US2374304A - Mercury feeding apparatus - Google Patents

Description

April 24, 1945. Q E, QWINGS MERCURY FEEDING APPARATUS Filed Dec. 1, 1943 L/NE lnvervtor .m W W n w n 1 wfim m n H c b LINE 8 electrodes.

?atcnied Apr. 24, 1%5

STATES NT @FEEQE Charles E. Owings, Cleveland, Ohio, assignor to General Electric Company, a corporation of New York Application December 1, 1943, Serial No. 512,-4'l1 13 Claims.

My invention relates in general to the manufacture of electric discharge lamps or devices of the type comprising a sealed envelope containing a predetermined quantity of a vaporizable metal such as mercury. Mor particularly, my invention relates to method and apparatus for introducing a predetermined quantity of vaporizable metal into the envelope of such devices.

In the manufacture of electric discharge lamps ofthe well-known fluorescent type in general use at present, a quantity of mercury is introduced into the lamp envelope during the lamp exhaustlng operation. To insure a properly performing lamp, the quantity of mercury which actually passes into and remains within the lamp envelope must be at or above a certain minimum amount.

In the usual type of exhausting and mercury filling machine employed in the manufacture of such fluorescent lamps, the electrodes of the lamp are heated followirm the mercury filling operation by an electrical current passing through the The mercury is introduced into the envelope by means of an injecting device or dispenser which deposits a measured amount of mercury into a vertical conduit communicating with the interior of the envelope, the mercury dropping through the conduit into the envelope and lodging within the lower end of the latter where it is vaporized by reason of the heated condition of the envelope and electrode at the lower end of the lamp. If the mercury released by the dispenser into the conduit actually passes into the lamp envelope, an arc will eventually strike across the ends of each of the energized lamp electrodes due to the lower resistance of the mercury vapor arc path thereacross. Such a local arc discharge thus causes an end glOW to develop within the lamp envelope. For various reasons, however, such as failure of the mercury dispenser to operate properly or lodging of the mercury elsewhere, a sufficient amount of the mercury released by the dispenser doe not always pass into the lamp envelope with the result that it is frequently necessary for the operator to perform additional manually-controlled mercury injecting operations, as,by hand switches. The determination of'whether or not additional mercury is to be introduced into a lamp by the operation of such manually-controlled injecting means there'- fore requires the constant observance by the operator of either the lamps being processed or of suitable indicator means.

One object of my invention is to provide a] method and apparatus for automatically introducing into the envelope of an electric discharge device a predetermined minimum quantity of a vaporizable metal.

Another object of my invention is to provide a mercury vapor lamp exhaust apparatus having means for automatically effecting the introduction of additional amounts of mercury into the lamp envelope in the event a predetermined minimum amount of mercury is not initially introduced thereinto.

, Still another object of my invention is to provide an indexing type lamp exhaust machine having, in combination, means for automatically feeding a predetermined quantity of mercury to the envelope of a lamp when positioned at one of thestations of said machine together with additional means for automatically fiecting the introduction at a subsequent station of additional amounts of mercury into the lamp envelope in the event that a predetermineed minimum amount of mercury is not then present in the lamp.

A featureof the invention is the provision of means controlled by electrical condition existing within the lamp envelope for effecting .the automatic introduction of the additional mercury into the lamp envelope.

Further objects and advantages of my invention will appear from the following description of a species thereof and from the accompanying drawing in which:

Fig. 1 is a diagrammatic representation of an exhaust machine head with associated control 7 to a lamp exhaust machine of the type described and claimed in United States Patent No. 2,247,513-A. J. Marshaus, issued July 1, 1941,

, and comprising a, carrier or turret l0 having a plurality of heads I I which are mountedat regularly spaced intervals about the periphery of the turret and are advanced in turn through a. similar number of stations by counterclockwise indexing movements of the turret. As shown in Fig. 1, each head It is provided with suitable holders I! for carrying an electric discharge lamp is which may be of the well-known fluoionizing potential of mercury. The envelope l4 is completely sealed except for. the opening through an exhaust tube I'I extending from one end of the envelope. The lamp I3 is held by the holders l2 in a vertical position in the head II with the exhaust tube I'I uppermost and extending into a compression rubber chuck l8 mounted on the lower end of an exhaust head IS. The chuck I8 is provided with a compressible rubber ring 2ll which is mounted within the chuck housing 2| and is compressed tightly around the exhaust tube I! to thereby provide an airtight connection between the exhaust tube and the chuck housing 2|. The rubber ring is compressed by rotation of a cap 22 threaded onto the chuck housing 2|, the said cap pressing a metal guide washer 23 up against the underside of the rubber ring through ballbearings 24 interposed between the cap and washer.

