US2342257A

US2342257A - Electric system

Info

Publication number: US2342257A
Application number: US390723A
Authority: US
Inventors: Edgerton Harold Eugene
Original assignee: Individual
Current assignee: Individual
Priority date: 1941-04-28
Filing date: 1941-04-28
Publication date: 1944-02-22
Anticipated expiration: 1961-02-22

Description

Feb. 22, 1944. EDGERTON 2,342,257

ELECTRIC SYSTEM Filed April 28, 1941 INVENTOR Egg-fig? Efdggpim ATTORNEY Patented Feb. 22, 1944 UNITED STATES PATENT OFFICE 2,342,251 ELECTRIC SYSTEM Harold Eugene Edger-ton, Belmont, Mass.

Application April as, 1941, Serial No. 390,723

I 21 Claims. (01. ale-ass) The present invention, though having fields of more general usefulness in electric systems, is particularly related to stroboscopes and to the production of intermittent or flashing light. The present application is a continuation-in-part of application, Serial No. 685,501, filed August 16, 1933.

An object of the invention is to provide a new and improved electric system and a new and improved stroboscope of the above-described character.

Other and further objects will be explained hereinafter and will be particularly pointed out in the appended claims. The invention will now be described in connection with the accompanying drawing, the single figure of which is a diagrammatic view of circuits and apparatus arranged and constructed according to one embodiment of the invention, illustrating a stroboscopic light source operated by alternating current, but capable of operatmg at any flashing frequency.

A- mercury-arc gaseous-discharge-lamp is illustrated as provided with two internal electrodes in a glass tube envelope 2. These tubes are normally non-conductive. The remarks throughout this specification concerning mercury-arc stroboscopes apply equally well to tubes filled with other gases, with or without mercury vapor.

One of the internal electrodes is in the form of a liquid pool 4 of mercury, used for a cathode, and the other serves as the anode B. If, other than mercury-arc tubes are employed, other substances, such as aluminum, barium, iron, etc., or various combinations of elements, may also be employed as the cathode. An external, metallic grid or control electrode I is situated around the glass, outside of the mercury pool 4, opposite to the meniscus of the mercury, and serves as a starting band for facilitating the starting of the tube. Other types of starting bands may be employed. It is also possible to employ an internal grid or control electrode which, like the electrode I00, may be excited from the secondary winding 29 of a transformer of any desired type, such as a flashing, high-ratio, step-up transformer 30. A voltage will be accurately and reliably applied to the primary winding 36 of the transformer 30 from a source of direct-current voltage, so as to be transmitted to the external grid or electrode I00, thereby accurately and reliably starting the mercury-arc tube 2. The source of direct-current. voltage is shown as supplied from a common type of full-wave, thermionic, rectifier-and-fllter circuit, comprising thermionic or gaseous-

discharge rectiflers

20 and 22, connected with any desired source I of alternating energy of suitable voltage and frequency in any well-known manner, as by means of a secondary winding H! of a transformer I48. The secondary winding H1 is shown connected to the anodes of the

rectifier tubes

20 and 22. The conductor In is shown connecting the anode 6 to one end of the secondary winding 1, through the rectifier tube 20. A main discharge capacity or condenser 26 is normally charged to the full potential of the rectifier. A filter condenser 25 is provided as part of the source of direct current, large in capacity when compared to the condenser 25, the function of which is to maintain a supply of energy between the pulses of power given by the

rectifier units

20 and 22 to the load 2.

The cathode 4 and the anode 6 of the normally non-conducting mercury-arc stroboscope tube 2 are connected in the output circuit of the tube 2, directly across the condenser 26, in any desired manner, as by means of wire conductors 8 and I0. A current-limiting, charging impedance 35 is employed, which may be constituted of a wire conductor. This conductor or impedance 35 is usually a combination of resistance and inductance,

and is large enough to hold back the current until the tube has deionized, but small enough to allow the condenser to charge in time for the next flash.

The condenser 26 is charged from the said directcurrent source of voltage by connecting it to the secondary winding i4! through the rectiflers 2c and 22. The series circuit consisting of the impedance 35 and the condenser 26 may be oscillatory, non-oscillatory, or critically damped, as desired; the use of both oscillatory and non-oscillatory condenser charging circuits is already known to the art. The impedance 35 may be chosen so that its resistance and inductance shali have such magnitude relative to the capacity of the condenser 26 that the charging circuit shall be oscillatory. There is nothing critical concerning the charging circuit, however, except when the natural period of the series circuit or the time constant is appreciable when compared to the interval of time between flashes.

