US2485520A - Glow discharge switch - Google Patents

Description

Oat. 18, 1949 A. WARSHER I GLOW DISCHARGE SWITCH 2 Sheets-Sheet 1 Filed June 6, 1944 4 INVENTOR Adolf/1 IVQIS/ZQI BY uffllwodw 1' ATTORNEYS Oct. 18, 1949. A. WARSHER 2,485,520

GLOW DISCHARGE SWITCH filed June 6, 1944 2 Sheets-Sheet 2 lNVENTOR Adolph, PVans/zer BY ATTO RN EY5 Patented Oct. 18, 1 949 Adolph War-Sher, Maywoo d J., assignor to Maxwell M; Bilofsky, Newark, N; 'J.

Application-June 6, 1944;Serial No. 538,987

It is among the'objects of thei invention-to provideraglowzdischarge switch, of simple-and rela- =tivelyinexpensive construction, which shall be applicable in ;allrelationswhere'. it i is .desired lautomaticallyxand sensitively toicontrol a circuit in differentiated manner, depending upon the magnitude on heating.- evolvedl by the glow discharge gap, andiniwhich the operationaand; control is effected with'complete safety'eventh'ough the switch .b'e usedr-inenvironmentlwhere explosive gas mixtures 1 may be encountered.

The: invention :has 1 an imp'ortant application to thermionic lampsstantersaof the: glowudis'charge type and intthatl application further and more specialized? obj ectsarea-tozprovide a device of the above type 'which shall readily. be replaceable for the conventional glow: discharge :starter, and which shall in: addition: to its primaryflampsstarting function porformthe adclitional function of promptly and: automaticallyiinhibitingi the interr'mittent flashingof azlamp -t that 1 has .become defective, for' instance, by losstof emissive coating from its electrodes and which shalldo so :withoutz the=:drastic curtailment: in life; incurred ".with themus'e: of conventional glow-discharge ,lswitehes uunder: such intermittent flashing and :yet,-:.under; normal operating; conditions, with a perfect lamp, the starter shall not add: in the least to thewattage'consumed in lamp operation.

Generallyrstated; theinventioninvolves enclos-- xingrin the; hermeticallysealed envelope for the -bimetal: strip -r,usedin' the conventional bimetal v-g-lowswitch starter. for-thermionic devices, a secnd and lessrsensitive thermallyl responsive member:that, upon.sufilcient deflection thereof, effects r a circuit alternative to and distinct fromthat of the normal discharge gap-and in which circuit sufficient heat is evolved to maintain theiaddi- :tional heat responsive :element deflected until the circuit to theswitch-is opened. V

In the accompanying drawings in which are shown one" oremore of variousv possible embodi- ,.mentsof theseveral-features of theinvention,

i Fig. 4. v

i Fig. 6' is-a--viewsimilar to Fig: I 3 of avfurther .modification, and 1 2 plicationof the glow discharge switch as the starter for athermionic lamp.

Referring to :Fig. 1, the switch comprises a hermetically sea'ledienvelope l0, desirably of glass,

.exhausted of air through tube II and charged withnoble gas'such as neon-under very low pressure.

Through the stem Id of the envelope extend the two terminals I2and 13. Upon post l5 ofthe: terminal [2 is affixed themain heat responsive-member, desirably bi-metal'strip l6, which'carries 'a contact ll, adapted to-coact-with montaot [7 upon the end of the companion electrode ISacarried upon post l8.

aiswitching strip, desirably also of bi-metal but less sensitive and more sluggish in-itsresponse to: heat than is the mainstrlp I6, so that in normal o'peration, it remainssubstantially unde- Electrode I 9 is flectedpeven though-strip IE has deflected substantially. Under excessive heat, however, the

"switch-strip I9 isdeflected in the same direction asthe main strip l6. Movable with the switching strip is a contact 20 i normally open, vbut adapted upon-sufficientdeflection of-the switching stri'p'to e'stablishcircuit to an auxiliary electrode 2| which faces the switching strip I9. The