The chuck housing 2| is provided with an exhaust passageway 25 in axial alignment with both the exhaust tube I1 and a vertically extending passageway 26 in the exhaust head l9. Thesaid exhaust passageway 28 is formed, in part, by the opening through a rubber tube 21 disposed longitudin l y within the exhaust head. and is connected to suitable exhausting means, such as a vacuum pump. through a connection pipe or conduit 23 and a rotary valve mechanism (not shown), as described "in the previouslymentioned Marshaus patent. In case there be no lamp in the head II, the operator can. close.

or pinch of! the passageway 23 in the exhaust head I 3 by means of. a pinch clamp comprising a pressure member 29 and an actuating cam or lever 30 for pressing the pressure member 23 against the rubber tube 21 to flatten the same and thus close or pinch of! the passageway a, predetermined-amount d mercury, extends through and has a free but sufflciently close sliding fit in the restricted upper end portion 38 of thedischarge passageway to form an effective mercurytight seal therebetween. The said slide member 36 is vertically reciprocable in the reservoir 33 to first introduce the recessed portion 31 thereof into the mercury pool 34 so as to allow the recess 31 to fill with mercury and to then withdraw the recessed portion down through and beyond the lower end of the restricted portion 38 of the discharge passageway 35 to thereby allow the mercury trapped in the recess to drop out .of said recess and into the exhaust passageway 26. The slide member 35 extends up through the reservoir 33 and is connected at its upper end to a soft iron or steel piston 39 which reciprocates within a bell housing made of non-magnetic material and attached to the upperend of the reservoir in an airtight manner.

During the course of its movement around the machine the lamp I3 is exhausted while it moves a at the said station-A and is energized one or more times, depending upon the amount of mercury .to be introduced into the lamp. The magnetic field produced by the energized coil 4| attracts therethro zh- The pressure member 23 and the cam lever 33 are plvotally mounted on the exv haust head I! within a slot 3l'therein. In the inoperative or open position of the pinchclamp wherein therubbertube 21 is left open, the pinch clamp actuating lever or cam 33 occupies an "out position (as shown in full lines in Fig. 2) wherein it is further removed from the center of rotation of the turret III than it is when in its closed or in" position indicated in dotted lines in Fig. 2. 7

Each exhaust head I! is provided at the top thereof with a separate mercury feeding or injector device 32 for. discharging a measured amount of mercury into the vertical exhaust passageway 23 in the head IS, the mercury then passing down through the said passageway and through the 'exhaust'tube .I'I into the lamp envelope l4. The mercury feeding device 32 may be of any suitable form but preferably is of the electricallyactuated type disclosed and claimed in copending- U. S. patent application Serial No.

504,716, filed October 2, 1943; by E. B. Isaac et al-., and comprises a hermetically sealed reservoir or container 33 which is filled with a quantity of mercury 34 or other vaporizable metal and is mounted on top the exhaust head I! with a discharge passageway 38' at the bottom of the reservoir ,in airtight communication with the exhaust passageway 26 in the exhaust head. A hollow slide or feed member 38, having a small pocket or recess 31 in its outer side for holdlns and raises the piston 33 in the bell housing so as to move the slide member 36 upwardly from its normal lowered position and introduce the pocket 31 thereof into the pool of mercury 34 .in the reservoir 33. After a brief interval of time sufilcient to allow the pocket 31 to fill with mercury from the pool 34, the coil 4| is de-energized to allow the slide member 33 to fall freely of its own weight and carry the mercury in the pocket 3! down through and beyond the restricted portion 33 of the discharge passageway '35- where it drops out of said pocket into the passageway 26 and thence down through the said passageway and exhaust tube l1 into the lamp envelope. The required amount of mercury for each lamp is made up by' one or more actuations of the cuits 42, 42'. The current is supplied to each of the cathodes l5, l5 by'means of a pair of curved plate-shaped track contacts 43, 43 and 43', 43'

against which the lamp lead-in wires l6, l6 wipe during the index of the lamp to station A and while it is positioned at said station. The track contacts ,43 or 43' for each cathode are connected through separate ballasts 44, 44' respecranging from approximately 200 to 250 C. Due. to the-relatively slow rate of evacuation of the.

