US2263171A - Gaseous discharge lamp - Google Patents

Description

Nov. 18, 1941. R. F. HAYS, JR; EI'AL GASEOUS DISCHARGE LAMP Filed July 5,- 1940 INVENTOR 1?. F. #0 Y5, m. 19. L E/E'Nfi/V AW WL ATTORNEY Patented Nov. 18, 1941 GASEOUS DISCHARGE LAMP Robert F. Hays, Jr., Bloomfield, and Alva. L. Herman, Montclair, N. J assignors to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a corporation of Pennsylvania Application July 5, 1940, Serial No. 344,014

8 Claims.

The present invention relates to gaseous electric discharge lampsand more particularly to lamps of this type which require no external auxiliary starting equipment.

Lamps of the mercury vapor type are now well known in the art. but have heretofore been limited in their use because of the necessity for auxiliary starting equipment. This is due to.the fact'that a transient voltage higher than that of the source of supply has heretofore been necessary to initiate a discharge, and the current must be limited during operation of the lamp. To this end it has been suggested to employ a series resistance in the for of an incandescent filament surrounding the lamp, but enclosed with the latter in a surrounding container so as to augment the visible light from the discharge.

' Although such construction has decreased the starting voltage of the lamp, nevertheless such lamps have not heretofore been operable without auxiliary equipment, at the usual domestic voltage of 115 to 130 volts, so they can be inserted in sockets within homes. Moreover, when a filament is used as a ballast resistance and designed so as to become incandescent during the starting period, it is not heated sufliciently during the operating period to become incandescent; and when designed to become incandescent during the latter period, it is overloaded during the starting period when the discharge voltage is low.

It is accordingly an object of the present invention to provide a highly eificient light source comprising a gaseous electric discharge lamp and.

an incandescent filament which is operable from wherein no starting electrode is required to first form a glow discharge in order to initiate an arc discharge between the electrodes.

Another object of the present invention is the provision of a gaseous electric discharge lamp utilizing a filament as a series impedance and as a heater for maintaining an operating condition of the lamp, and wherein no auxiliary starting equipment externally of the lamp itself, is required to initiate a discharge.

A further object of the present invention is the provision of a gaseous electric discharge lamp which is operable from the usual source of domestic potential, and wherein no starting electrode isrequired to first form a glow discharge in order to initiate an arc discharge between the electrodes.

Still further objects of the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Fig. ,l'is an elevational view of a lamp con- :tructed in accordance with the present inven ion;

Fig. 2 is a cross-sectional view taken on the line IIII of Fig. 1, and looking in the direction indicated by the arrows;

Fig. 3 is a cross-sectional view taken on the line IIIIII of Fig. 1, and looking in the direction indicated by the arrows;

Fig. 4 is a cross-sectional view taken on the line IV--IV of Fig. 1 looking in the direction in dicated by the arrows, and

Fig. 5 is a cross-sectional view taken on the line V--V of Fig. 1,1ooking in the direction of the arrows, and showing schematically the electrical circuit arrangement within the lamp itself.

Referring now to the drawing in detail, the

lamp shown in Fig. 1 comprises an enclosing conthe usual press portion 8 is sealed to the container, as is common in the incandescent lamp art. A pair of leading-in conductors 9 and ll) of suitable metal, such as magno, nickel, or the like, and provided with a seal-forming portion having 'a coefficient of expansion approximating that of the vitreous container, are sealed to the press and connected to the center contact and shell of the base 6. Prior to aflixing the base to the container, the latter is exhausted through an exhaust stem I I andfilled with an inert gas, such as nitrogen, to prevent arcing. As will be noted, the leading-in conductors are of rod-like form and widen out immediately above the press portionand extend in parallel relation longitudinally of the enclosing container 4.

A pair of bridges l2 and I3 of a suitable material, which may be of metal or an insulating material, tie the leading-in rods together for the purpose of forming a rigid mount for a discharge lamp I4. This lamp, as shown, is of the high pressure mercury type and comprises an envelope l5 of vitreous material capable of withstanding the 'high temperature of operation, such as quartz or the like, and provided with a pair of electrodes II and I1 between which a discharge occurs, as hereinafter more fully described. After evacuation of the envelope I! through an exhaust tip l8, it is filled with an ionizable medium, such as mercury together with an inert gas such as argon, neon. or the like, at a predetermined pressure, to facilitate starting.

