US2469357A - Electric discharge lamp system and method of operation - Google Patents

Description

H. K. BOURNE 2,469,357 ELECTRIC DISCHARGE LAMP SYSTEM AND METHOD OF QPERATION Filed om. 1946 May 10, 1949.

A. C. SUPPLY CIRCUIT INVENTOR: HARRY KEBBELL BOURNE,

HIS ATTORNEY Patented May 10, 1949 ELECTRIC DISCHARGE LAMP SYSTEM AND METHOD OF OPERATION Harry Kebbell Bourne, Rugby, England, assignor to General Electric Company, a corporation of New York Application October 8, 1946, Serial No. 701,966 In Great Britain December 27, 1939 Section 1, Public Law 690, August 8, 1946 Patent expires December 27, 1959 3 Claims.

My invention relates to electric discharge lamp systems and more particularly to systems and methods of operating electric discharge lamps intermittently or periodically.

I-Icretofore it has been suggested to produce intermittent flashes of light by the utilization of an electric discharge device, or lamp of the high pressure metal vapor type, and periodically shortcircuitin an impedance in series with the lamp so that the power output is periodically increased thereby causing the luminous output of the lamp to rise and produce light flashes of large luminous output. The prior art arrangements have been deficient particularly with respect to the fact that no provision is made for assuring that the lamp is pre-conditioned to furnish the large luminous output when subjected to irregular or uneven time patterns such as that encountered in sending flashes of light for signalling by code.

It an object of my invention to provide a new and improved system for operating electric discharge lamps.

It is another object of my invention to provide new and improved methods of operating electric discharge lamps intermittently.

It is a further object of my invention to provide new and improved systems for pro-conditioning and preheating electric discharge lamps whereby uniformity of light output at high levels may be obtained even though the lamp is subjected to irregular or uneven time patterns of operation.

Briefly stated, I provide a new and improved system for operating electric lamps, such as electric discharge lamps of the high pressure metal vapor type, which require predetermined initial temperature and pressure conditions in order to produce a desired luminous output. For example, in electric discharge lamp systems intended for operation to produce periodic or intermittent light flashes, it is desirable that means be provided to assure adequate heating of the discharge lamps not only initially but also during the intervals of time between the flashes even though the flashes occur in irregular or uneven time patterns. Accordingly I provide, in a system for obtaining intermittent flashes of light, means for intermittently or periodically shortcircuiting an impedance in series with the lamp to increase the power input to the lamp while maintaining the arc discharge in the lamp during the simmering periods of reduced power input. More specifically, the system is arranged to transnut to the lamp a predetermined minimum value of simmering current, which may be defined as a value of current suitable for maintaining an arc 2 discharge therein. Provision is made to increase the value of simmering current transmitted to the lamp to a value greater than that existing during the periods of reduced power input and less than that existing during periods of increased power input, when the period of reduced power input is in excess of a predetermined time. In this manner, the lampis pre-oonditioned so that the lamp rapidly produces high level luminous output upon increase of the current supplied thereto. Where the lamps are of the filamentary type, electrode or cathode heating means may also be employed to provide constant heating current to the filamentary cathodes thereby supplementing the preheating and pro-conditioning effeet as described hereinbefore.

For a better understanding of my invention reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. The single figure of the drawing illustrates an embodiment of my invention as applied to a circuit for operating a lamp intermittently from an alternating current supply circuit. 7

Referring now to the drawing, I there illustrate one embodiment of my invention as applied to a system for intermittently or periodically operating an electric discharge lamp 1 at relatively high levels of luminous ouput. The lamp I is preferably of the high pressure metal vapor type, such as one employing mercury vapor, and may include electrodes 2 of the filamentary type which are supplied with a predetermined value of heating current through transforming means 3 energized from a suitable source of current, such as an alternating current circuit.

In order to limit or control the current transmitted to the lamp I from the supply circuit I provide impedance means which may comprise a single multi-tapped reactance or which comprise serially connected reactors 4, 5 and i2. This impedance means serves a plurality of functions one of which is the establishment of a predetermined minimum value of simmering current to maintain an arc discharge within the lamp l during periods of reduced power input. Another function is the transmission of increased values of current to operate the lamp at high levels of luminous ouput upon short-circuiting of predetermined parts thereof by elements described hereinafter. A third function is thetransmission of a second value of simmering current greater than that existing during the periods of reduced power input and less than that existing during periods of increased or high power input.

As a means for increasing the current transmitted to lamp I in response to a predetermined circuit controlling operation, I provide an electroresponsive device or relay having an actuating coil and contacts 6 which short-circuit reactors 5 and I2. Relay 1 may be initiated in its operation by an initiating means or key 8 which is connected in series relation with the actuating coil of relay 1 across the supply circuit. Contacts 6 of relay 1 are normally open.

