Dec. 31, 1946. Original Filed Sept. 12, 1940 mumr/o 2,413,363 H.-J. MCCARTHY THERMAL RELAY FOR FLUORESCENT LAMPS ' I Patented Dec. 31, 1943 2,413,363 - A UNITED STATES ‘PATENT OFFICE 2,413,363 I THERMAL RELAY FOR FLUORESCENT , LAMPS - ' Henry J. McCarthy, Danvers, Mass., assignor to Sylvania Electric Products, Inc., Salem, Mass., a corporation of Massachusetts Continuation of application Serial No. 356,566, September 12, 1940. This application January , 1943, Serial No. 471,200 v 2 Claims- (Cl. 200—122) V i. This invention refers to electric gaseous dis charge lamps and in particular to'thermal relays for operating ?uorescent lamps. This applica tion is a continuation of my coepending applica tion Serial No. 356,566, filed September 12, 1940. An object of this invention is to provide ‘a start ing switch for electric gaseous discharge lamps which will permit the cathodes of the lamp to be plil‘eheated before the discharge is started between t em. Another object is to provide a starting switch 9 ported between and connected to the lead-in wires ‘l and t, is also mounted on the mounting plate 2 but on the side opposite the condenser E. The leadn-in wires ‘l and ii of the resistance rod 3 are joined to the lead-in wires 3 of the con denser at'the eyelets d. The joining ofv these two sets of lead-in wires at the eyelets 6 may be done by spot-welding, soldering or somesimilar means. The lead-in wires 3 of the condenser l 10 are projected through the eyelets 4% in the‘rnount ing plate 2 and extend down through the eyelets 9 in the circular base plate illv and into the base will elapse for the of pins 5 where they may be soldered. Although the cathode than is absolutely necessary. .eyelets 4 and 9 are used in the mounting plate 2 A further object is to provide a. switch which 15 “and the base plate l0, respectively, any other will function under all possible conditions of material may be used that will permit a joining starting and restarting, and ?xing of the lead-in wires at these points. Another object is to provide a switch which which will be so timed in its action that no greater interval of time ‘ preheating will be so mounted as to be capable of withstand Eyelets, or some similar means are necessary due to the fact that the base plate and mounting ing accidental, careless or rough usage without are made of Bakelite or ‘some similar in having the precisely adjusted parts thrown out 20 plate sulating material. v“ of alignment. p The supporting arm ll of nickel or some simi A feature of this starting apparatus is that it lar material extends inwardly from the lead-in ‘eliminates the unnecessary time lag present in many switches during the starting and restart 25 wire 71, and attached to the inward end thereof is the bimetallic strip it? which is bent around lng period. the resistance rod 6. Attached to the inner side Another feature of this switch is that it is so of the free end of the bimetallic strip l? is the mounted that even if it were dropped or other low resistance contact 25. The resistance rod wise mishandled, the precisely adjusted parts would not be disturbed. ' Other objects, advantages and features will be apparent from the following speci?cations taken may have thereon an insulating coating ill of, 30 for example, alumina and shellac. ' I have found that an insulating coating of alumina and shellac is best suited for the par in conjunction with the accompanying drawing ticular purpose for which it is herein employed. in which: 2 apply two coats of a dewaxed shellac and then Figure 1 isa ‘front perspective of the thermal two coats of an alumina-shellac mixture. Each relay assembly. coat isbake'd before another coat is applied. Al Figure 2 is a side elevation detail of the thermal though I have‘ used two coats of shellac and two relay. coats of alumina and shellac the number of coats Figure 3 is, a front perspective viewed .from I be varied inasmuch as uniformity of the below of the thermal relay assembly with the 40 may coating is the object to be attained. I have just container partly cut away to show the insulating applied two coats of shellac before applying any alumina because with the shellac foundation a Figure 4 is a schematic wiring diagram of the higher breakdown voltage is obtained. This coat thermal relay. l I ing also prevents the bimetallic strip irom cut— Similar reference characters refer to similar ting through the resistance rod. parts in the several views of the drawing and in The supporting arm I4 of nickel or some slml- ‘ the speci?cations which follow. ' lar material extends inwardly from the lead-in The switch in my invention comprises a con wire 8 and attached thereto and projecting up denser. a resistance rod supported between and wardly and parallel to the bimetallic connected to the two lead-in wires, a bimetallic 60 strip 12 therefrom is the strip IE to which is attached the strip bent around the resistance rod, and a high means. _ . ' andetwo‘lowresistance polnts.. ’ U-shaped arm l6 of nickel or some similar ma-' terial. Attached to one end of this .U-shaped The condenser I is mounted on the mounting arm is the high resistance contact H, which may plate 2, having its. lead-in wires 3- extending beof carbon-and ‘which is normally closed with thrpughthe eyelets 4. The resistance rod 8, sup 55 the bimetallic strip l2. Attached to the other ' _ _ 2,418,868 4 I . the plate 2 and base Ill resides in the lead wires end of the ueshaped arm-is the low resistance contact l8, which may be of silver and which is 3. Resting of plate 2 on base I 0 provides a con normally open in respect to the bimetallic strip ' tact between the plates, but not a