US2379115A - Starting control for electric discharge devices - Google Patents

Description

R. N. THAYER June 26, 1945.

STARTING CONTROL FOR ELECTRIC DISCHARGE DEVICES Filed Dec. 10, 1941 Fig 1.

lnventow" Richard N. Thagev,

His ht'tgr'neg.

uJ ID 0 38a 8 E6,

w wg H H M Mai W Patented June 26, 1945 'STARJIING CONTROL FOB ELECTRIC DISCHARGE DEVICES Richard N. Thayer, Cleveland Heights, one, asslznonto General Electric Company, a corporatlon 01' New Yorlt Application Decemliec 1o, 1M1, Sel'lltl No. 422cm 1 Claim.

This invention relotes to the control of electric discharge devices, and. is especially concerned 7 to be clone several times loclore the (li e classes octucllv For this purpose, cuto= mctic means we commotllv provlclecl which will lllE-tlifi oncl creel: the stertimg @lllillit indefinitely until is occomolislsecl.

Tilt-ouch deterioration in service or as o result oi ccclclent, fiuoi'esceict lomps other dis choice clevlces often or eventually become loco le of stozctiw and zici'mol running, so th toe only effect 01' automatic efifol'ts to s* such a lcmp is continual flashing in it t wt is very enocvlzcs those in the sures, se celves the light of lfilllg lamp, besides uselesslgr weorii'is out storter elevlccc Usually, such incapacity for is due to loss of e c tron emission from cm or electioclec of the lamp, which may test from dissipation 0?. other less of activating cl ml which the emlssioo The object ouol'olc flashing cl sucl'l ls-mp goes on indefinitely, until the power supply is shut oil, or the lcmp removed from Cll'iillillh The purpose of my invention is to obviate the uodesicoole flashing" 'ol clclectlvc lomps without interfering with repetition or? the attempts to start as long t etc clay reasonable prowl ice of success. l3 ccccmplisl'l Wendel stct'tec Ave ogien the starting cult, icrious lectures out"; cclvotitcges of the invention will become oppcrent from the ste SlZf flP/illflll of one species stool form of emlcocli merit, i em the drawing.

the drawing, o cllcgrorm'ootic view of s, fluorescent tulle o2. with circuit (mil sections including my invention, c, mlcbportlotl of the lamp envelope being broken out cool omitted; and Fig, 2 is o tilted or perspective view of starting switch cop-crews suitable for the putposes of my invention, an enclosing casing for the acpemtus being shown broken away.

Fig. 3 is a view similar to Fig. 2 illustrating o difierent term of one of the switches there shown, the casing partly shown in lacing omitted entirely.

I will llrst cle cribs the portion of the cltcuits and apparatus shown wl'ilcli hove heretofore been in use, and which permit the objectionable fissillog of as defective lom'o as described alcove,

1 shows on orclimovv fluorescent tube lamp "in of the positive column electtlc type with o tubular envelope it having spccec.-opo1"t activeteol thermionic ccthoclcs ll, M in its ends, which new Ice speciolly lllllfid cstlioolec oi usuol coiled filament type and owe shown connected cross c oowel supclv citcult lcclucllcc" the cool bsllcst ll, which also sew/cs starting inclcctonce, end the mcrcusl melte cml lcrcclz switch to. The envelope mew cootciio. low" pressure ctmosphei'e of slot cos, such as argon at o pressure cl 2 to 5 mm. of me A" cool also at vocorizclole one; ioislsctlolc wot substonce such we mercury. ll supply oi mer= curs which mov exceed the amount l ll vcporize during opemtiou. oi ,he lcmc cllcoteel by drop ll itislcle the envelope coterl. H is shown connected the elite through the filamentary cathodes ll ll, T stortlng switch El included therein, which mow toe of s thermal type.

The general mode of op lamp L with this circuit arrangement is that when the switch i5 is closest to tutu on thelength of time to preheat the cathodes to on oclequcte emissive temperature, coal there sud olenlv opens the circuit l-l; cool resulting; voltage ltici; across the cathodes it, it sulilccs to initlete discharge between cm-or, in othel: words, starts the lamp.