;coritact:2fl-when moved by the defiected switching strip I9 closes circuit through a" connecting wire 22 from the post l5 that carries'the main strip lfi to the auxiliary electrode 2|, which is spaced from switching strip l9 and normally out of circuit. The glow discharge gap G between the switching strip l9 and the auxiliary anode 21 -is designed to have a considerably lower voltage drop than the maindischarge gap G. This is accomplished by providing surfaces with lower workiunctions; as for instance, by coating auxiliary anode 21 with electronemissive material 23am! preferably coating the corresponding face .2 4 is'carried by theupper end of the switching stripv l9 and mounts a glass bead 25 embedding the freeend-thereof. The bead has also embedded thereinbut spaced from'wire 24 .a carrying wire 26 to whichis welded a switching member, desirably in the formofa cross wire 22. In Fig. 1 the switching wire 22 carries the sl 'igw'lais a circuit-diagram showing the ap- 5 contact ZD -at itsinturnedleft.endZ'I. 'The right end 28 of said wire 22 is downturned and has affixed rigidly thereto the auxiliary anode 2| above referred to.

Under normal operation, the heat evolved in glow discharge gap G causes deflection of main bi-metal strip l6, to cause contacts l1 and H to touch, thereby to quench the discharge gap so that the glow discharge switch cools and its contacts |1|1 reopen. However, under any eventual evolution of excessive heat in gap G, the less sensitive switching strip l9 will deflect toward the right, and carry with it the switching wire 23 to bring the contact 28 thereon into engagement with terminal post l5, and thereby impose upon the auxiliary anode 2| the potential of terminal Hi, the switching strip l9 being maintained under the potential of terminal |3. The switching strip in its deflection does not approach the auxiliary anode 2|, since the latter is carried thereby and moves therewith, so that the distance therebetween remains constant. Since gap G has a lower work potential than gap G and the two gaps cannot be maintained in parallel, tn;v glow discharge now is established and maintained across gap G, and gap G is extinguished. The heat evolved in gap G is sufficient, however, to maintain the bi-metal switching strip IS in the deflected position, so that the switch remains in the setting last described until the circuit to the glow discharge switch is interrupted.

Since the oi-metal strips l6 and I9 flex in the same direction, the glow discharge switch is inherently self-compensating and even a considerable increase in the ambient temperature would not cause the contacts l1 and H to touch. It will be understood that wire 22 could be directed to cause contact 28 to engage the bi-metal strip IE or a contact thereon, instead of engaging the rod i as shown.

In the embodiment of Figs. 3, 4 and 5 are shown arrangements utilizing an electric heater in the form of an ohmic resistance, rather than an auxiliary discharge gap, to maintain the switching strip in deflected position after functioning thereof.

In the embodiment of Fig, 3, the post 30 and main bi-metal strip 3| are of conventional construction, as is the coacting contact 32 which, however, is mounted upon a more sluggish bimetal switching strip 33 in turn supported by the second terminal post 34. The contact 32 of said switching strip has in the path of deflection thereof a contact 36 on the end of an electric heater 31 connected by wire 38 to the terminal post 30. Desirably, contact 36 is affixed in insulating relation to wire 38 which is relatively stiff. This may be accomplished by embedding the contact end in a glass bead 39 encompassing and anchored to wire 38. Obviously, under prolonged heat, switching strip 33 is deflected toward the right to close circuit to the ohmic resistance 3i which operates as a heater to maintain the switching strip 33 deflected and to bridge the normal starting gap and does so until the circuit to the switch is opened.

