US2426229A - Electric discharge lamp and starting device - Google Patents

Description

Aug. 26, 1947. H. J. M CARTHY 2,426,229

ELECTRIC DISCHARGE LAMP AND STARTING DEVICE Original Filed Nov. 8, 1941 2 Sheets-Sheet 1 II); .u

- IN VEN TOR. ffENRY J [7 61 1122271 ATTORNEY Aug. 26, 1947. H. .1. M CARTHY ELECTRIC DISCHARGE LAMP AND STARTING DEVICE Original Filed Nov. 8, 1941 2 Sheets-Sheet 2 INVENTOR.

HENRY J M CARTHY AQTORNEY Patented Aug. 26, 1947 UNITED STATES PATENT OFFICE ELECTRIC DISCHARGE LAMP AND STARTING DEVICE- Henry J. McCarthy, Danvers, Mass, assignor to 'Sylvania Electric Products Inc., Salem, Mass, a corpora'tiono'f Massachusetts Griginalapplication November 8, 1941, Serial No. 418,358, now Patent No. 2,346,109, dated April 4, 1944. Divided an 151 this application March 31, 1944, Serial No. 528,973

-1 Claim.

This invention relates to thermal relays and more particularly to thermal relays of the type mal relay capable of delicate adjustment and positive action.

Another object is to provideathermal relayof a basic type capable of several modifications thereby insuring a design for each specialized purpose.

A further'objectlis to provide a thermal relay which will enable the pre-heating of the electrodes of the discharge device inaminimurnperiodof time.

Otherobjects, advantages and features will'be apparent from the following specification taken in conjunction with'the accompanyingjdrawingin which:

Figures 1-7 inclusive consist of a series of circuit diagramanoted with'the letter aiand a corresponding series of schematic diagrams, noted with-the letters 6 and c, of one or more thermal relays in which each circuit may be employed.

Figure 8 is a side elevational view of the thermal relay ofFigure 5.

Figure 9 is a projection 'of the thermal relay of Figure8.

Figure 10 is a schematic diagram of a lampand a circuit with which any one of the several relays of Figures 1-7 may be used.

In the'operation of a fluorescentlamp, it has been 'found necessary to heat the filamentary electrodes thereof for a brief interval in order that they may support the discharge across the lamp. For lamps of the same-size and wattage, theilengthof this heating interval is substantially uniiorm in duration. However, it may Well happen that a certain lamp of the same size and wattage, may require a longer pre-heating interval for the filamentary electrodes thereof than another. With this in mind, I have devised a thermal relay which is so constructed that it will not only initiate a primary pre-heating period but will also provide an number of secondary pre-heating periods necessary in order tostart the lamp.

My invention consistsfundamentally of a bimetallic strip, a.highsresistance rod associated therewith in-a manner toconductheat-to the'bimetallic strip yet insulated therefrom, and a pair of electrical contactsasso'ciated with an end of said bimetallic -strip,-one of said contacts being normally closed with anend of the strip and the other beingfnormally open-with respect thereto.

The first -pre-heating interval is initiated throughthe contact "normally closed with the bimetallic strip. In this way no time is lost by having to wait for the relay elements to assume certain positions before the filamentary electrodes start to heat. In this way they start to heat as soon as the lamp starting apparatus is connected to the line. The length of time it-takes to heat the bimetal sufficiently to cause it to break from its normally closed association with one of the contacts is calculated to be-substantially the same asthat normallynecessaryto heat the filamentar electrodes-sufiiciently to support the discharge across the lamp. This heating of the bimeta'l during the initial pre-heatin'g period is accomplished'through-the contact with which it is normally closed. -I-his contact is .one 0f high contact resistance and-may c'onsistof a heating coil or resistance in heat-imparting relation thereto or it may 'take the lorm'of a carbon contact.

If for any reason the lamp arc fails to strike after this initial pre-heatingperiodthe line voltage, which is across the resistance rod once the bimetal breaks 'from the contact with Whichit is normally closed, will heat the 'bimetal sufficiently to draw it over and close .with the secondelectrical contact thereby initiating the second :electrode .pre-heating period. llhis second period lasts as long as it takes for the bimetal to cool sufficiently to break from its position closed with the "second electrical contact, the strip :starting to cool -as-soon as it closed with the. contact in as muchzas the resistance rod which was imparting the heat thereto is short-circuited by the closing of thetbimetal with the contact.

When this second electrode pre-heating interval has been 'terminated by the breaking .of "the bimetal from the second contact, the lamp -.arc mayormay not strike. 'Ifitdoesnt, line'voltage will again the across the resistanceand another electrode pre-heatin'g period will be initiated as soon-as the heat 'fromthe resistance rod-causes the bimetal to close with the second. electrical contact. 'This'cycle' of operation :will continue until the lamp arc finally strikes.