As shown in Figs 1 and 2, the thermal switch S is of QIOW SWlbCh type, comprising a class envelope 2t containing" c low pressure ctmos pliers oi route sets, such as argon at on absolute psessurc of 25 mm. of mercury. The envelope to may include c. stem 2i through which sealed current leads that are connected to 05% posite sides of the circuit H, and are provided with terminals or electrodes inside the envelope between which a glow dischcme teizes place when the switch it is first closed. The lesol 22 may have an extension (of niclzel, for example) inward or upward from the stem 2| to serve asone terminal, while the other terminal may be formed by the end a U-bent thermostatic bimetal strip member 25 attached to the other lead 23, as by welding, and constituting the temperature-responsive element or the switch 8. The free end of the member 25 lies adjacent the lead 22 to coact therewith both as an electrode for the glow discharge and as a switch contact. For the latter purpose, a contact piece 28 (as o! molybdenum) is shown welded to the free end of member 25. A capacitor or condenser K is shown connected across the circuit H by its leads 28, 29 in shunt with the switch 8, to minimae radio interference as well as arcing between the contacts 22, 28.

The general operation oi such a switch 8 is that when the circuit H is energized as a result of closing the hand switch l5, a glow discharge takes place across the gap between the parts 22, 25. This discharge heats the member 25 until it unbends sufllcientiy to touch the part 22, thus closing the circuit H and shorting out the glow discharge. The thus augmented flow of current in the circuit H continues long enough to heat the filamentary cathodes H, H to an adequate electron-emissive temperature; and by the time this has been accomplished, the thermostatic member 25 cools sufficiently to open the circuit H and start the main discharge between the electrodes II, II, as already described. After the main discharge has started, the voltage on the device S is no longer high enough to maintain any discharge across the gap between the parts 22, 25.

If, however, the main discharge does not start on the voltage kick due to the opening 0! the circuit H by the switch S as Just described, a glow discharge again takes place between the parts 22, 25, and the switch 8 again closes and opens, just as before; and if this effort is not successful in starting the 'main discharge, it is repeatedand so on. If the main discharge cannot be started at all, the lamp L would (with the circuit arrangement and parts so far described) go on to flash in the objectionable manner explained above.

In accordance with my invention, means of control are provided for determining the condition of the circuit H as to continuity in such a way that after reasonable efforts of the starter S to start the main discharge, a condition of circuit H that prevents flashing of the lamp L is established and maintained, independent and regardless of any further action of starter Sindeed, the operation of starter S may be suspended. For my purpose, automatic control means may be employed whose period of operation (as fixed by design and adjustment) is long enough to include whatever number of attempts by starter S may be considered reasonably worth-while; e. g., a period of some seven to ten seconds under favorable voltage conditions, embracing some three to five attempts, say. The action 01 this automatic control need not be an arbitrary matter of fixed adjustments, however, but can be made responsive to the actual'attempts of starter S to start the main discharge.

A simple control for this purpose is shown in Figs. 1 and 2 as comprising a thermal switch T whose contacts 3|, 22 are connected across the starting circuit H in parallel with the starter S, to shunt the starter, but whose heating resistance 32 is connected into the circuit H in series with the starter 8. As shown in Fig. 2, this switch T comprises as its temperature-responsive r connector 31.

element a thermostatic bimetal strip member 34 having one end attached by welding to an anchorage stud 25 upstanding from an insulative disc or base 28, and carrying the contact II (oi molybdenum, for example) projecting from its free end to coact with a contact 22 in the form of a stud upstanding from the base I8. The stud 32 is shown as provided with an external connector 21 (such as a binding post at the other side or the base 38) for connecting it to one side or the circuit H, and the base carries a similar external connector 28 for connection to the other side or the circuit H. The heating resistance 22 is shown as a wire coil wound around the thermostatic strip 24 over a covering or wrapping of heat and electrical insulation fl-such as asbestos paper-which increases the thermal inertia oi the thermostat and its time of operation. One end oi. the heating coil 23 is connected to the external connector 88; its other end is connected to the member 34, and thus to the stud 38; the starter lead 22 is connected to this same stud 38; and the other starter lead 22 is connected to the stud 32 and the other external The condenser leads 28, 22 are shown as connected to the studs 35 and 32 between which the starter S is connected by its leads 22, 23, as Just described.