The impedance 35 connects the cathode 4 and one end of the condenser 26' to the negative end of the before-mentioned direct-current source of voltage. The impedance 35 may, however, be connected in series with the anode 6, in the positive side of this source. The anode 6 and the other end of the condenser 26 are connected to the positive end of. the direct-current source.

the anode is positive. If the mercury-arc tube 2 has been exhausted adequately, it will not conduct current when the condenser is charged, notwithstanding the difference of potential between the cathode 4 and the anode 6. The usual voltage to which the condenser is charged is from 200 to 2,000 volts.

The quantity of stroboscopic light is determined by the amount of energy in the condenser 33 and by circuit conditions. The capacity of the condenser 23 is increased, as by varying the condenser 23 or by means of additional condensers 21 until there is sufficient average light for the particular frequency of flashing and the extraneous illumination. The additional condensera 21 may be connected by means of switches 3 and I, in parallel with the condenser 26, thus to increase the brightness of flash. Slow speeds require a larger amount of light per flash than fast speeds to give the same average illumination. The amount of light per flash may be varied also by changing the value of a series resistor II in the lamp-discharge circuit, as well as in other ways.

In order to obtain sudden surges of current through the primary winding 36 of the flashing transformer 30, a timing relay is employed. The timing relay is preferably in the form of a normalLv non-conducting mercury-vapor thyratron trigger tube I43, or other gaseous-discharge device, such as a gas-filled hot-cathode thermionic tube, or a grid-controlled cold-cathode arc-discharge tube, connected with the transformer in such a manner that, when it operates, the energy in a small condenser 23 is discharged at selected intervals into the transformer 30, whenever the tube 2 is to be set into operation. As the tube I43 conducts in one direction only, it serves as a check valve. It is a gaseous-conductor device having at least three electrodes, namely, a cathode 43, a grid 03 and a plate 52, and may be of a type in which the maximum potential which can be established between the two main electrodes 43 and 63 without appreciable current flow therebetween may be controlled by controlling the potential between one of the main electrodes, namely, the cathode 43, and the third electrode 33. The current between the anode 33 and the cathode 43 may be controlled, and the electric discharge between them may be imtiated, by varying the potential of the third electrode II with respect to the cathode 43.

The trigger thyratron tube I40 is connected across a bleeder resistor 33, so as to be supplied with voltage therefrom. The bleeder-resistor 33 thus serves as a source of energy for the condenser also. The bleeder resistor 33 is connected. in series with an impedance, which is preferably constituted of a bleeder resistor 31, across the condenser 33, which constitutes the main power-supply for the tube I40. Power for the tube I40 may, however, be obtained, if'desired, from a separate power-supply. The resistors 3I and 33 may be so proportioned that a desired voltage of. say. 300 volts shall appear across the resistor 33. The bleeder resistance 33 allows a small current to flow, in order to maintain the proper voltage bias upon the grid 30 and its resistance is necessary to prevent the self operation of the thyratron I40 when the condenser 28 becomes fully charged. By reason of the connection of the grid 50 to the conductor 8, advantage is taken of the negative bias across the resistor 3| to keep the tube I40 ineffective until an impulse is applied to the grid 50.

The secondary winding 29 of the transformer 301s shown connected in the input circuit of the tube 2, between the cathode 4 and the external electrode I00, to produce the high-voltage triggering action. The primary winding 38 of this transformer is connected, in series with the condenser 28, in the power output or control input or plate circuit of the thyratron I40, between the cathode 48 and the plate or anode 52. The primary winding 36 is thus connected in parallel with the tube I40 but in series with the condenser 20. The power output circuit, while normally dpen, because of a normally negative bias on the grid 50, becomes essentially short-circuited whenever the grid 50 s subjected to a suitable stimulus.

