2, 1958 WITNESSES INVENTOR .Fay' E. Vill BY m, Mr

ATTORNEYS Patented July 16, 1940 UNITED STATES PATENT OFFICE 2,208,386 CONTROLLED ULTRAVIOLET SPARK Fay E. Null, Ridgefield, N. J. Application September 2, 1938, Serial No. 228,179

This invention relates 3 Claims.

to a device for producing ultraviolet sparks and has for an object to provide a device where the spark or sparks may be controlled.

Another object of the invention is to produce a device wherein a high voltage spark may be obtained with a constant intensity when over a period of time In the accompanying averaged longer than one second.

drawingever, the usual spark moves back and forth erratically in space and usually presents a zig zag irregular length path. by reason of the noise It also is objectionable produced and is otherwise objectionable unless enclosed in a metallic housing. In the present ing terminals may invention two or more sparkbe used with high voltage (100,000 volts) without objectional actions on the terminals or electrodes and without noise. Also,

according to the present invention a high voltage spark may be produced whose intensity is constant when averaged over an appreciable period of time,

ment (tungsten,

as for instance, for more than one a line spectrum of-the eleetc.) used for electrodes is produced with a strong, continuous background. As the continuous background is weak compared with the strong lines desired intense line emission, the

the rest of the spectrum by means of a filter.

The narrow spectral range selector is sufficiently pure for many processes and experiments. While the device may be used for various purposes, it

is particularly valuable tensity of light sources in controlling the inthat are ordinarily subject to considerable variation, such as sparks and arcs. The spark source produced by repeatedly discharging a condenser across a gap a series of very intense but very light.

consists of brief flashes of When such a light source is used for bactericidal action or as a catalyst in chemical reactions its effect depends in general upon the average light energy leaving and does not depend upon given out steadily or short intense flashes.

the source per second whether the light is is emitted in the form of The device embodying the invention does not attempt to control the intensity of each flash but keeps the energy of the light emitted by the flashes in any .1 of a second the same iskept constant as that emitted in any other .1 the average light intensity hen this average istaken over can readily be separated from time intervals long relative to the duration of a single flash. One of the great advantages of keeping the average light intensity approximately constant lies in the fact that it may be duplicated whenever desired. Referring to the accompanying drawing, it will be seen that wiring for securing a regulated spark of a desired intensity has been illustrated. A part of this wiring includes a condenser and a sparking device for projecting a line of light in a To desired direction. As indicated in the drawing, the wires l and 2 supply alternating current from any desired source at a desired voltage, as for instance, volts. This line voltage leads directly into a condenser charging circuit A. As- 16 sociated with this circuit are three other circuits, namely, a timing circuit B, an input shunting circuit C and a control circuit D. All these circuits coact so that by adjusting the variable resistance 3 in the control circuit D the light in- -2 tensity from the spark may be maintained constantly, as hereinafter fully described. In order that this may be fully understood the various circuits will be described. From the drawing it will be seen that the line voltage impressed across the variable choke l, across the fixed choke 5 and across the primary 6 of the transformer 1 whereby current is induced in the secondary 8 which has its ends connected respectively to opposite sides of the condenser 9. When I the, 30 voltage in condenser is high enough it jumps the gap l0 and thereby produces a spark which gives off an intense light. Part of the light from this spark strikes the cell l l (which is a photosensitive cell) and generates a current which passes in series through the primary I2 of a. transformer l3. This induces a current in the secondary it of transformer I3 which latter current passes to the A. C. amplifier l5 which is connected by two output transformers l6 and I1 to the timing network in the timing circuit B. v

This network produces a D. C. voltage across the resistance l8 which is a function of the intensity of the spark for any desired number of preceding spark discharges. The transformers I6 and [1 are connected in series with the rectifiers l9 and the resistances 20. 'Ihe'secondary leads of the transformers l6 and I1 are connected opposite in phase so that one passes current for the positive part of the amplifieroutput voltage 50 and the other passes current for the negative part of the amplifier output voltage. Thus the current drops across resistances 20 are voltages which depend at any instant upon the intensity of the light received by the cell II at that instant. 55

' erasing the record These voltages across the resistances 20 cause currents to flow charging the condensers 2| through resistances 22. During the part of a cycle during which the voltage across a rectifier I9 is negative, 2i partially discharges through the series resistances 22 and 23,- thus partially of the amplifier output for the immediately preceding half cycle and for What remains of other preceding half cycles. By properly adjusting the capacities and resistances, the memory of the previous current can be integrated so that the voltages across the condensers 2! depend to any desired amount upon the intensities of previous half cycles of the amplifier output. The sum of the voltages on the condensers is impressed upon the rectifier l9 and the resistance 18 in series.