3 In accordance with the invention, auxiliary mercury feeding means are provided for automatically feeding additional amounts of mercury into the lamp envelope in the event such a mercury deficiency condition exists therein as indicated either by the total absence of a local arc discharge or by the absence of a discharge of predetermined minimum intensity, at one or both envelope, a mercury vapor atmosphere is then created therein, As a result, a mercury vapor arc discharge will shortly strike first across the ends of the lowermost cathode l 5 and then across the uppermost cathode i5 due to the lower resistance of the mercury vapor arc path across each cathode as compared to the resistance of the cathode itself. The resulting drop in resistance in the cathode heating circuits 82, 42' which thus occurs when the local arc discharge strikes across the individual cathodes I5. i5 then causes the current flowing in the said circuits to increase and the incandescent ballast lamps 44, 44 to burn with appreciably greater brightness than theretofore.

Inasmuch as the current intensity of the local arc discharge, and thus the current flow through and therefore the brightness of the ballast lamp 44 or M, increase as the mercury vapor pressure within the envelope increases. the relative brightness of the ballast lamp M or 66' at any given instant is therefore a. direct indication of the mercury vapor pressure existing at that particular instant within the envelope and there fore an indication that mercury is present in the envelope in an amount at least equal to the amount required to establish such a pressure. Thus, when the ballast lam M or M attains at least a predetermined level of brightness. such condition then denotes the presence of at least a predetermined amount of mercury within the lamp envelope.

To insure the production of properly performing lamps, it is necessary that mercury be present in the lamp envelope It in an amount at cathodes I5, l5, the operation of such auxiliary mercury feeding means being governed by suitable control means the operation of which is con-- trolled, in turn, by the presence or absence of a local arc discharge of such predetermined minimum intensity at one or both lamp cathodes. The introduction of the additional amounts of mercury into the lamp envelope l4 may take place at any time after the lapse of a definite period of time during which a local arc discharge of such predetermined minimum intensity would be normally expected to occur at one or both cathodes: I5, l5. Preferably, however, the additional mercury is introduced while the lamp is positioned at the next succeeding station B (Fig. 2) since by that time a local arc discharge of the said predetermined minimum intensity normally should be present at least at the lowermost cathode l5 if the required minimum amount of mercury is present in the lamp envelope.

The auxiliary mercury feeding arrangement according to the invention comprises, in general, means for automatically operating the mercury feeding or injector device 32 on the exhaust head i9 one or more additional times when no local arc discharge, pr a discharge of less than the required minimum intensity, is present at one or both lamp cathodes, In the particular form of the invention illustrated, the auxiliary mercury feeding arrangement comprises a solenoid coil 45, similar to the coil 4! at station A, which is lowered over the bell housing of the mercury injector 32 as soon as the latter is positioned at station B. The lowering and raising of the. coil is effected bythe change in shape of a cam $6 mounted on the main drive shaft 41 of least equal to a predetermined minimum amount.

The mercury feeding device 32 is therefore arranged to feed to the envelope at station A a quantity of mercurt equal to. but preferably somewhat in excess of, the said predetermined minimum amount. If all or a sufficient quantity of the mercury thus released by the feeding device 32 at station A actually enters the lamp envelope so that the said envelope then contains such predetermined minimum amount of mercury. then the mercury vapor created in the lamp envelope by the vaporization of the mercury therein will shortly attain a predetermined minimum pressure value sufficient to support a local arc discharge of predetermined minimum intensity across each of the cathodes l5, I5. For various reasons, however, such as the failure of the mercury feeding device 32 to operate properly or lodging of the mercury elsewhere, the amount of mercury which actually enters the lamp at station A is sometimes less than the said predetermined minimum amount. The failure of the local arc discharge either to form at the cathodes l5, I5 or to reach a predetermined minimum intensity is. therefore an indication that there is either no mercury at all, or less than the required minimum amount of mercury, in the lamp' envelope it.

- the machine and engaging one end of a follower thereby form an energizing circuit 54 for the said coil. The said solenoid circuit 54 is normally maintained in an open-circuit condition by 'an interrupting switch 55. A cam 56, mounted on the main drive shaft 41 and'having one or more lifts or steps 5'! (preferably three, as shown), in-

termittently closes the said switch 55 for brief intervals, while the coil 45 is in its lowered posi tion around the bell housing 40, to thereby intermittently operate the mercury injector 32 so as to feed additional amounts of mercury to the lamp envelope l4.

