US2492750A - Fluorescent lamp starter - Google Patents

Description

Dec 27 i949" J. P. HUNTER 2,492,750

FLUORESCENT LAMP STARTER Filed aan. 1s, 1947 Invent o1- James P. Hunter,

b3 www His Atorweg.

Patented Dec. 27, 1949 James P. Hunter.. Stratford.. Conn. assigner to General.' Electric Company, a. corporation of NexviYnrk" 18, 1947;,.SerialN01- 722.8251

I Cl'ai'm. (Cl. 17d-320).'

The present. invention.r` te apparatus for startingv fluorescent lampsl1 particiilarlyy lamps having at least one electron emitting. cathode.

Starters. for fluorescent.lampsasheretofore-proposed.- includea. switcmwhiclr may be. ot the. glow tube type, for openingthe circuitt the electron emitting. cathode so..- that a..leighyoltagev impressed across the. lampy from. aballast device to start the arc. inthef lamp. In. other prior. arc starters, the starting switch unit: includes. not only the. startingswitclrbut also aloekoutswitch by which the starting switch.is.rendered. inoperative after it has.A madea,y number of unsuccessful attempts. to start the lamp. In some; casesl the lockout switchv is; manually reset.. but. in:y others: it is automatically resets Theliockautfswitch mechanismusually includes athermal element such. as a bi-metallic strip carryineacontact--which coopcrates with. afixed Contact.. If theilamp, fails to start, the. twov contacts are separated by the,y bi.- metal-licv strip whichA is heated.. locally supplied heat produced by theiiow of. current1 throughy a resistor.

It is an:` object ofv my invention toN provide` an improved automatic.4 reset starter whichlisvinexpensive to manufacture, and. extremely: accurate and reliable inA operation.

The above and.4 other objects of invention will best be. understoodffrom the followingidescription taken in.Y connection. with.- the. accompanying drawing in which. Fig.. l. showssa complete starter in front elevation.. withT the.. enclosingA can' in.v seetion; Fig. 2 shows an end elevation of the device showninzf Fig. 1;; Figtr is a rear elevation of the device shown in Fig. 1; Fig. 4 is a section taken along the line; [-4I.irrEig;. It. andF'g. 5 is a schematic element and circuit diagram ot the starter according to my invention.

As shown on the drawing, the starting device comprises asuitable enclosing can Ii, closed at the bottom by a plate of. insulating material. 2 in which. are mounted connection pins. 3= and 4 whereby the` device is connectedlinto circuitwith the fluorescent lamp 5'. Perpendicnlarly mounted on the basel is a supportA B'oiinsulatingrmaterial. On one side of the supportrtheref are mounted. a starting glow switch 'IQ andv a: capacitor 8l. An L-shaped. birmetallic strip 9 is also mounted;A on the support by means of-` two rivets IIL` and. I-I passing through holes in one-arm. of thef. L.. The other arm of the elemente' ishorizontally disposed and, is free to bend and tomove perpendicularly tothe plane of the.- support 6. For this purpose apart of the upper portion ot the sup.- port G is cut away as showninEig. 3. At the free end of the element 9 there'is secured a contact element; I2, preferably off a.: precious metal; such as silver. which may beim firm a.. short piece of wire secured to the bi-metallic element 9 by spot welding. The contact I2 is arranged 2; to. cooperate with` asimilar contactv I3 secured. to the main loi-metallic thermalm member I-t which ismountedon the-opposite sidefof. the supporting plate. G. as by'rivet. I5. and-by rivetZIl.

The bi-metallic element Ill is. primarily actu.- atedy by heat-v generated by a low ohmic. resistor Iwhich may be of the kind described. inPatent No. 2,391,680 of Leonard Wl` Cook, issuedDecember 25 1.945, and vassigned toA thesame= assignee as the present application. As. described. in-v that patent, the resistor L6. may comprise. a low ohmic resistance coil wound on a-core of low heatconductivi-ty which is connectedto the-thermal mem.- ber by a member having good. heat conductivity and which provides a restricted path forl the transfer of heat from.` the core to the thermal member. This thermal conducting. member is shown in- Fg. 3 at I'I..

The thermalv element I4 may further be oper.- ated.v by heat produced by a holdouty heater I8 which. comprises.v a high ohmic resistance. device. According to my invention I prov-ide for direct thermal` conduction of thel heat produced.` by the resistor I8-to the; thermal. element. I4 at the rivet ZIJ.V To this end I prefer to make.- the resistor I8 of. carbonzor other high resistance'heating material with. highly thermally conductive. metal leads one ofwhich serves as a metallic heat conducting element. t9 which is welded. orsoldered. to the element Ity at the rivet 2li or is. otherwise secu-red tothe element I-t toprovide goodthermal conductivity between the resistor I8 and the thermal element' If. This lead I9 is very short which resultsi-n highconductivey eflcency'since little heat is dissipated by air conductioncr radiation.