In the embodiment of Figs. 4 and 5, the less heat sensitive bi-metal switching strip 40 which flexes toward the left is mounted on terminal rod 4| and the main bi-metal strip 42 is mounted upon the upper end of said switching strip by an intervening connector rod 43. The main strip 42 flexes toward the right and coacts with a fixed anode 44 on the end of a second terminal rod 45. The latter rod is joined by connector wire 46 to an electric heater 41 near the switching 4 strip 40. The lower end of the resistance 41 is connected to a terminal post 48 insulated as, for

instance, by a glass bead 49 from a wire 50, to

the upper end of which is connected the upper end of resistance 41, the lower end of wire 50 being embedded in said bead at a distance from the bead embedded upper end of wire 48.

As will be apparent, under excessive heat evolution, the deflection of the switching strip 40 toward the left displaces the main strip 42 away from the fixed anode 44, until strip 40 engages the arm 50 of wire 50. Circuit is now established from terminal 4| through switching strip 40, wire 50 and resistance 41 to the opposite terminal 48. The heat evolved by the resistor 41 maintains the switching strip 40 deflected and bridges the gap between strip 42 and anode 44 until the main switch is opened.

In the embodiment of Fig. 6, the terminal post 60 carries the main bi-metal strip 6| of U-form, facing in one direction and the bi-metal switching strip 82 also of U-form but of more sluggish action facing in the opposite direction. The contact 63 of the main bi-metal strip 6| coacts with the anode 64 on the second terminal post 65. The electric heater resistance 61 is near but spaced from switching strip 82 and in the path of movement of the free end thereof.

The lower end of heater 81 is affixed to post 55, the upper end of which is embedded in glass bead 56 in which is embedded the lower end of wire 51 that mounts the upper end of heater 61. Conductor 86 externally of the envelope connects post 65 to post 55. Thus, in operation, when the switching strip is deflected under prolonged heat, it closes circuit to the resistance 61 by engagement of contact 68 on the switching strip with contact 69 upon the upper heater mounting wire 51. The heat evolved in heater 61 is sufficient to keep the switching strip 62 deflected until the main circuit is opened. With the resistance thus in circuit the glow discharge gap between strip BI and anode 84 is bridged by heater 81.

The entire glow discharge switch in each of its embodiments is hermetically sealed in its envelope l0 so that it may be used safely, even in an atmosphere in which explosive mixtures are sometimes present.

In Fig. '1 is shown the circuit diagram of an important application of the glow discharge switch in one of its various uses, i. e., for the starting of a conventional thermionic lamp L with electrode filaments at the opposite ends thereof, each coated with an emissive coating of barium oxide or strontium oxide according to conventional practice.

The glow switch starter S of any of the embodiments shown is in the starting circuit 18, which connects lamp electrodes 1| and 12 in series, for electrically heating the same. An iron core ballast coil 13 is in the line and the lowering of the power factor of the system due to its operation is compensated for by condenser 14 across the line, all in accordance with conventional practice.

In the operation of the conventional glow switch starter, the applied voltage is at the outset suflicient to cause the glow discharge in gap G, but is insufficient to cause arcing of the lamp L. If starter S is of the construction shown in Figs. 1 and 2, the bimetal strip I6 thereof under the heat of the glow discharge, deflects to close circuit to contact |1' while storing energy in ballast coil 13. The glow discharge is thus interrupted with resultant cooling and contraction of the= bimetal strip- H away from contact I'll. As :xa'result-of this openingof the starter: circuit, the

impulse-fromthe-ballastcoil 13 tends torstart therarc inthe lamp Lacross its now= heated electrodes'l l and Hand the starting cycle set forthis 'rres-umed until the arc. in the lamp: L has actually been str-uck and sincesuch arc when once maintained requires voltage less than that. required to initiatethe glow discharge in the "starter -SWibICh S the latter remains outof action.

Should thelampbeco-me defective, as for instance, due-to the loss of emissive material from oneor both of its electrodes, so that the lamp will 'falterinsted: ofmaintaining its arc, the conventional glow switch starter (devoid of the present improvement), would repeat the cycle above set forth andcause the lamp intermittently to flash 1 onan'd ofhto the annoyance of the user and with very-short life of the glow-discharge switch.