When the lamp does light, the voltage-across the resistance rod will be about one-half linevoltage,:i. e., about the same asatheyoltage acrossthe lamp. In terms of heat-imparting ability, it means that the resistance rod conducts enough heat to the bimetallic strip toprevent it from cooling to the oint where it will close with'thefirst mentioned electrical contact, yet it does not conduct enough heat to the bimetal to cause it to move over and close with the second mentioned electrical contact. Thus under lamp operating conditions, the free end of the bimetallic strip assumes a position midway between the two electrical contacts.

In the several figures of the accompanying drawing I have shown modifications of the abovedescribed principles both with respect to circuits therefor and the rela in which they may be used.

It should be noted that in that section of the several figures noted with a b or a c, the electrical contacts are denoted by arrow heads. It should also be noted that in cases where both are associated with the same bimetallic strip, one is in front thereof and the other in the rear thereof as shown in Figures 8 and 9.

Figure 8 is a side view of the relay of Figure 5 in which the contact of high contact resistance is carbon. It shows the several elements thereof mounted on the base 8 and supported thereon by the support IT. The carbon contact 3, normally closed with the bimetallic armature 4 is supported on the arm I8 from the strip I9 on which the re-starting contact I is mounted. This strip l9 serves as a compensator to provide for ambient temperature changes and insures the proper relative displacement of the several relay elements. The bimetallic strip 4 is supported from the lead-in wire 9 or electrically connected thereto by the arm I2 and is bent around the resistance rod 2 which may be of about 30,000 ohms resistance, and which is coated with a material capable of rendering it insulated from the bimetallic strip yet capable of conducting heat thereto. The elements 3| and 32 are electrical contacts on the free end of the bimetallic strip 4,

Figure 9 shows more clearly how the several element of the relay of Figure 8 are mounted and the relative positions they assume. As pointed out in the description of Figure 8, the bimetallic armature is electrically connected to the leadin wire 9 through the support I2. These lead-in wires 9 and I run up from the base pins II through the base 8 and preferably through the face of the support I! and up the back thereof and then out through the face thereof again to support the resistance rod 2. The strip I9 may be supported from the lead-in wires ID by the arm 30.

In Figure 1a, the heating coil I is connected in series with the resistance rod 2 and the contact 3 which is normally closed with the bimetallic strip 4. When the line voltage is placed across the circuit terminals 5 and 6, the electrodes of the electric discharge device to which the relay is connected will start to heat. The heating coil I is calculated to heat the bimetallic strip 4 enough to cause it to break from its normally closed position with the electrical contact 3 at approximately the same time that the electrodes of the discharge device have become heated sufiiciently to support the discharge thereacross. If the arc fails to strike, the full line voltage now being across the resistance rod 2, the bimetallic strip 4 will be sufiiciently heated by the heat therefrom to be distorted sufliciently to cause it to move over and close with the contact 1.

Once this closing of the strip 4 with the contact 'I has been established, a second pre-heating of the electrodes of the discharge device will take place. The circuit will then be through the bimetallic strip 4 and the contact '1. Thus the resistance rod will no longer impart heat to the bimetallic strip and the strip will consequently cool, breaking from contact I at approximately the same time that the electrodes of the discharge device are calculated to have been heated suiliciently to support the discharge thereacross. If the arc strikes, lamp operating voltage will be across the resistance rod 2. Since this is about half line voltage, the heat from the rod 2 will heat the bimetallic strip enough to prevent it from returning to its initial position closed with the bimetallic strip 4 but not enough to cause it to move over and close with the contact I, If the are again fails to strike, the line voltage will be across the resistance rod 2 and the strip 4 will again move over and close with contact I.

Figure 1b shows the elements of the relay of Figure 1a mounted on the base 8 with the leadin wires 9 and I0 electrically connecting the relay to the base pins II. The bimetallic armature 4 is supported from the lead-in wire 9 by the arm I2 and is bent around the resistance rod 2. The contacts 3 and I are supported on the arms I3 and I4 respectively, the contact 3 being disposed on one side of the strip 4 and the contact I on the other side.

In Figure 2a, the heating coil I is connected in parallel with the resistance rod 2 and in series with the bimetallic strip 4. The heat from the heating coil I will cause the bimetallic strip 4 to break from its position normally closed with the contact 3 to terminate the first electrode preheating period. If the lamp fails to light, the full line voltage will be across the resistance rod 2 which will then heat the bimetallic strip 4 enough to cause it to close with the contact 1 to provide a second electrode pre-heating period. This second period is terminated when the cooling strip 4 breaks from its position closed with the contact 1. The heat from the heating coil I, during operation of the lamp is enough to keep the bimetal 4 from returning to its original position closed with the contact 3 whereas the heat from the resistance rod 2 is not enough to close the bimetal 4 with the contact 1 under lamp operating conditions.