In starting a good lamp L, the starter S functions in the usual way, just as if the control T were absent; 1. e., its contacts 28, 22 are closed for only some 2 to 4 seconds, and the resultant heating of thermostatic member 34 is insuiilcient to close the control contacts 8|, 22. Of course some current flows through the heater 22 during the glow discharge while the starter switch S is open, but this current is of low value, and the heating effect from it is insignificant. Even it several operating cycles of the starter 8 occur before the lamp L actually starts, the control contacts 3 i, 32 do not close, if the operating time of the control T is long enough. In the case of a defective lamp, on the other hand, the cumulation of heat in the member 84 from full energization of the heater 33 while the starter switch S is closed during repeated cycles 01' the starter eventually closes the control contacts II, 32 and establishes circuit H independently of starter 8. Current then flows continuously in circuit H, without any possibility of interruption or diminution by any action of starter S, and the lamp L ceases to flash.

However, if the circuit H is de-energized (by opening the hand switch I5, or by removing the defective lamp L and replacing it with a good one), and is allowed to remain de-energized long enough for the control thermostat 34 to cool oil fully, the shunt at T will be opened, and the starter S will again be ready to start the lamp in the usual manner.

Fig. 3 illustrates a device also corresponding to Fig. l, but different from that shown in Fig. 2 as regards the switch Ta. Instead of having its parts on whose relative locations its functioning depends mounted on the fiber base disc 38, which is subject to warpage and aflords such limited available room that the thermostat 84 in Fis. 2 must needs be very short, the switch Ta in Fig. 3 is made as a unit structurally independent of the base 36. As here shown, its bimetal thermostatic strip 34a extends parallel with the glow switch S and the condenser K, and may be as long as either of them. The lower end of the thermostat member 34a is clamped by a rivet 48 between insulative side members 4|, 4! such as fiber strips, insulative spacers t2, tit being inter= posed at either side of the member etc. The

metal contact 32a that coacts with the other (free) end of the member Esta is mounted on the upper end of one of the strips or members 6!, ll, where they are positively and fixedly spaced apart by a metal spacer 53. As here shown, the parts 32a and 33 are formed by the upper end of a wire 44 that is laced through adjacent holes in said member 4! and then bent around the upper edge of said member so that its end engages laterally against the upper end of the other member ti. The other end of the wire is is shown con hected to the connector 3?.

In order to dispense with repetitive description, various parts and features in Fig. 3 are marked with the same reference characters as their homologues in Figs. 1 and 2, a distinctive letter being added where such distinction appears necessary.

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

In combination, a starting switch for a gaseous electric discharge device having spaced electrodes, said starting switch comprising a pair of cooperating contacts, means to connect said contacts across said electrodes, means for actuating said contacts to repeatedly seen and cicse them and to leave them open upon initiation a discharge between said electrodes, and en auxiliary thermal switch comprising e pair of coo3ocrating contacts electrically connected in multiple with said starting switch contacts, a heat responsive member carrying one of said auxiliary switch contacts and normally holding it spaced apart from the cooperating contact, a resistance heater arranged to heat said heat responsive member, and means to electrically connect said heater across the electrodes of said discharge device in series with the contacts of both said switches, heater and heat responsive member being in such thermal relationship that the auxiliary switch contacts are closed thereby to shunt the starting switch contacts only after a predetermined time interval during which the starting switch contacts have opened and. closed at least severei times, the heat responsive member autometiceliy opening the auxiliary switch contacts upon cessation of current flow through said heater.

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