With: the glow switch of the presentinvention,

however (illustratively of the embodiment of Figs. 1 and 2), should the glow discharge in gap G bermaintained' for an abnormal length of time, duetotthe slowness in starting or restarting of a defective lamp, the less sensitive bi-metal strip 1 Ma -which in normal operation will not move, is

caused to flex, to bring the switching wire' 22 into engagementwiththe post l5 and to apply the potential of said post upon the auxiliary anode 2|. By reason of the lower work function of the electrodes of glow discharge gap G, the glow discharge is promptly set up betweenzswitching plate I!) and auxiliary anode 2|. The glow discharge in gap G evolves sufficient heat to maintain the bimetalzstrip I9 deflected andlthat glow discharge isthus maintained as long as the main switch 'lfizcontrolling the lamp L is-cclosed.

.Byyreason of its electrodes of lower work function, the existence of the glow discharge across gap G precludes the possibility of the glow discharge resuming across the-main discharge gap G. The intermittent flashing of a defective lamp L is therefore precluded as is the repetition of the cycle of operations of the bi-metal strip I6. Accordingly, the glow discharge switch of the present invention is not subject to rapid wear and will serve for many thousands of hours use.

From the foregoing description, the mode of operation of the glow discharge switches of the embodiments of Figs. 3 to 6, when used as thermionic lamp starters, will be clear without the need for further description.

In each embodiment, it is seen that the use of the present improvement, does not involve the slightest alteration in the mode of operation as compared with the operation of a conventional glow starter switch upon a perfect lamp. The presence of the added safety switching feature does not add in the least to the power consumption as long as the glow starter switch of the present invention is used with a good lamp.

The glow discharge switch in each of its embodiments is, of course, useful as an automatic control switch in a wide variety of applications, in fact, in any relation in which the evolution of heat in the switch, upon exceeding a predetermined minimum is automatically to effect some switching in the circuit connections.

The glow switch starter is a unit of small bulk, in fact in its lamp starter form, it is of bulk so small that there is no need for alteration in the thermionic lamp fixtures now in use that are designed for conventional glow switch starters, to enable replacement of the latter by the im- 6 proved glow switch starter of;- the: present invention.

By the term glow 'discharge.- switch as used in'the claims: ismeant a unit. of the-general; character described, which is charged with anoble gas or mixture: of. noble gases; at pressure; such as to develop. a glow discharge across itselectrodes at voltageacontrolling'a step inthe opera tionof thesystemordevice with. which it.is used.

As many changescould be-made1 in the above construction and: many apparently widely different embodiments of this invention could be made without departing: from the scope-of. the claims, it is. intended that all matter contained in'thea'bove description or shown initheiaccompanying: drawings shall be interpreted aszillustrative and not in a. limiting sense.

Having thus described my invention, what. I claim as new andrdesire to secureby Letters-Patent' of. the United. States is:

1. A glow discharge switch comprising; an: envelopehaving apair of bi-metalrelectrodes spaced for glow discharge therebetween, one'ofsaidxelectrodes being less sensitive'toheat than; the other and flexing away from the latter to serveas; a switching electrode under the prolonged. evolution. of heat in the glowzdischargeegap; am auxiliary electrode spaced from/said. switching electrode'andiout of circuit under .normal operation, and means under controlof said: switching electrode and carried. thereby to close thecircuitto said auxiliary electrode thereby to efiectaglow discharge between the switching and. the auxiliary electrode, said latter glow discharge circuit having suflicient heat evolution tomaintain. the switching electrode in its deflected positionwas longas the circuit remains closed.

