US2266616A

US2266616A - Electric discharge lamp circuit

Info

Publication number: US2266616A
Application number: US339159A
Authority: US
Inventors: William J Scott
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1939-06-26
Filing date: 1940-06-06
Publication date: 1941-12-16
Anticipated expiration: 1958-12-16

Description

Dec. 16, 1941. w. J. sco'rT ELECTRIC DISCHARGE LAMP CIRCUIT Filed June 6, 1940 Inventor William J 14 64) His Attorney.

Patented Dec. 16, 1941 ELECTRIC DISCHARGE LAMP CIRCUIT William J. Scott, Rugby, England, assignor to General Electric Company, a corporation of New York Application June 6, 1940, Serial No. 339,159 In Great Britain June 26, 1939 3 Claims.

My invention relates to gaseous electric discharge lamp circuits and particularly to such circuits which are adapted for use with electric discharge lamps which at starting require a pre heating of their electrodes. For such preheating of the electrodes it is common to provide the lamp with a short circuiting switch whereby heating current is drawn from the supply line through the lamp ballast and the two lamp electrodes. The ballast employed must have a minimum impedance for the proper control of the lamp during its normal operation but in certain cases this minimum is too large to permit the heating of the electrodes in as short a time as is desired. It is the object of my invention, therefore, to provide an improved circuit by which the impedance of the ballast is decreased when the electrodes are to be heated for the starting of the lamp thereby to shortenthe starting period. My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended vclaims.

Referring to the drawing Fig. 1 is a circuit diagram illustrating one embodiment of my invention, and Fig. 2 is a like diagram showing a modification.

In Fig. 1 of the drawing shows a gaseous electric discharge lamp of the positive column type comprising a tubular envelope having the spaced

electrodes

2 and 3 therein and containing a gaseous atmosphere such as a few millimeters of a rare gas, for example argon, and a small quantity of a vaporizable metal, such as mercury. The interior surface of the envelope may, if desired, be covered with a fluorescent material. The

electrodes

2 and 3 are thermionic being filamentary in form and adapted to be preheated to an electron emitting temperature before the discharge is started in the lamp. The lamp is shown connected with the source of supply 4 of alternating current which, for example, may be a 60 cycle, 115 volt lighting circuit, the connections therewith being represented at 5 and 6. In one of these connections, namely, 5 I have shown the lamp ballast 1. While this may be in the form of a resistor, I prefer to employ a choke coil or reactor because of the economy'in operation obtained therewith. I have accordingly represented the ballastas a reactor having the core 8 upon which is the winding 9. The winding is provided with the intermediate tap whereby the winding is divided into the two parts H and 2, part II being connected directly with one end of the electrode 2. The tap connects with the front contact ll of the switch |5 and the end of the part l2 of the winding connects with the back contact l6 of the switch. The blade of the switch connects with the supply circuit 4, a suitable control switch ll being shown in this connection. Tied to the switch l5 by the insulating link 20 is the lamp short circuiting switch 2| the blade ofwhich connects with one end of the electrode 3 and the fixed contact 22 of which connects with the other end of the electrode 2. This switch may be electromagnetic if desired, but I prefer it to be thermal. For that reason I have represented the switch 2| as a bimetallic strip having the heater 23 adjacent thereto by which the strip is caused to warp in a direction to open the short circuit produced thereby. The heater 23 is shown included in the connection 6 between the other end of the electrode 3 and the source 4. It is so constructed and related to the bimetal strip comprising the switch 2| that when the

electrodes

2 and 3 become heated to an electron emitting temperature the switch 2| will open the short circuit across the lamp and thus cause the lamp to start.

When the circuit is energized by the closing of the control switch H, the two switches being in the closed positions illustrated, heating current is supplied to the lamp electrodes through section II only of the ballast reactor. By reason of the relatively low impedance of this section of the reactor the value of the current supplied to the electrodes is such as quickly to bring them up to an electron emitting temperature. When this is reached the switch 2| operates to open the short circuit causing a discharge to start in the lamp and at the same time operating the switch I5 to include the section 2 of the reactor as well as the section II thereof in circuit with the lamp, the impedance of the entire reactor being that required for the proper operation of the lamp.

Instead of switch l5- serving to open circuit the part l2 of the reactor for the purpose of rapidly heating the electrodes it may, if desired, serve to short circuit that part. Thus the end of part l2 of the reactor may be permanently connected with the switch blade l5 as shown by the line 24 in Fig. 2.

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

1. In combination, a gaseous electric discharge lamp having a plurality of spaced electrodes therein adapted to be supplied with preheating current, a two-part reactor connected in a series of one of the parts of said reactor on said preheating current by cutting out said part and common actuating means for said switches.

2. In combination, a gaseous electric discharge lamp having a plurality of spaced electrodes therein adapted to be supplied with preheating current, a reactor having a two-part winding connected in a series circuit with said lamp to be supplied from a source of alternating current, a switch connected between said electrodes for controlling the preheating current supplied thereto, means for increasing the supply of preheating current to said electrodes comprising a switch arranged in one position thereof to eliminate the eilect of the reactanoe of one of the parts of said reactor in reducing said preheating current by cutting out said part and means for operating said switches substantially simultaneously.

3. In combination, a gaseous electric discharge that side of said source to which the reactor is connected whereby in one position of the switch the current of said series circuit is supplied from said source to one end of said reactor and in another position thereof it is supplied to said tap, and means responsive to said preheating current for actuating said switches.

WILLIAM J. SCOTT.