connection. l2. This low resistance contact acts as an aux-~ ' iliary starting means for if the ?laments of the lamp have not been suf?ciently heated to start the discharge across the lamp, by the time the The lead wires 3 cushion am! shock received by the base I!) and are rigid enough to act as sup ports and yet resilient enough'to provide cush ioning action for the plate 2 and the various bimetallic strip breaks away from the high re members mounted thereon. ' I The entire switch unit may be inserted in a rod 6 will continue to heat the bimetallic strip l2 10 metal container l9 and may be insulated there and cause the strip l2 ‘to bend back causing the ' from, by‘ a thin tube of insulating paper 22 around the-inner wallof the container l9 and a ' low resistance contact 25 attached thereto, to wafer 21 of insulating material in the top of the touch the low resistance contact l8 thus short container. This container may have several circuiting the resistance‘ rod and starting the pre-_ tangs 20, on the open end which may extend over heating of the lamp ?laments. the base plate l0 after the switch has been in The resistance rod should have a high resist- _ serted in the container. The base plate I0 has ance, say 40,000 ohms. For this resistance I have , sistance contact H, the current in the resistance ' used, for example, a resistance rod, 0.45 inch . several notches 2|, therein, over which the tangs long and 0.65 inch in diameter. For my_high 20 are bent. If these tangs 2!] ever became loose and permitted the base plate to move, the switch ‘would not be affected, for the movement of the resistance contact I have used carbon, having a contact resistance of about 15 to 30 ohms. For my low resistance contacts I have used silver,_ having a resistance of a fractional part of an ohm. Although I have used these particular ma terials, my invention does not necessitate the use of these exact same materials. It' is su?icient switch would be absorbed by the ?exible wires 3 of the condenser, thereby protecting the more sensitive and vital parts of the switch and pre venting them from being thrown out of align-L ment. ance contact points and a high resistance rod be used. A condenser of .006 microfarad across the contacts has proven to be advantageous for the base pins may be ?at or grooved depending on the type of contacts used. If a wire contact is used, I have found that pins with grooved sides provide a ?rmer contact surface. . the base plate I0,-,but is so cut as to be elevated from the base plate at the points-where the con denser lead-in wires 3 extend down into the base If this were not done it would be quite What I claim is: dif?cult to centrally locate the mounting plate 2 on the base plate In and still have the wires 3 _ extending down into the base pins in their proper positions. The base pins may be of the type suit '40 able for use in a socket of the type described in Patent #2,261,170, in my name, and datedNo vember 4, 1941. The manner in which this switch is mounted allows for considerable accidental misuse. . Due to the fact that several of the parts which are, vital tothe operation of the switch are very ?nely proportioned and the slightest change therein would cause ine?ective or ine?icient operation, this switch is mounted in a manner asto have 1 ‘those parts which are not ?nely proportioned and sensitive, absorb the shocks of accidental misuse. The lead-in wires 3 of the condenser I are quite ?exible. Due to this ?exibility of these wires, and the fact that the mounting plate 2 is not ?ush mounted 'on the base plate l0, any move ment or disturbance of the base plate will not disturb the switch elements because the switch _ any desired shape. The contour, as shown in Figure 1, has been selected because it facilitates and makes easier the welding operations on the. thermal relay. The contour of the sides of the elimination of radio interference. The mounting plate 2 is not mounted ?ush on ‘ pins 5. , The contour of ‘the mounting plate may take that a high resistance contact point, low resist ' 1. A thermal relay unit for electric discharge lamps comprising a horizontal rigid base plate of insulating ‘material, arigid thermal switch sup porting plate of insulating material perpendicu lar to said base plate, a U-shaped conductor member of relatively stiff wire disposed in sub stantially parallel spaced relation to said plate and having a high resistance portion in the por- _ tion between its side sections, rigid anchoring means for securing the free ends of said conduc tor member to said thermal switch supporting plate; a bimetallic member in close proximity to said resistance portion, a supporting arm ?xed to one of the side sections of said conductor act ing to support said bimetallic member, a contact member adjacent the free end of said bimetallic member, a supporting arm ?xed to the other side section of the conductor member acting‘ to sup port said contact member, a pair of contact pins ?xed in said base plate and semi-?exible lead wires connected to the points of attachment of the conductor member with said vertical plate acting ?exibly to support said vertical plate and mount as a unit will merely bend forward or 60 the thermal switch thereon from said base plate. backward, the shock being entirely absorbed by i 2. A thermal relay unit for electric discharge the ?exible lead-in wires of the condenser. The mounting plate 2 may rest on the base lamps having the elements de?ned in claim 1 and in which the said vertical supporting plate plate “1 although it is preferably held in spaced relation therewith. The only connection between is I-beam shaped in outline. HENRY J. McCARTI-IY. '