The condenser 28 may be charged from the same direct-current source of voltage, or from any other suitable voltage supply, through the preferably resistive impedance 3 I, in series therewith. The impedance 3i may, however, be inductive, or a combination of resistance and inductance. The

condensers

26 and 28 are both charged from the said direct-current source through the impedance 35, the condenser 23 through the resistor 3i. If the impedance is reactive, or if there are other circuit conditions such that the grid voltage exceeds the critical starting potential, the thyratron circuit may, under certain conditions, generate its own oscillations at a frequency determined by the circuit constants and the characteristics of the tube. The impedance, 3I may be made adjustable,'as illustrated, in order to vary the charging rate of the condenser 28 and this, in turn, regulates the frequency of the 'high-voltagesurges that are applied to the external electrode I00. The impedance 3| of Fig. 1, in addition, prevents a destructive discharge of the condenser 20 through the thyratron I40, in case the stroboscopic tube 2 fails to function. The resistor 33 is made to have a large value, or is disconnected, when selfoscillaticns of the thyratron I40 are desired. The grid 50 may be connected to various taps on the resistance 33 or 3|, to cause the thyratron to oscillate as a relaxation oscillator. In all cases, the grid 50 is normally negative with respect to the cathode 48.

The self-excited relaxation-oscillator thyratron circuit described in the preceding paragraphs as initiating, discharge of the condenser 26 at selected intervals is sometimes termed a self-excited static inverter. This inverter produces electrical impulses at a controlled rate determined by its adjustment. If an external signal is used to trip the thyratron, the circuit is sometimes called a driven static inverter.

The manner of connecting the grid for selfoscillation depends upon the characteristics of the particular thyratron that is used. Thyratrons, furthermore, especially the inverter types that have a short deionization time, require a certain amount of grid current in order to conduct. Often a positive voltage is required on the grid of a negative-control thyratron to supply the required grid current through a grid resistor I42, connected between the controlled grid 00 and the grid-biasingresistor 3i. The grid reslstor I42, if varied, will vary the self-oscillation rate, if grid currents are necessary for starting.

The use of the thyratron tube I40 makes it possible to operate the circuit without any moving parts, except, in some cases, for causing the thyratron to function. The thyratron does not conduct current when there' are no impulses in the grid circuit, except when used for self-oscillation, as described. A timing impulse coming into the input or grid circuit; to stimulate the grid 50, trips the thyratron I40, establishing a high-potential gradient between the electrode I and the cathode 4, thereby causing starting of the tube 2. The time of starting is controlled by the potential on the grid 50.

The flashes of light are illustrated as controlled through the closing of a switch 32 which may, of course, be controlled by a periodically movable member, as described in Letters Patent 2,181,879, issued December 5, 1939. The switch 32 may be very small, sinceit causes very small currents. The grid 50 of the thyratron I40 is connected to one side of the switch 32 through a small trip condenser 59, which may be as small as 0.00025 microfarad. The other side of the switch 32 is connected to the anode 52. The grid 50 is also connected to the negative end of the resistor 3|, in series with the resistor I42. The resistor I42 limits any current that may tend to flow when the grid 50 becomes positive, or when there is any ionization in the tube. When the switch 32 is closed, therefore, at any time after the voltage across the condenser 26 reaches its maximum value, the grid 50 of the thyratron becomes positive with respect to the cathode 48 to a value greater than the breakdown voltage between the grid 50 and the cathode 48, whereupon the thyratron becomes conductive.

At the instant that the grid potential, in response to the action of the switch 32, reaches the critical value, positive with respect to the cathode 48, in response to the stimulus applied to the grid 50, the output circuit of the thyratron I40 is completed from the anode 52 to the cathode 40, through the primary winding 36 and the condenser 28. The energy stored in the condenser 28 is then suddenly discharged intothe low-impedance primary winding 36 of the stepup transformer 30, through the output circuitof the thy'ratron tube I40. This magnetically induces a high voltage for a brief interval of time in the secondary winding 29. A high voltage is thus suddenly applied to the electrode I00. A surge of current is caused to flow through the resistor I42. The cathode 48 is thus raised to nearly the potential of the anode 52 during discharge, and the grid 50 is given a sudden and very strong negative bias.

This suddenly applied, relatively high voltage produced by the potential on the grid 50 across the terminals of the secondary winding 29 will cause a bright, cathode spot to form on the surface of the mercury cathode 4 and at the junction between the mercury and the inner wall of the glass tube. The gas in the tube becomes thus ionized. The bright spot constitutes a source of electrons in the vicinity of the cathode 4 that supplies electrons for the discharge of the condenser 26 through the tube 2 between the anode 6 and the cathode 4.