The electrode I6, as can be more readily seen in Fig. 5, is preferably in the form of a tungsten helix surrounding a bar of metal having high electron-emissive properties, such as thorium, which emits a copious flow of electrons when heated, as more fully shown and described in the copending application of Daniel S. Gustin and George A. Freeman, Ser. No. 215,578, filed June 24, 1938, and assigned to the same assignee as the present invention. The electrode I1 is similar to the electrode I6 except that it is provided with a filament l3 thus constituting an auxiliary starting electrode which may be provided with a thermionic emissive coating, such as an oxide of barium, strontium, etc., if desired, although this is not essential and in our preferred embodiment an uncoated filament is employed. One end of this starting electrode I9 is connected to the electrode I1 and the other end is connected to a leading-in conductor 20, so that the filament can be heated to an electron-emitting temperature, as hereinafter more fully explained.

The lamp I4 is provided with the customary elongated tapering seal at each end to which the leading-in wire for each electrode and the wire for the filament H! are sealed. This elongated end passes through heat shields 2| and openings 22 (Fig. 5) provided in the bridges l2 and I3, which thus suspends the lamp l4 between the latter in firm engagement therewith. Each bridge is in turn provided with eyelets 23 secured thereto which are of insulating material if the bridges are metal, or of metal if the bridges are formed of insulating material, and which are secured in any suitable manner to the rod-like leading-in conductors 9 and I0.

As can best be seen from Fig. 4, the electrode I1 is connected to the leading-in conductor 9 by a flexible conductor 24, and the electrode I6 is connected by a flexible conductor 25 to one end of a. refractory metal filament 26 secured to a pair of supports 21 and 28 extending upwardly from the bridge l2 and by the end of the leadingin conductor III, as can be readily seen from Fig. 2. A rod-like conductor 29 is sealed into the press 8 and extends upwardly through the bridges l2 and I3 with its upper extremity bent substantially normal to its major axis and provided with l a terminal 30 at its end. Secured to the leadingwhich is provided with a terminal 33 normally engaging the terminal 30, and a rigid guide rod 34 is secured to the conductor [0 and parallels the bimetallic strip to limit deflection thereof upon heating, and which at the same time places a strain on the bimetallicstrip, assuring its return to the normal circuit closing position.

The bridge I3 is also provided with four spaced depending supports 35, 36, 31, and 38 which project completely through the bridge. As can be seen from Fig. 3, the support 36 is'connected by a bar or the like 39 to the conductor 29, and in a similar manner the supports and 31 are electrically tied together by a similar rod 40. -Beneath the bridge l3 a filament is supported, which for the conservation of space is divided, so that a portion 42 is suspended between the supports aaearn 36 and 36, the remaining portion 43 being suspended between the supports 3'! and 38. As shown more clearly in Fig. 4, a flexible conductor 44 connects the support 38 and accordingly one end of the filament 43, to the leading-in conductor 20 (Fig. 5) and through the latter to the filamentary electrode la.

The various parts of the lamp as above described accordingly form a circuit shown schematically in Fig. 5. By reference now more particularly to this latter figure, it will be observed that upon insertion of the lamp in a socket carrying the usual domestic potential of 115 to 130 volts, full line voltage 'will' thus be impressed between the electrodes 16 and H; but since there isan open circuit across the lamp l4, no current flows through the filament 26. At the same time, current from the source flows through a parallel 'circuit including the bimetallic strip 32, the filament formed by the portions 42 and 43, and the lamp filament or starting electrode I9 back to the other side of the source. will thus become incandescent and the starting electrode l9 will be heated to an electron-emitting temperature.