As an agency for modifying the action of the relay 1 when the interval of time between succeeding periods of operation thereof exceeds a predetermined value I provide a time delay electro-responsive device or relay 9 having an actuating coil and normally closed contacts I3 which short-circuit reactor I2. Relay 9 may be connected as shown to be responsive to the voltage appearing across the actuating coil of relay I wherein a unidirectional conducting device or rectifier I I is connected in series relation with the actuating coil of relay 9. The time delay operation of relay 9 is obtained by charging condenser I connected across the actuating coil in series relation through device I I and by the discharge of the capacitance I0 through the actuating coil. More particularly, relay 9 is adapted to operate simultaneously with relay 1 upon closure of key 8. Reactors and I2 are short-circuited by relay 1 so long as its contacts 5 are closed. Contacts I 3 of relay 9 remain open so long as the interval of time between successive operations of key 8 do not exceed a predetermined Value. However, if this time interval does exceed this value the discharge current of condenser IIl through the actuating coil of relay 8 decays to a value which die-energizes the relay closing its contacts I3 thereby short-circuiting reactor I2 independently of the operation of relay I. In this manner by virtue of the reduction in the value of the serially connected impedance, the current transmitted to the lamp I is increased to a value greater than the simmering current but less than the current transmitted thereto during high level operation.

Concerning the operation of the system, upon energization of the supply circuit heating current will be supplied to the electrodes 2 of lamp I, and the value of this heating current remains substantially constant with constant supply circuit voltage. Due to the presence of the reactors 4, 5 and I2 a predetermined value of simmering current is supplied to lamp I.

When the system is used as a signalling system, for example in the transmission of code, key 8 will, of course, be depressed intermittently for difierent periods of time with different intervals between succeeding periods of operation. When key 8 is depressed, relay 1 operates imme diately, and its contacts 6 are closed thereby short-circuiting reactors 5 and I2. Relay s also operates immediately and simultaneously with relay 1, being energized by rectified current from the supply circuit through device II. The opening of contacts I3 of relay 9 thus prepares for the connection of reactor I2 in series with the lamp when relay 1 is de-energized in the opening of key 8 if the delay between times of operation becomes excessive. Due to the fact that relay "i short-circuits reactors 5 and I2, a much larger current is transmitted to lamp i. Condenser Iil becomes charged and by virtue of the discharge path thereacross and the incident flowing current through the actuating coil, the relay 9 is 4 held closed so long as the key 8 is pressed periodically providing that the interval between successive closures is not too large. If the key 3 is released for a short period of time, for example, greater than the length of time between words in a message, condenser [0 becomes discharged and the rela 9 is de-energized allowing the contact I3 to close and causing the reactor I2 to become short-circuited. Therefore, the simmering power supplied to the lamp is automatically increased as compared to the simmering power between rapidly occuring flashes. By thus increasing the simmering value of the current during periods between signalling flashes it is ensured that the lamp is ready for immediate operation, while at the same time the ratio of the luminous output of the lamp during flashes to that during the intervals between flashes is increased.

If the above described system is to be operated on direct current, then of course the impedances may be resistances, but the electrical circuit affording the time delay feature will operate on either alternating or direct current. It is within the purview of my invention that other types of time delay circuits such as thermionic grid controlled electric valves now well known in the art may be used in place of the electro-responsive device or relay 9 and the associated condenser. Furthermore, it will be appreciated that, if desired, the relay 9 may be of the relatively small control type and an intermediate power contactor may be used between relay 9 and the impedance to be controlled thereby.

In one system constructed in accordance with my invention the power supplied to the discharge lamp was 10,000 watts, and the simmering power when the lamp was not signalling was 500 watts. The simmering power during signalling is 300 watts. Under such conditions the ratio of flashing to simmering wattage has been increased from 20:1 to 33:1, and the steady light from the lamp has been reduced to approximately 1000 candlepower, while the flash is approximately 55,000 candlepower.

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

1. A method of producing intermittent flashes of light by utilizing an electric discharge lamp energized from a source of current through an impedance, which method comprises intermittently short-circuiting the impedance to increase the power input to the lamp, maintaining the arc discharge in the lamp during periods of reduced power input, and controlling said impedance to increase the value 'of the current transmitted to the lamp to a value greater than that existing during periods of reduced power input and less than that existing during periods of increased power input, when the period of reduced power input is in excess of a predetermined time.

2. In a system for producing intermittent flashes of light by utilizing an electric discharge lamp, the combination comprising a source of current, an impedance connected in series relation with said source and said lamp, initiating means susceptible of intermittent operation, means responsive to said initiating means for intermittently short-circuiting said impedance, a second impedance in series with the first-mentioned impedance, at time delay means responsive to said initiating means for controlling said second impedance to increase thepower input to the lamp to a value in excess of the reduced power input value and less than that existing during periods of increased power input.

5 3. A method for producing intermittent flashes between succeeding intermittent flashes exceeds of light by utilizing an electric discharge lamp, a predetermined value. which method comprises short-circuiting inter- HARRY KEBBELL BOURNE. mittentiy an impedance in series with the lamp, maintaining an arc discharge through the lamp 5 REFERENCES CITED d rin p ds f reduced power input y hea The following references are of record in the ing electrodes thereof, and short-circuiting a file of this patent;

part of said impedance to increase the power input UNI to the lamp to a value in excess of the reduced v TED STATES PATENTS power input and. less than that existing during 10 Number Name Date periods of increased power input when the time 2,178,423 Inman 1939

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