An arc discharge is thus abruptly initiated through the-tube 2. A brilliant flash of light is, therefore, produced by the mercury-pool tube 2 when'the condenser 26, after being charged to a certain value, discharges its energy violently and quickly into it at the desired instant, in response to the stimulus produced upon the band electrode I00 by the impulse surge in the secondary winding 28 of the flashing transformer 30. The potential upon the grid 60 controls the time of starting of the violent, electrical transients that are transformed into useful light.

At the instant of discharge, the current surge is naturally very large, over one thousand amperes, and the flash of light through the tube is very intense and quick. The apparent speed of a moving object is thus effectively reduced or stopped, since the object moves an inappreciable distance during the time that the light is on. Because .of the low impedance of the mercury lamp 2, the voltage across the resistor 33 is zero after the condenser 26 has become fully discharged, preventing the condenser 20 from charging again, and allowing the tube to deionize; and the duration of the flash discharge is short, the time taken for the circuit to function from the closing of the contactor 32 to the flash of light from the tube 2 being about 10 microseconds or less, the exact time being a function of the size of the capacity 26, the voltage to which it is charged, the dimensions of the tube, the temperature of the tube, the impedance of the leads 8 and I0 connecting the condenser and the tube, the volt-ampere characteristics of the tube 2, and other factors. Under some conditions, the duration of the flash is less than one microsecond.

Immediately after the condenser 28 discharges, the grid 50 is caused to be very negative with respect to the cathode 48, and, in this manner, the thyratron is preventedfrom starting as the condenser 28 builds up and the anode becomes positive with respect to the cathode.

The impedance of the conductors 8 and I0 is useful in extinguishing the arc. As soon as the current in the thyratron circuit stops, the current in the tube 2 will not be established in the,

opposite direction; for, since there is no source of electrons on the anode 6, mercury-arc tubes do not reverse in their normal operation. The are, therefore, becomes extinguished. As the tube 2 permits current to flow only from the anode 6 to the cathode 4, it acts as a rectifier. After the tube 2 extinguishes, the cycle is ready for repetition.

The condenser discharge through the mercuryvapor lamp 2 would be oscillatory except for the fact that the tube 2 is a rectifier. This oscillatory tendency is useful, however, since it assists in preventing a continuous flow of current through the lamp 2 from the before-described direct-current power supply. The condenser 26 is charged with a potential of an opposite polarity after a surge of current flows through the tube 2. A negative voltage is thus put on the anode 6, which helps to deionize the tube.

As the thyratron I40 is a rectifier, the current in the circuit comprising the condenser 28 and the transformer 30 cannot oscillate, although there is a tendency to do so. At the instant that the current stops, due to the oscillation, the tube I40 begins to deionize, since the grid and plate voltages, at this instant, are both either negative or zero with respect to the cathode 48. The charging current of the condenser 28 causes a voltage drop acrossthe resistance 3|, which is negative with respect to the cathode 48. This voltage drop is nearly equal to the voltage of the direct-current supply at the first instant, but becomes smaller as the condenser 28 is charged.

The condenser 24 then recharges from its source of voltage, through the impedance II, in preparation for the next impulse.

The thyratron trip circuit puts a high voltage on the starting band I" ina sudden manner that makes the tube start reliably. The use of this starting-tube thyratron makes the mercuryarc stroboscope a practical and useful arrangement. The mercury-arc tube may thus be started by a few microamperes of current in the grid circuit of the control tube, and there is a negligible time delay between the current impulses to the grid and the starting of the light flashes.

Tripping surges in the grid circuit can be supplied either by transformer or capacity coupling, as commonly used in the art. The resistance Il may be made to have a high value; or it may be open circuited, if self-oscillations are desired.

The gaseous-discharge device I40 is shown connected in circuit with the source of potential and with the variable impedance 33 or Ii. The voltage impulses which occur at the instant that current flows through the electric check valve I40 are, in both cases, conveyed through the transformer 30 to the flash-producing apparatus 2.

