US2538577A - Sparkless camera shutter and flash tube synchronizer - Google Patents

Description

Jan. 16, 1951 c, w. MGCARTY 2,538,577

SPARKLESS CAMERA SHUTTER AND FLASH TUBE SYNCHRONIZER Filed May 8, 1948 Invervh'or" Ctgde W. M CaT- c5,

Patented Jan. 16 1951 "UNITED STATES PA E T OFFICE srAnKI JEss CAMERA SHUTTER. AND FLASH I TUBE SYNCHB-ONIZER Clyde W. McCarty, Lynn, Mass, assignortoGeneral Electric Company, a corporation of New York Application May 8, 1948, Serial No. 25,863

V 1 Claim. (Cl. 95-11.5)

This invention relatesto electric discharge dethrough the enclosed gas. However, ionization vices and more particularly to -a new and immay be increased sufficiently to cause discharge proved apparatus for triggering so-called flash by' sharply increasing the voltage gradient in the @1 v gas, or a portion thereof. Such a voltage gradient Heretofore, there have been devised various 5 increase causes increased ionization since diseiici'tation circuits for controlling the conductivity placement current or condenser charging current of cash lamps. However, these circuits, emin the dielectric consisting of the enclosed gas bodyi'ng switches which employ current-carrying results, whichcurrent causes additional ionizacoiit'acts, could not be used in an explosive attion. This may be accomplished by applying a niosphere, such as exists in a hospital operating voltage pulse between anode 3 and cathode 2. room, for instance. Thus, a sparkless apparatus Discharge in lamp I continues as long as the fortriggering'a'flash lamp is needed for applianode-toecathode'voltage exceeds a critical value cations of this nature. below .which current flow stops. Thus, asource Anobj'ect of my invention is to provide a new of anode-to-cathode voltage capable of supplying and improved igniterexcitationapparatus for. an energyrandof sharply drooping load characteriselectric discharge device. tic, must be provided if, flashes of short duration i Another object of my invention is to provide are desired. Furthen'a large triggering voltage a new and improved sparkless apparatus for trigmust be suppliedflat the instant illumination is gering a photographicgfiash lamp of the gaseous de'sirednu conduction type. I 0 In accordancerwith my invention, lamp I is A further object of myinvention is to provide connected across a discharge circuit 5, 5' which a. new aridimproved apparatus for triggering a may be energized from a 118 volt, 60 cycle source flash l'amp, which apparatus employs amagnet ofcurrent through the primary winding 6 of a secured'to ashutter' of 'a' camera'for actuating transformer l. A manual make-and-break cona control valve which in turn triggers the flash trol switch 8 maybe used to connect transformer lamp. 1 I to the source of current. A secondary winding Further features and advantages of my inven- 9 of transformer I is connected through a rectition will appear from the following description fier I0, and a charging impedance II which may of species thereof. be constituted of inductance or resistance, or

For a better understanding of my invention 30 both, to a capacitance l2. A rectified or direct reference may be had to the followingdescription current source is thus provided for charging the taken in connection with the accompanying drawcapacitance I2 to a voltage, for example, of 2000 ing and its scope will be pointed out in the apvolts. A bleeder resistance I3 is connected across pended claim. The drawing is a diagrammatic capacitance I2, which in turn is in parallel with view of an electric discharge device and a triggerlamp l. A control valve or trigger tube I4 may be ing device therefor incorporating my invention. connected to terminals I5 and I6 of the bleeder Referring to the drawing, I have there il1us= resistance I3, so as to be supplied with a desirable trated one embodiment of my invention as-applied operating voltage therefrom. The trigger tube I4 to an electric discharge lamp I. Lamp I may be may be a thyratron which may comprise an of the cold cathode gas or mercury vapor type evacuated glass envelope II- filled with a suitable which has come into general use, particularly in gas, such as neon, and is provided with a plurality photographic applications, mainly because of its of electrodes, namely a cathode I8, an anode or ability to emit high intensity illumination and plate I9, a control grid 20, and. a shield grid 2I. to reach full intensity almost instantaneously. To terminals I5 and I6 of bleeder I3 there is In addition, lamp I is usually designed to furnish als connected, in series t a capacitance a illumination only during very short increments p y Winding 3 Of a voltage transformer 24. of time and to furnish such a flash at any chosen A secondary winding 25 of transformer 24 is coninstant and at any chosen repetition rate. nected o a triggering coil 26 Wound around en- Lamp I usually comprises a cathode 2 and a velope 4 of lamp I. Control grid 20 is connected anode 3 within a gas-tight vitreous envelope 4 through a resistance 21 to a wire coil 28. A containing a suitable gas such as xenon or argon magnet 29 which, for example, may be a bar or mercury in liquid or vapor form. Electrical magnet three-eighths of an inch indiameter, discharge does not occur when normal anode-tomounted on a flap or door type shutter 30 of a cathode voltage is applied, since ionization re- 5 ca e a 3 s Provided o at e er mains sufiiciently low to prevent breakdown tube I4 upon opening of the camera shutter 30.