Connected in the solenoid circuit 54 is a suitable relay device 58 for opening the said circuit when a mercury vapor arc discharge of the aforesaid predetermined minimum intensity exists in the lamp I3 across one of the lamp cathodes I5, l5, preferably the lowermost cathode I5. The said relay 58 may be of any suitable type which is responsive to conditions attending the existenceof such a predetermined intensity are discharge in the lamp to thereby interrupt the solenoid circuit 54. Thus, the relay 58 maybe of the current-sensitive type which is actuated by a predetermined minimum current flowing therethrough, the relay being set, for the irposes of the invention, to operate only when the current flow in the cathode heating circuit 42 or 42' and through'the relay equals or exceeds a predetermined value a determined by the existence of a local arcdischarge of the aforesaid predetermined minimum intensity at the cathode l5 or I5. Preferably, however, the relay 58 is of the photoelectric type which is actuated by an increase in the intensity of the light striking the photoelectric cell or tube of the relay. Such a photoelectric relay may be of the well-known commercial types in use at present and it is preferably actuated by the increased light from one or the other of the ballast lamps 44, 44' in the cathode heating circuits 42, 42', the relay being set to operate only when the light from the ballast lamp 44 or 44' equals or exceeds a predetermined brightness as determined by the existence of a local arc discharge of the aforesaid predetermined minimum intensity at the cathode l5 orv l5. For adjusting the intens ty of the light that operates the photoelectric relay, suitable means I are provided such as electrical variables (for instance a resistance) connected in the circuit of the relay itself. or an adjustable or iris" diaphragm 59 interposed between the exciting ballast lamp 44 or 44' and the photoelectr c element'of the relay 58. If desired, the separate indicator or ballast lamp or lamps may be omitted, and the photoelectric relay operated directly by the brilliance of the end glow in the lamp. In that event, a bright glow of predetermined minimum intensity, due to an arc discharge of the required minimum intensity, indicates ample mercury. and

less brilliance due merely to incandescence of the cathode, indicates a deficiency of mercury.

switch connected in the solenoid circuit 54 and actuated bv the relay coil. The relay armature or switch 52 is normally maintained in a. closed, ircuit position as shown. and is opened only when the photoelectric tube 50 is excited by the ballast lamp 4,4 to thereby energize the relay coil BI and so pull the armature 62 away from the relay switch contact 58.

During substantially the entire indexmovement of the lamp l3 from station A to the auxiliary mercury feeding station B, and also while it is positioned at the said station B, the lamp lead-in wires l6, l5 ride along and en age the track contacts 43, 43' to thereby maintain the cathode heating circu ts 42, 42 closed and therefore the cathodes l5, l5 heated. If at least the required minimum amount of mercury has actually entered the lamp envelope H at the main mercury filling station A, then the substantially continuous heating of the cathodes l5. l5 between stations A and B serves to maintain the mercury in the lamp in a continuously vaporized state to thereby support a mercury vapor arc discharge of the aforesa d predetermined 'minimum intensity' across the lowermost cathode l5 dur ng the index of the lamp -to station B and while it is positioned thereat.

If upon reaching the auxiliary mercury feeding station B a local arc discharge of the said predetermined minimum intensity persists across the lowermost lamp cathode I5, the ballast lamp 44, because of its greatly increased brightness, will excite the photoelectric tube 60 of the relay 58 thus causing the relay switch 62 to open and thus break the solenoid circuit 54 so as to prevent operation of the mercury injector 32 at station B. However, if there be no local arc discharge across thelowermost cathode [5 when the lamp reaches station B, or if a discharge of less than the aforesaid predetermined intensity is present, then the ballast lamp 44, because of its relatively low or insuflicient brightness, fails to excite the, photoelectric tube 50 sufficiently to cause the relay switch 52 to open. As a result, the said switch 62 remains in its normal closed-circuit position so that when the operating switch 55 in the solenoid circuit 54 is subsequently closed by the first step 51 on the cam 56, the solenoid circuit is completed and the mercury injector 32 operated once to feed a definite amount of mercury into the lamp envelope. If, after the introduction of such additional mercury into the lamp envelope, a mercury vapor discharge of the required minimum intensity should develop across the lowermost cathode I5. then the ballast lamp 44 will emit sufficient light to actuate the relay 58 and open the solenoid circuit 54 so as to prevent further operation-of the mercury injector 32. However, if a mercury vapor arc discharge of the required minimum intensity, still fails to occur across the lowermost cathode l5, then the photoelectric relay 5! remains unactuated and the relay switch 62 remains closed. As a result, the injector 32 is operated a second time, upon closure of the switch 55 by the second step 51 on cam 56, to thereby supply a second shot of mercury to the lamp ii. If, after this second shot of mercury, a mercury vapor arc discharge of the required minimum intensity still fails to develop across the lowermost cathode l 5 so that the relay 58 still remains unactuated, then the injector is operated a third time, by the closure of switch 55 by the third step on cam 56, to thereby supply a third shot of mer-- cury to the lamp.