Figure 2b shows the elements of the relay of Figure 2a. mounted on the base 8 with the leadin wires 9 and I0 electrically connecting the relay to the base pins I I.

In Figure 3a, the heating coil is mounted on the bimetallic armature 4 and has the insulating member I 5 disposed therebetween at a point adjacent the contacts 3 and I. Thus at the end of the initial pre-heating period the bimetal 4, the heating coil I and the insulating member I5 will all move as a unit breaking away from the normally closed position with contact 3. If the lamp arc fails to strike, the line voltage now across the resistance rod 2 will heat the strip 4 enough to cause it to move over and close with the contact I and thereby initiate a second electrode preheating period. Figure 3b illustrates schematically the manner in which these elements may be assembled.

In the relay of Figure 4a, the heating coil I is connected in series with a second bimetallic strip l6. This insures more positive breaking of the bimetallic strip 4 from its normally closed position with the contact 3 for the heat from the heating coil I will tend to distort the strip I6 in one direction and such heat as passes to the strip 4 through the contact 3 on the strip IE will tend to distort the strip 4 in the opposite direction. When the strip 4 breaks away from the contact 3 the initial pre-heating period is terminated thereby. If the lamp arc fails to strike, the full line voltage now across the resistance rod L. will heat the strip 4 enough to cause it to close with the contact "5 and initiate a second pre-heating period. Figure 4b is a schematic diagram of the relay using the circuit of Figure 4a.

In Figure 5a, the heating coil I through the contact 3 will heat the bimetallic strip 4, normally closed with the contact 3, sufiiciently to cause the bimetal 4 to break from the contact 3 and terminate the initial electrode preheating period. The second preheating period is imparted if the lamp arc fails to strike the first time when the bimetal 4 is drawn over to close with the contact 1 by the heat imparted thereto by reason of the full line voltage being across the resistance rod 2. The relay of Figure 5 is similar to that shown in my U. S, Patent No. 2,285,450 which issued June 9, 1942.

The elements of a circuit of this type may be arranged as shown in b or c of this figure, Figure 5. heating coil 5 may be wound around the resistance rod 2 as shown in b or it may take the form of a contact of high contact resistance such as carbon as shown in c.

In Figure 641, two bimetallic strips, 4 and, i5, are employed, strip 4 being connected in series with the heating coil l and normally closed with the contact 3 operating to control the first electrode pro-heating period while bimetal l5, heated by the full line voltage across the resistance rod 2 in case the lamp arc fails to strike after the first heating period moves over and closes with contact '3 to initiate the secondary pre-heating period. The heating coil may join the two bimetallic strips 4 and [6 as shown in Figure 61) or it may be wound around the resistance rod 2 as shown in Figure 6c.

The operation of the circuit as shown in Figure 7a, depends on the differential heat between the heating coil 5 and the resistance rod 2. The heat from the coil is enough to cause the bimetallic strip 4 to break from the contact 3 to terminate the initial electrode pre-heating period but it is not enough to cause it to stay closed with the contact I after the secondary electrode pro-heating period has elapsed. Figure 7b shows how the elements of the relay may be assembled in accordance with the circuit of Figure 7a.

In Figure 10, the lamp 20 with the filamentary electrodes 2! and 22 sealed at each end thereof may have a filling of an inert gas such as argon and a vapor such as mercury sealed therein. The

lead-in wire 23 from one end of filaments 2! may be connected to one end of the power line from which the apparatus is operated. An end of the filament 22 may be connected through a suitable ballast impedance such as an inductance coil 24 through the lead-in wire 25 to the other end of the power line. The other ends of each filamentary electrode may be connected together by the lines 263 and 2'5 through the relay 23 which may be of a construction similar to any of those shown and described above. A condenser 29 may be placed across the resistance rod 2 to cut down radio interference due to the operation of the lamp and switch. A condenser of .096 microfarad has proven to be advantageous.

This is a division of my co-pending application Serial No. 418,358, filed November 8, 1941, issued April 4, 1944, as U. S. Patent No. 2,346,109.

What I claim is:

In an electric gaseous discharge lamp circuit having a ballast impedance in series connection with a two-filament discharge lamp, said series connections to said lamp being made to one end of each filament; a bimetallic strip connected to the other end of one of said filaments; a resistance rod in heat-conducting relationship with said bimetallic strip yet insulated therefrom, said resistance rod connecting one end of one filament to one end of the other filament; and a pair of electrical contacts connected together and to the other end of the other filament through low resistance paths, one contact being normally closed with an end of said bimetallic strip when the circuit therethrough is unenergized, and the other contact being normally spaced from said bimetallic strip but adapted to be engaged thereby upon distortion of said bimetallic strip when the circuit through said bimetallic strip is energized.

HENRY J. MCCARTHY.

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

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