shownl in Figures. 2; 3 and 4 of the drawing; the lead I9.- is noti substantially longer than the resistors diameter. Thethermalconducting element Ill.` simultaneously'. serves to. make-- an electrical connection between the'resistor.v IVI? and the thermal.rv element I 4i The electrical connections: of; the various.. elementsv are. shown iri'iig; 5. and the operationV of the device will be clear therefrom. When the line switch is closed;y current will initially. 'ow through: the first. lamentin theiiuorescent lamp 5I through` the: glow switch 1;. through. the bimetallic. strip 9;. the'. cooperating: contactsr I2" and lf3 which are normally` closed; .thefbi-metallc vstrip I4;,. resistorn I6., thev second lamentz of the; lamp 5, to the other side of; thelin'e; After a predetermined; period. of time.. the resistor t6. produces suflici'enti heat.v which. is. conducted through. the conducting'member` I7" to thea biemetallic strip I4, tm cause' the strip- I4 toxdei'ectcontact. l3-r awayfrom` contact I2; thereby. opening the starting circuit. Normally, the arein-` the lamp 5I. will` then start under the. influenceV of thefhighvoltage-producedby the ballast in.I the circuit.. however; the lamp fails to start the bi-metallic strip I4 will cool again, thereby closing contacts I2 and I3 to repeat the starting cycle. It will be observed that while contacts I2 and I3 are open and the lamp has not started, substantially full line .voltage appears across the high resistor I8. After several starting cycles during which the lamp has failed to start, suflicient heat will be produced by the resistor I8 to maintain the bi-metallic element I4 continuously in a exed position after the heat from resistor I6 once opens the contacts, thereby continuously keeping contacts I2 and I3 open and preventing reoccurrence of the starting cycle. This condition will persist until the defective lamp is removed from the circuit and a new lamp is substituted or the line switch is opened.

Since the resistor I8 is always across the line while there is a defective lamp in the circuit and the line switch is closed, there will be a continuous current flowing in the circuit. In order to make the energy loss small, it is, therefore, important to make as eicient use as possible of the heat generated by the resistor I8, This aim is achieved by my arrangement of providing direct thermal conduction between the resistor I8 and the thermal element I4.

The use of the direct thermal conduction element I9 has another advantage which makes possible an improved accuracy in the operation of my starter. 'I'his consists in making possible the elimination of bends or corrugations in the bimetallic strip I4 which, it will be noted, is a simple hat strip not formed in any way. By the avoidance of all bending, no stresses are set up in the bi-metallic strip. I have found that as a consequence the amount of deflection of the strip for a given amount of temperature change is substantially constant. Another advantage of making the thermal element I4 in the form of a straight strip of bi-metal is that each strip in routine manufacture will be found to be the same within very close tolerances so that individual calibration of these elements is not required in order to attain the desired accuracy of operation.

In order further to secure accurate operation in spite of ambient temperature changes, I have provided a compensating bi-metallic strip 9 which carries the contact I2 which cooperates with the contact I3 on the main bi-metallic strip I4. The main bi-metallic strip I4 is intended to be deilected only by reason of locally generated heat produced by the resistors I6 and I8. It will, however, in a slight measure deflect in response to ambient temperature changes. While such deiiection might not be suiiicient to open contacts I2 and I3 even with contact I2 firmly fixed, such ambient temperature deflection tends toproduce a variation in the contact pressure which in turn tends to give rise to an inaccuracy in the operation of the starter. My invention avoids this by providing the compensating bi-metallic strip 9, which is, of course, subjected to the same ambient temperature as the main bi-metallic strip I4. Therefore, the contact I2 will be moved in the same direction as the contact I3 is moved by the element I4 in response to ambient temperature changes. It is important in this connection to note the two point anchorage of the compensating loi-metallic strip 9. This anchorage provides the necessary rigidity so that the position of the element 9 will not change with time or due to softening of the supporting member 6 on account of heat which may eventually be developed within the container I. It is also important to note that the compensating bi-metal is on the opposite 4 side of the support from the actuating bi-metal and the local heaters. The compensating bimetal is thus shielded ...from the heat of the resistors and is only affected by ambient temperature.

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

An automatic reset starter for fluorescent lamps comprising a base, an insulating support mounted thereon, first and second terminals mounted on said base and adapted for connection in circuit with the lamentary electrodes of a hot cathode iiuorescent lamp, a bi-metallic strip secured by one end on said support, a movable contact on the free end of said strip, aA cooperating contact supported from said support, a glow switch connested between said cooperating contact and said first terminal, a low resistance time delay heater for heating said strip to open said contacts after a predetermined period of energization of said element, said low resistance heater being electrically connected to said second terminal and connected to the secured end of said strip by electrically and thermally conductive means, a high resistance lock-out heater for heating said strip to hold said contacts open, said high resistance heater being electrically connected by one lead to said strip between said low resistance heater connection and said movable contact and electrically connected by its other lead to said rst terminal, whereby upon the opening of said contacts, said high resistance heater is connected in series with said low resistance heater, said high resistance heater comprising a carbon resistor element having metallic, thermally conductive wire leads in the ends thereof, the said one of which is not substantially longer than the diameter of the element and is fused at its free end directly tol said strip for providing a direct heat conductive connection therewith, the electrical connections to the other lead of said element comprising electrical conductors of lower thermal capacity than the thermal capacity of said strip, and said element being mounted on said support at an'angle to-said strip and extending away from said support, whereby heat transfer from said element to said strip is principally through said one lead.

JAMES P. HUNTER.

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

UNTTED vsTATEs PATENTS Number Name Date 2,128,869 Winborne Aug. 30, 1938 2,294,191 Lord Aug. 25, 1942 2,313,745 Hays Mar. 16,1943 2,332,492 Bensin Oct. 19, 1943 2,333,215 Thomas Nov. 2, 1943 2,341,905 Cook Feb. 15, 1944 2,343,172 Cook Feb. 29, 1944 2,343,262 McCarthy Mar. 7, 1944 2,346,109 McCarthy Apr. 4, 1944 2,352,713 Hodgkins July 4, 1944 2,352,940 Cook July 4, 1944 2,355,476 Smith et al Aug. 8, 1944 2,391,680 Cook Dec. 25, 1945 FOREIGN PATENTS Number Country Date Great Britain Nov. 19, 1925

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