The lamp I4 is designed so that the maximum arc length, commensurate with gas pressure and the starting voltage of 115-130 volts, is obtained. In other words, the arc length or electrode spacing and gas pressure is the optimum for a starting voltage of 115 to 130 volts; and in the lamps we have constructed, it has been found that an electrode spacing of approximately 25 mm. and a pressure of the filling gas of approximately 25 mm. of mercury, operates very satisfactorily with the pressure of the mercury vapor during operation reaching approximately one atmosphere. On the other hand, if the gas pressure is too low, sputtering. of the filament l 9 and blackening of the envelope I5 results; and if the pressure is too high, the discharge will not be initiated at the available voltage of 115-130 volts.

Also, the amount of mercury in the lamp is critical to operation at the voltage of the domestic source, since the mercury pressure and the ballast filament 26 control the arc voltage during operation. For example, the value of the ballast filament 26 is such that it takes only a portion of the line voltage, allowing sufiicient voltage to sustain a stable are at the pressure of the mercury vapor; and if the latter is too high, the arc voltage will take too great a portion of the line voltage, thus making the are unstable and resulting in its extinguishment.

The starting electrode I9 is designed so as to support the arc discharge only during the starting period and atthe same time enable it to be heated to an electron-emitting temperature sufflcient to cause a copious flow of electrons. Moreover, this starting electrode is so shaped as to require a minimum space around the base of the adjacent main electrode I! so that a maximum amount of mercury will be vaporized during operation of the lamp, which thus minimizes fluctuations in the arc voltage and insures a more stable arc despite any line voltage fluctuations.

Upon heating of the starting filamentary electrode l9, as. above mentioned, a discharge occurs between this heated electrode l9 and the electrode I 6 since full line voltage is impressed between the electrodes l6 and I1 due to the filamerits 42-43 limiting the voltage of the parallel circuit including the starting electrode l9. 'Inasmuch as the heated filamentary electrode I 9 The filament 42-43 momentarily functions as cathode, current is accordingly passed through the lamp in only one direction. This "direct current" operation makes the current abnormally high with the resuit that the electrode 48, functioning. momentarily as anode, is quickly heated to an electronemitting temperature by the discharge, after which the heated filamentary electrode l9 and the electrode l8 alternately operate as anode and cathode, as is customary on alternating current.

By this time, the fiow of current through the bimetallic strip 32 heats the same, causing it to deflect against the stop bar 34, thereby interrupting the heating circuit for the starting filamentary electrode I9 and extinguishing the incandescent filament 42-43. However, since the electrode I 6 is now heated to an electron-emitting temperature and full line voltage exists between it and the electrode l I, the electrode I6 will momentarily function as cathode and the electrode H as anode. The lamp thus rectifies the alternating current, and during the forward half cycle the current is again abnormally high which rapidly heats the electrode I! to an electron-emitting temperature, after which the electrodes l6 and I1 alternately function as anode and cathode at normal current fiow.

Although in starting the lamp I 4 it goes through the above described cycle of operation, nevertheless'the total time required, from initiation oi the discharge until it operates at normal currentfiow, is only approximately of three seconds duration. During continued normal operation of the lamp, the incandescent ballasting filament 26 not onlylimits the discharge current and augments the visible light generated by the ensuing discharge, but also heats the bimetallic strip 32 so as to maintain the heating circuit for the starting electrode l9 and the filament 42-43 interrupted. It is also significant to note that the starting electrode l9 receives no por-.

tion 01' the discharge during normal operation since it is entirely carried by the electrode l'l, thus preventing sputtering of the electron-emissive coating if provided on the starting electrode l9. In addition, a heat insulating shield 50 may be employed to prevent undue heating of the seal-forming portion of the container.

It thus becomes obvious to those skilled in the art that a gaseous electric discharge lamp is herein provided which does not require a starting electrode to cause a glow discharge for initiating an arc discharge between the'main electrodes. Moreover, an arc discharge is formed upon connection of the lamp to a source of electrical energy of the'customary domestic poten-' 'tial of 115 to 130 volts without the necessity of cumbersome and expensive auxiliary equipment. By confining all elements necessary to start and operate the tube within the tube itself and employing some of these elements for the production of visible light as well as other functions, which thus augments the light generated by the discharge, a highly efiloient lamp is produced.