A leak resistor I43 may be put across the condenser in the grid circuit to discharge it between successive transients, between flashes, as at the opening of the switch I2, in order to prepare for the next surge, but the value the resistance of the leak is sufliciently high to prevent further influence upon the thyratron if the switch 32 is left in a closed position. The connections may thus be traced from the grid 50, through the blocking condenser 50 and the leak resistor I43, in parallel, the contactor l2, and the primary winding 38, to the anode 52. The trigger tube i4! is thus, through the contactor 32, connected to its grid 50, caused to flash the hashlamp II at the desired instant. After discharge, the grid 50 again becomes negative with respect to the cathode 48.

Once the switch 32 becomes closed, it may remain closed without the tlwratron I40 flashing on again when the

condensers

26 and 24 build up their voltages. The operation is independent of the length of time that the switch 32 remains closed, for the complete function is performed at the moment of first closing.

An adjustable impedance l8, shown as a resistance, is conveniently connected into circuit, especially in variable-speed stroboscopes, as between the cathode 44 and the impedance 3|, for varying the intensity of the starting voltage which is applied to the starting grid Hill. The impedance I9 and the transformer 40 may be in either the anode or the cathode circuit. The impedance i9 is adjusted.until sumcient voltage is obtained to make the operation satisfactory.

The circuits of the present invention are useful for mam! other purposes than for the production of stroboscopic light. They are useful with almost any apparatus adapted for excitation by electrical impulses through the medium of a condenser.

Modifications will occur to persons skilled in the art, and all such are considered to fall within the spirit and scope of the invention, as defined in the appended claims.

What is claimed is:

l. A flash-lamp. system comprising a hashlamp, a first source 01' energy. a discharge condenser, a trigger tube, a second source of energy for the trigger tube comprising a bleeder resistor.

means connecting the flash-lamp to the discharge condenser, means connecting the discharge condenser to the first source of energy to cause the discharge condenser to become charged from the first source of energy, means connecting the second source of energy to the trigger tube to supply energy to the trigger tube, means connecting the trigger tube to the flash-lamp, and means for discharging the discharge condenser through the flash-lamp under the control of the trigger tube.

2. A flash-lamp system comprising a flashlamp, a condenser for discharging through the flash-lamp, a charging circuit for connecting the condenser to a source of energy, a gaseous-discharge trigger device comprising an anode, a cathode and a grid, 9. second condenser, a bleeder resistor for charging the second condenser, means connecting the second condenser to the anode and the cathode, means for controlling the grid to cause the second condenser to discharge through the discharge device, thereby to cause the first-named condenser to discharge through the flash-lamp to eflect flashing of the flash-lamp, and means for reducing the voltage across the bleeder resistor," to substantially zero when the first-named condenser discharges through the flash-lamp.

3. A flash-lamp system comprising a flashlamp, a condenser for discharging through the flash-lamp, a charging circuit for connecting the condenser to a source of energy, a gaseousdischarge trigger device comprising an anode, a cathode and a grid, a second condenser, a bleeder resistor for charging the second condenser, a second resistor, means connecting the resistors in series across the first-named condenser, means connecting the second condenser to the anode and the cathode, and means for controlling the grid to cause the second condenser to discharge through the discharge device, thereby to eflfect flashing of the flash-lamp.

4. A flash-lamp system comprising a flashlamp, a condenser for discharging through the flash-lamp, a charging circuit for connecting the condenser to a source of energy, a gaseous-discharge trigger device, a second condenser, a transformer having a primary winding and a secondary winding, a bleeder resistor, means connecting the bleeder resistor to the first-named condenser to supply energy from the first-named condenser to the bleeder resistor, means connecting the second condenser and the primary winding to the bleeder resistor as a source of energy, means connecting the secondary winding to the flash-lamp, and means for discharging the second condenser through the gaseousdischarge device, thereby causing the first-named condenser to discharge through the flash-lamp.

5. A light-flash producer having, in combination, a gaseous-discharge lamp that 1 mally non-conducting when not in operation and through which, when the lamp is conducting, a discharge may pass to produce a flash of light of substantial illumination intensity, means for connecting the device to a source of energy, means for producing the said discharge from the source when the lamp is conducting, a gas-filled device through which a discharge may pass to render the lamp conducting, a second source of energy for the gas-filled device comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor. and means comprising a condenser for producing a discharge from the second-named sound through the gas-filled device.