the trigger tube Coil 28 is mounted in the path of movement of magnet 29 so that upon opening of shutter 30 of camera 3! the magnet will move into coil 28 which is located near the end of travel of magnet 29. Magnet 29 in turn induces a voltage impulse in coil 29 which is sufficient to cause the tri er tube or thyratron I 4 to fire, the thyratron grid voltage being 'adjusted'so that the voltage generated in coil 28 by magnet-29 is sufficient to cause tube [4 to conduct. The condenser 22 then discharges through the condenser discharge circuit comprising the trigger tube l4 and the primary winding 23 of transformer 24. The resulting high-voltage surge of the secondary winding 25 of transformer 24 is applied to the triggering coil 26 which is wound around the envelope 4 of lamp I. This causes the gas in the lamp I to ionize, permitting the condenser I2 to discharge through lamp I between its electrodes, producing a very brilliant flash of short duration.

Thus, when the entire installation is energized by closing switchS, condenser I2 becomes charged from the direct current source supplied by the rectifier tube 52, trigger tube M being non-conductive. The source of direct current in addition charges'the condenser 22 at the same time. Any time aiter'the voltage across'condens'ers l2 and22 has reached its maximum value, the shutter 3a of camera 31 may be opened and an induced voltage is generated in coil 28 by the action of magnet 29 entering into coil 28. This induced voltage in coil 23 raises the potential of the control grid 2-0 until the breakdown voltage between control grid Zil and cathode I3 is exceeded and M becomes conductive. condenser 22, as heretofore mentioned, then discharges th'rough the condenser-discharge circuit comprising trigger tube It and the primary winding 23 of transformer 24!. The resulting highvcitage surge of the secondary winding 25 or a transformer 24 is applied to the triggering coil 26 of lamp I. This causes the gas in lamp I to ionize, permitting the condenser I2 to discharge through the lamp I, and thus produce a very brilliant flash of short duration. When the con- The I denser I2 is fully discharged, the discharge lamp I promptly extinguishes and the cycle is ready for repetiton.

When the condenser I2 is fully discharged the voltage across the bleeder I3 is approximately zero and thus prevents condenser 22 from charging and, in turn, permits trigger tube [4 to de-' ionize. The time taken for a complete cycle of operation is very brief and the apparatus is again ready for a repetition cycle.

What I claim as new and desire to secure by Letters-Patent of the United States is:

In combination with a gaseous electric discharge lamp having a plurality of electrodes therein, a "current supply circuit, a discharge circuit connected to said electrodes across said supply circuit to effect a flash-producing discharge through said lamp, a starting circuit for supplying a triggering voltage to said lamp at a point on said lamp intermediate said electrodes and comprising a voltage step-up means and a grid controlled electricvalve control means connected to control current flow through said step-up means, a camera, a normally closed flap type shutter mounted on said camera, a magnet mounted on said shutter, and a wire induction coil mounted in the path of movement of said magnet near the end of the path of travel thereof and connected to supply a potential to the grid of said control means sufiicient to render the control means conductive and permit current flow through said step-up means.

CLYDE W. McCARTY.

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

UNITED STATES PATENTS Number Name Date 2,299,497 Rosenthal Oct. 20, 1 942 2,358,796 Edgerton Sept. 26, 1944 2,408,764 Edgerton Oct. 8, 1946

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