The voltage across resistance 3 is balanced against the voltage across the potentiometer or variable resistance 3 of the controlcircuit D, the resultant voltage being impressed across the grid and filament of the 23, which has a high impedance input. The actuating tube 23 passes a current whenever the intensity of the spark exceeds a certain amount which is determined by the setting of the potentiometer 3. When the actuating tube (thyratron) 23 passes current a voltage is induced in the transformer 25 which is sufiiciently large to make the actuating tube (thyratron) 26 of the circuit C conducting even though the filament-plate voltage on tube 26 may be small at that instant. When current flows in the transformer 27 of the circuit C it acts as a shunt on the transformer l of the charging circuit .A which charges the condenser Q. This'shunting action decreases the voltage across the primary of the transformer 7 by effectively changing the time constant of the circuit and causing the charging time of the condenser 9 to be longer. This results in fewer sparks per cycle and reduces the light energy emitted by the light source per second.

The actuating tube (thyratron) 23 must have a tube 23 a chance to pass current and actuate the transformer 25during every charging cycle of the condenser 9. This is most conveniently accomplished by using the input voltage across the transformer l on the primary of the transformer When this A. C. Voltage induced in the secondary of the transformer 28 is less than the voltage of battery 29,110 current carrfiow through the transformer 28 because of the rectifier '33. If under this condition the tube 23 does not pass current, the voltage across its filament-plate will be equal to the voltage of battery 3i. Then if the filament-grid voltage on tube 23 is now increased until it exceeds the critical value, the tube 23 Will pass current through resistance 2 3. This current will then continue to flow regardless of any change in the filament-grid voltage, until the voltage induced in the secondary of transformer 28 minus the value of the voltage of battery 29 is greater than the current drop actuating tube (thyratron) filament-grid voltage is.

. variable resistance 3 the current is blocked). During the stoppage of the current through tube 23 a voltage is induced in transformer 25which breaks down the actuating tube 26, thus shunting the primary of the transformer 1. By adjusting the relative values of the voltages across battery 29 and transformer 28 it is possible to have this shunting action occur at any desired magnitude of the sinusoidal A. C. voltage Wave across the primary of transformer l. The current through transformer 27 remains blocked until the magnitude of the voltage across transformer 28 has fallen to such a value that the voltage of battery 3| exceeds the current drop across resistance 24. Current will now start flowing through the actuating tube 23 if the voltage impressed across the filament-grid of tube 23 exceeds the critical value, and be blocked through transformer 28 by the rectifier 30. Thus, whenever the current is increased or decreased through tube 23 a voltage is induced in transformer 25. By altering the connection of the secondary leads from transformer 25 it is possible to make the grid of tube 26 positive with respect to its filament when the current through tube 23 is increasing (or decreasing by reversing secondary leads). Tube 26 can only pass current however when the plate is positive with respect to the filament and this only occurs for the positive half of the input input voltage on the lead-in wires i and 2, or

can be built on successive negative half'cycles 0f the input voltage on lead-in Wires i and 2, but cannot be made positive on both the positive and negative halves of the input voltage cycle. As shown in the drawing, the source intensity can only be correct on successive half cycles of one polarity of the input voltage.

When the voltage across variable resistance 3 in the control circuit D is adjusted so that tube 23 passes current during a maximum part of the time, the amplifier output meter M in the timing circuit B has a minimum reading. When the tube 23 does not pass current the reading of the meter M is a maximum. If the voltage across the is adjusted about half way between the two extreme conditions it maintains the average value of the reading of the meter M constant, corresponding to a certain average intensity of light from the spark for when the transformer l is shunted more or less of the time to maintain the average value of light intensity from the spark constant.

I claim:

1. In a device of the character described, a sparking device, a condenser interposed in the circuit rent from said cell for timing the function of said sparking device, and a circuit for controlling the intensity of the spark may be regulated. and the number of sparks in a given time controlled.

2. In a device of the character described, a sparking device, means including a source of alternating current, a transformer .and a condenser for producing a spark in said sparking device, a photoelectric cell positioned to receive light from said sparking device, a shunt input circuit having an auxiliary transformer, said shunt circuit having the primary winding of the first mentioned transformer in series with the primary Winding of the auxiliary transformer for varying the intensity of the spark, a circuit for controlling the action of the first mentioned transformer including the secondary Winding of said auxiliary transformer, a variable resistance and an auxiliary circuit provided with current from said cell, said auxiliary circuit being provided with means for supplying direct current to said variable resistance for holding back current passing therethrough.

3. In a device of the character described, a sparking device, a charging circuit including a source of current, a charging transformer, and a condenser, a photoelectric cell positioned to receive light from said sparking device, a second circuit having a second transformer for controlling the voltage supplied to said charging transformer, the primary winding of said charging and said second transformer being in parallel, an actuating tube positioned in series with the secondary winding of said second transformer, said actuating tube and second transformer acting as a shunt across the charging transformer primary when actuated by a voltage on its gridlament, a second actuating tube for controlling the first mentioned actuating tube, a third circuit provided with current from said photoelectric cell and means for directing current from said third circuit for actuating said second actuating tube.

FAY E. NULL.

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