Although one embodiment of the present invention has been herein shown and described, it is to be understood that still further modifications thereof may be made without departing from the spirit and scope .of the appended claims.

We claim: 1. An electric lamp comprising a sealed container, a gaseous discharge lamp mounted in said container provided with a pair of main electrodes and an auxiliary electrode adapted to be heated to an electron-emitting temperature from a source of supply of domestic voltage, a filament connected in series with said main electrodes and said source of supplyto serve as a ballast resistance and to augment the visible light generated by said lamp during operation, and a second filament and a heat-responsive element connected in series with said auxiliary electrode and in parallel with said main electrodes and said. first mentioned filament, to cause full line voltage to be impressed across said main electrodes and for causing heating of said auxiliary electrode to an electron-emitting temperature from said source to initiate a discharge between said auxiliary electrode and the oppositely disposed main electrode, and said heat-responsive element being operable to cause disconnection of said second mentioned filament and said auxiliary electrode from the domestic source of supply upon initiation of the discharge in said lamp.

2. An electric lamp comprising a sealed container, a gaseous electric discharge lamp mounted in said container provided with a pair of oppositely disposed non-activated electrodes and an activated filamentary electrode adapted to be heated to an electron-emitting temperature from a source of supply of domestic voltage, a filament connected in series with said non-activated electrodes and said source of supply to serve as a ballast resistance and to augment the visible light generated by said lamp during operation, a second filament and a heat-responsive element connected in series with said activated filamentary electrode and in parallel with said nonactivated electrodes and said first mentioned filament, to cause full line voltage to be impressed across said non-activated electrodes and for causing heating of said activated electrode to an electron-emitting temperature from said source to initiate an arc discharge between said activated electrode and the oppositely disposed non-activated electrode, said heat-responsive element being operable to cause disconnection of said second mentioned filament and said activated electrode from said domestic source of supply with attendant transfer of the are discharge to both of said non-activated electrodes, and said first mentioned filament being operable to heat said heat-responsive element duringoperation of said lamp to maintain said element in an opened position.

3. An electric lamp operable from a source of electrical energy of the customary domestic po tentials comprising a sealed container, a gaseous electric discharge lamp mounted in said container provided with an envelope having an ionizable medium therein at a predetermined pressure, a pair of oppositely disposed main electrodes in said envelope having a spacing therebetween so proportioned to the pressure of the ionizable medium as to sustain an arc discharge between said main electrodes at the voltage available from said domestic source, an auxiliary electrode disposed adjacent one of said main electrodes adapted to be heated to an electron-emitting temperature from said domestic source and of sufiicient area to support an arc discharge with the oppositely disposed main electrode, heat- -responsive means in said container for connecting said auxiliary electrode to said domestic source, and a filament in said container for limiting the current supplied to said lamp during operation and to augment the visible light generated by the latter, said heat-responsive means being operable upon the initiation of said discharge to cause disconnection of said auxiliary electrode from said source with transfer of said arc discharge to said main electrodes, and said filament being further operable to heat said heatresponsive means during continuance of the discharge to maintain said means in circuit-interrupting position.

4. An electric lamp operable from a source of electrical energy of the customary domestic potentials comprising a sealed container, a gaseous electric discharge lamp mounted in said container provided with an envelope containing an ionizable medium at a predetermined pressure, a pair of oppositely disposed main electrodes in said envelope having a spacing therebetween so proportioned to the pressure of' the ionizable medium as to sustain an arc discharge between said electrodes at the voltage available from said domestic source, an auxiliary electrode disposed adjacent one of said main electrodes adapted to be heated to an electron-emitting temperature from said domestic source and of suificient area to support an arc discharge between it and the ppositely disposed main electrode, a filament mounted in said container and connected in series with said main electrodes and said source of supply to serve as a ballast resistance and to augment the visible light generated by said discharge lamp during operation, and a second filament and a heat-responsive element mounted in said container and connected in series with said auxiliary electrode and in parallel with said main electrodes and first mentioned filament, to cause full voltage from said source to be impressed across said main electrodes and for heating said auxiliary electrode to an electron-emitting temperature to initiate said are discharge, said heatresponsive element being operable upon the flow of current therethrough to cause disconnection of said second mentioned filament and said auxiliary electrode from the domestic source of supply with attendant transfer of the discharge to both said main electrodes, and said first mentioned filament being further operable to heat said heat-responsive element during operation of said lamp to maintain said element in a circuitinterrupting position.