2. A glow discharge switch, comprising anenvelope having therein a pair of bi-metal strips spaced for a main. glow dischargetherebetween, terminals carrying the same, one of said strips being of less heat sensitivity than the other, being arranged to deflect away under prolonged heating and constituting a switching strip, an auxiliary electrode movable with and spaced from said switching strip for alternative glow discharge therebetween and having electrodes of lower work function than those of said main glow discharge, and means responding to the movement of said latter strip for electrically connecting the auxiliary electrode with the terminal of the other electrode to initiate the alternative glow discharge, the switching strip being exposed to the heat generated by said alternative glow discharge and maintaining the latter until the circuit to the glow discharge switch is opened.

3. A glow discharge switch comprising an envelope having fixed terminals extending thereinto, bi-metal strips afiixed to said terminals determining a discharge gap therebetween, and having coacting contact portions normally spaced from each other, one of said bi-metal strips being less sensitive to heat than the other and serving as a switching strip upon deflection thereof under prolonged heating, an auxiliary electrode movable with and insulated from said switching strip, said auxiliary electrode and said switching strip being spaced from each other and defining an alternative glow discharge gap therebetween, a connector under control of said switching strip for establishing electrical contact from said auxiliary electrode to the terminal of the other strip, said switching strip being exposed to the heat evolved in the alternative glow discharge gap,

thereby to maintain said switching strip de- 4. A glow discharge switch comprising a hermetically sealed envelope, a pair of electrode posts extending thereinto, a main bi-metal stri rigid at its root with one of said posts, a switching bimetal strip rigid at its root with the other of said posts, said strips being spaced for a main glow discharge gap therebetween, a switching member carried by said switching strip and insulated with respect thereto, an auxiliary electrode carried by said switching member near one end thereof facing but spaced from said switching strip for alternative glow discharge gap having elements of work function lower than those of said main glow discharge gap, said switching member being normally spaced at its opposite end from the electrode post of the main bi-metal strip and closin circuit thereto by the movement of the switching strip under prolonged heat, the heat evolved in the alternative glow discharge gap being sufficient to maintain the switching stri deflected until circuit is opened.

5. A glow discharge switch comprising a hermetically sealed envelope having a pair of bimetal electrodes therein spaced for glow discharge therebetween of higher work function, terminals therefor, said electrodes including a main bi-metal strip, a bi-metal switching strip less sensitive to heat than said main strip so as to deflect materially only under prolonged heat, a switching member carried by said switching strip and insulated therefrom, an auxiliary electrode carried by one end of said switching member, said auxiliary electrode and said switching strip being spaced to define an alternative glow discharge gap therebetween, the other end of said switching member being adjacent the main bi-metal strip and serving to switch said auxiliary electrode into circuit by deflection of the switching strip away from the main strip under applied heat, the heat evolved in the alternative glow discharge gap being sufiicient to keep the switching strip deflected until the circuit is interrupted.

6. The combination recited in claim 5 in which a glass bead wire mounted upon the switching strip mounts the switching member in electrically insulating relation with respect thereto.

7. A glow discharge switch comprising a hermetically sealed envelope having terminal posts therein, a bi-metal main strip on one of said posts, a coacting bi-metal switching strip on the other of said posts, and of lesser rate of deflection than said main strip and a switching wire carried by said switching strip and insulated therefrom, said wire having a downturned end portion, an auxiliary electrode afiixed thereto, facing said switching strip and having an emissive coating thereon, the other end of said wire being movable under the deflection of said switching strip to apply potential from the post carrying the main strip to the auxiliary electrode, the discharge gap to said auxiliary electrode having elements of lower work function than that across the bi-metal strips, the heat evolved in the discharge gap to said auxiliary electrode being suflicient to maintain the switching strip deflected until the circuit is opened.

ADOLPH WARSHER.

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

UNITED STATES PATENTS Number Name Date 2,274,399 Cook Feb. 24, 1942 2,355,476 Smith Aug. 8, 1944 2,367,655 Atkins Jan. 23, 1945 2,372,149 Townsend Mar. 20, 1945 2,408,493 Townsend Oct. 1, 1946 2,427,741 Peters Sept. 23, 1947

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