6. A light-flash producer having, in combination, a gaseous-discharge lamp that is normally non-conducting when not in operation and through which, when the lamp is conducting, a discharge may pass to produce a flash of light of substantial illumination intensity, means for connecting the device to a source of energy, means for producing the said discharge from the source when the lamp is conducting, a gasfilled device having a control input circuit that is normally unenergized when the device is not in operation and an output circuit through which a discharge may pass to render the lamp conducting when the input circuit is energized, a second source of energy for the gas-filled device comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, and means for energizing the control input circuit.

I. A light-flash producer having, in combination, a gaseous-discharge lamp that is norgas-filled device comprising a bleeder resistor.

means for connecting the bleeder resistor to the first-named source to supply energyfrom the first-named source to the bleeder resistor, means for producing a discharge through the device,

the device having a control electrode that is nornot in operation and operative when effective to render the device conducting to enact a discharge of energy from the source through the device. a gaseous-discharge rectifier that is normally inefl'ective when the rectifier is not in operation and having an anode, a cathode and a control electrode the rectifier being operative when efl'ective to render the normally ineffective means efiective, a second source of energy for the rectiller comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, means for producing a transient impulse upon the control electrode, and means operable in response to the transient impulse upon the control electrode for rendering the rectifier suddenly effective, thereby to render the normally'ineilective means suddenly eilective.

10. An electric circuit comprising a load, a source of energy for the load, a grid-controlled tube, 'means for connecting the tube to the source, means for connecting the load to the tube, means for biasing the grid of the tube, an impedance connected between the grid and the biasing means, a condenser for controlling the said grid connected to the impedance and the said grid, and means comprising a switch for connecting the condenser to a source of energy to cause the condenser to become charged to energize the grid.

11. An electric circuit comprising a load, a

' source of energy for the load, a grid-controlled tube, means for connecting the tube to the source,

' means for connecting the load to the tube, means connected to the impedance and the said grid,

mally ineflective when the device is not in operation for initiating when eilective the operation tion and comprising at, least two principal electrodes and a control member associated with one of the principal electrodes for rendering the electric valve conductive between the principal electrodes. a source of potential, means for connecting the principal electrodes to the source. a capacitance, a-grid-controlled gas-filled electric valve, a second sourceof potential for the gridcontrolled valve comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energyfrom the first-named source to the bleeder resistor, means for charging the capacitor from the second source. and means comprising the grid-controlled valve for transmitting a relatively large transient electrical impulse through said control member and said capacitance to render conductive said first-mentioned electric valve.

9. An electric system having, in combination, a gaseous-discharge device that is normally nonconducting when not in operation, means for connecting the device to a source of energ means normally ineffective when the device is an additional impedance, and means comprising a switch for connecting the condenser through the additional impedance to a source of energy to cause the condenser to become charged to energize the grid.

12. An electric circuit comprising a load, a source of alternating energy, a condenser connected to the source. a filter for filtering alternating-current ripples out of the condenser. a grid-controlled tube, means for connecting the tube to the condenser, means for connecting the load to the tube. means for biasing the grid of the tube, an impedance connected between the grid and the biasing means, a condenser for controlling the said grid connected to the impeditmav constitute a source of energy, means for char ing the second condenser from the bleeder resistor. means for connecting the second condenser to the anode and the cathode to energize the trig er device from the bleeder resistor. means for controlling the control electrode to cause the second condenser to discharge through the trigger device. means for connecting the first-named condenser to the flash-lamp, and means for causing the first-named condenser. after it has become charged, to discharge through the sash-lamp when the second condenser discharges through the trlller device.

14. A lit-fiash-producer having, in combination, a gaseous-discharge lamp that is normally non-conducting when not in operation and through which, when the lamp is conducting, a discharge may pass-to produce a flash of light or substantial illumination intensity, means for connecting the device to a source of energy, means for producing the said discharge from the source when the lamp is conducting, means for rendering the lamp conducting, a second source of energy for the rendering means comprising a bleeder resistor, and means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor.

15. A light-flash producer having, in combination, a gaseous-discharge lamp that is normally non-conducting when not in operation and through which, when the lamp is conducting, a discharge may pass to produce a fiash of light of substantial illumination intensity, means for connecting the device to a source of energy, means for producing the said discharge from the source when the lamp is conducting, a gas-filled device through which a discharge may pass to render the lamp conducting, a second source of energy for the gas-filled device comprising a bleeder resistor, means (or connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, and means for producing a discharge from the second-named source through the gasfilied device.