5. An electric lamp operable from a source of electrical energy of the customary domestic potentials comprising a sealed container, a gaseous electric discharge lamp mounted in said container provided with an envelope having an ionizable medium therein at a predetermined pressure, a pair of oppositely disposed main electrodes in said envelope having a spacing therebetween so proportioned to the pressure of the ionizable medium as to sustain an arc discharge between said main electrodes at the voltage available from said domestic source, an auxiliary electrode disposed in said envelope adjacent one of said main electrodes adapted to be heated by said domestic source to an electron-emitting temperature, said auxiliary electrode being shaped to confine the space required for both main and auxiliary electrodes to a minimum to prevent the formation 01' cool pockets where condensation of the ionizable medium would otherwise occur and being of an area suflicient to initiate a discharge when heated to an electron emissivity between it and the oppositely disposed main electrode, heatresponsive means normally connecting said auxiliary electrode to said domestic source and operable upon the flow of current therethrough to disconnect said auxiliary electrode from said source with attendant transfer of said are discharge to both said main electrodes, and a filament in said container for limiting the discharge current supplied to said lamp and to augment the visible light generated by the discharge and operable to heat said heat-responsive means during operation of said lamp to prevent return of said means to its normal position.

6. An electric discharge lamp operable from a source of electrical energy of the customary do-- mestic potentials comprising a sealed container, leading-in and supporting conductors extending into said envelope, a pair of bridges supported by said conductors, a gaseous electric discharge lamp suspended between said bridges and provided with a pair of oppositely disposed main electrodes and an auxiliary electrode adjacent one of said main electrodes and adapted to be heated to an electron-emitting temperature from said domestic source, a filament supported by one of said bridges and connected between one of said conductors and one of the main electrodes to limit the discharge current during operation of said lamp and to augment the visible light generated by the discharge, a second filament supported by the other of said bridges and connected to the auxiliary electrode and to another of said conductors to cause full line voltage from said domestic source to be impressed between said main electrodes, a. bimetallic strip normally interconnecting the conductors to which the respective filaments are connected to cause said auxiliary electrode to be heated to an electronemitting temperature and initiate an are discharge between it and the oppositely disposed main electrode and operable upon the flow of current therethrough to interrupt the connection between the conductors to which the respective filaments are connected whereby .the arc discharge is transferred to both said main electrodes, and said first mentioned filament being further operable to heat said bimetallic strip during operation of said lamp to prevent its return to its normally closed position.

'7. An electric lamp comprising a sealed container, a gaseous discharge lamp mounted in said container provided with a pair of main electrodes and an auxiliary electrode adapted to be heated to an electron-emitting temperature from a source of domestic voltage, an impedance device connected in series with said main electrodes and said source of supply to serve as a ballast resistance during operation of said lamp, and a heat responsive element connected in series with said auxiliary electrode and in parallel with said main electrodes and said impedance device, to cause full line voltage to be impressed across said main electrodes and for causing heating of said auxiliary electrode to an electron-emitting temperature from said source to initiate a discharge between said auxiliary electrode and the oppositely disposed main electrode, and said heatresponsive element being operable to cause disconnection of said auxiliary electrode from the domestic source of supply upon initiation of the discharge in said lamp.

8. An electric lamp comprising a sealed container, a gaseous discharge lamp mounted in said container provided with a pair of main electrodes and an auxiliary electrode adapted to be heated to an electron-emitting temperature from a source of supply of domestic voltage, an impedance device connected in series with said main electrodes and said source of supply to serve as a ballast resistance during operation of said lamp, and a second impedance device and a heat-responsive element connected in series .with said auxiliary electrode and in parallel with said main electrodes and said first mentioned impedance device, to cause full line voltage to be impressed across said main electrodes and for causing heating of said auxiliary electrode to an electronernitting temperature from said source to initiate

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