16. In combination, an electric valve that is normally non-conducting when not in operation and comprising at least two principal electrodes and a control member associated with one o! the principal electrodes for rendering the electric valve conductive between the principal electrodes, a source of potential, means for connecting the principal electrodes to the source, a gridcontrolled gas-filled electric valve, a second source of potential for the grid-controlled valve comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder-resistor, and means comprising the grid-controlled valve for transmitting a relatively large transient electrical impulse through said control member to render conductive said first-mentioned electric valve.

17. In combination an electric valve that is normally non-conducting when not in operation and comprising at least two principal electrodes and a control member associated with one of the principal electrodes for rendering the electric valve conductive between the principal electrodes, a source of potential, means for connecting the principal electrodes to the source, a capacitance, a second source or potential comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, means for charging the capacitor from the second source, and means comprising the grid-controlled valve for transmitting a relatively large transient electrical impulse through said control member and said capacitance to render conductive said electric valve.

18. In combination an electric valve that is normally non-conducting when not in operation, a source of potential, means for connecting the valve to the source, a capacitance, a grid-controlled gas-filled electric valve, a second source or potential for the grid-controlled valve comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, means for charging the capacifor from the second source, and means comprising the grid-controlled valve for transmitting a relatively large transient electrical impulse through said capacitance to render conductive said first-mentioned electric valve.

19. An electric system having, in combination, a gaseous-discharge device that is normally nonconducting when not in operation, means for connecting the device to a source of energy, means normally inefiective when the device is not in operation and operative when eflective to render the device conducting to efiect a discharge of energy from the source through the device, a gaseous-discharge rectifier that is normally inefiective when the rectifier is not in operation and having a control electrode, the rectifier being operative when eilective to render the normally inefi'ective means efiective, a second source oi energy for the rectifier comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, a switch, means whereby manipulation of the switch will produce a transient impulse upon the control electrode, and means operable in response to the transient impulse produced upon the control electrode on manipulation of the switch for rendering the rectifier suddenly effective, thereby to render the normally inefi'ective means suddenly eflective.

20. An electric system having, in combination, a gaseous-discharge device that is normally nonconducting when not in operation, means ior connecting the device to a source of energy, means normally ineffective when the device is not in operation and operative when efiective to render the device conducting to effect a discharge of energy from the source through the device, a gaseous-discharge rectifier that is normally ineffective when the rectifier is not in operation and having a control electrode, the rectifier being operative when eflective to render the normally ineffective means efi'ective, a second source of energy for the rectifier comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resistor, a condenser, means for charging the condenser, a switch, means whereby manipulation of the switch will produce a transient impulse upon the -control electrode, and means operable in reconnecting the device to a source of energy,

means normally inefi'ective when the device is not in operation and operative when efiective to render the device conducting to efi'ect a discharge of energy from the source through the device, a gaseous-discharge rectifier that is normally ineffective when the rectifier is not in operation and having a control electrode, the rectifier being operative when efi'ective to render the normally ineffective means eflfective, a second source of energy for the rectifier comprising a bleeder resistor, means for connecting the bleeder resistor to the first-named source to supply energy from the first-named source to the bleeder resister, a condenser, an impedance in shunt to the condenser, a switch, means whereby manipulation of the switch will produce a transient impulse upon the control electrode, and means operable in response to the transient impulse produced upon the control electrode on manipulation of the switch for thereupon causing the condenser to discharge suddenly through the rectifier to render the rectifier suddenly effective, thereby to render the normally ineflective means suddenly effective.

HAROLD E. EDGERTON.

CERTIFICATE OF CORRECTION. Patent No. 2,5A2,257. February 22, 19th,.

HAROID EUGENE EDGERTON.

It is hereby certified that error appears in the printed specification of the above numbered ,patent requiringcorrection as follows; Page 5, first column, line Claim 5, for the word "sound" read --source--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of 'Hue case. in the Patent Office.

Signed and sealed this 25th day of April, A. D. 191414..

Leslie Frazer (S Acting Commissioner of Patents.