The three additional shots of mercury automatically supplied by the injector 32 at the auxiliary mercury feeding station B should result in the introduction of sufficient mercury into the lamp envelope I4 to cause the formation of a mercury vapor arc discharge of the required predetermined minimum intensity across the lowermost lamp cathode I5 in practically all cases. If such an arc discharge fails to occur after the three additional actuations of the mercury injector device 52 at station B, then such failure is an-indication either that the lamp itself is defective or that the mercury injector device 32 is not operating properly.

To prevent the operation of the auxlliaryimercury injection arrangement at station B in the event there be no lamp present in the head II,

the solenoid circuit 54 is preferably provided with a suitable cutout switch 64 for interrupting the said circuit when such condition exists. The said switch 64 is preferably actuated by the pinch clamp lever 30, the switch normally being in an open-circuit position and being engaged by the pinch clamp operating lever 30 when the latter is in its out position (indicating the presence of a lamp in the head) to thereby close the switch duringthe interval when the head I l is positioned 2,374,304 at station B. The switch 6| may be mounted on an arm 65 extending from the stationary standard 65 through which the solenoid coil support rod l9 extends, the switch being located in a position in the path of the rotary travel of the pinch clamp lever 30, when the latter is in its out position as shown in Fig. 2, so as to be engaged and actuated thereby when in such position. If desired, a suitable indicator lamp 61 may be connected in the solenoid circuit 54 in parallel with the solenoid coil 65 for the purpose of indicating whether or not the auxiliary mercury feeding arrangement is operating to supply additional mercury to the lamp at station B.

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

1. In combination, means for feeding a quantity of vaporizable metal into an envelope, means for vaporizing the vaporizable metal introduced into the envelope, means including an electrical circuit for establishing an arc discharge through the metal vapor, means controlled by said electrical circuit for detecting the existence of a discharge of predetermined minimumintensity', and means controlled by the detecting means for operating the said feed means to feed an addi tional amount of the vaporizable metal into the envelope upon nonexistence of such a minimum intensity discharge.

2. In combination, means for feeding a quantity of vaporizable metal into an envelope, means for vaporizing the vaporizable metal introduced into the envelope, means including an electrical circuit for establishing an arc discharge through the metal vapor, said electrical circuit including an electric lamp connected therein to provide an indication of the existence of an arc discharge of predetermined minimum intensity, and means controlled by the light output of said lamp for operating the said feed means to feed an additional amount of the vaporizable metal into the envelope upon non-existence of such a minimum intensity discharge. 4

3. In combination, means for feeding a quantity of vaporizable nietalinto an envelope, actuating means for the feed means, means for vaporizing the vaporizable metal introduced into the envelope, means including an electrical circuit for establishing an arc discharge through the metal vapor, said electrical circuit including an electric lamp connected therein to provide an in-- dication of the existence of an arc discharge of predetermined minimum intensity, and photoelectric relay means responsive to the light output of said lamp for controlling the operation of said actuating means to cause the feeding of an additional amount of the vaporizable metal into the envelope by the said feed means upon nonexistence of such a minimum intensity discharge.

4. In combination, electrically actuated means for feeding a quantity of vaporizable metal into an envelope, means including an electrical actuating circuit for operating the feed means, means for vaporizing the vaporizable metal introduced into the envelope, means including an electrical circuit for establishing an arc discharge through the metal vapor, and means controlled by the said last-named arc establishing circuit for controlling the operation of said actuating circuit to predetermined minimum intensity.

5. In combination, means for feeding a quantity of vaporizable metal into an envelope, means for vaporizing the vaporizable metal introduced into the envelope and for establishing an arc discharge through the metal vapor, said last-named means comprising an electrical heating element in the envelope and an electrical circuit for said heating element, and means controlled by the nonexistence of a discharge of predetermined minimum intensity for operating the said feed means to feed an additional amount of the vaporizable metal into the envelope.

6. In combination, means for feeding a quantity of vaporizable metal into an envelope, means for vaporizing the vaporizable metal introduced into the envelope and for establishing an are discharge through the metal vapor, said last-named means comprising an electrical heating element in the envelope and an electrical circuit for said heating element, and means controlled by said electrical circuit for operating the said feed means I means comprising an electrical heating element in the envelope and an electrical circuit for said element including an electric lamp connected to provide an indication of the presence of a discharge of predetermined minimum intensity, and

means controlled by the light output of said lamp for operating the said feed means to feed an additional amount of the vaporizable metal into the envelope upon nonexistence of such a minimum intensity discharge.

8. In combination, electromagnetically actuated feedmeans for feeding a quantity of vaporizable metal into an envelope, an electrical actuating circuit including a solenoid for operating said feed means, means for vaporizing the vaporizable metal introduced into the envelope, means including an electrical circuit for establishing an arc discharge through the metal vapor, andmeans controlled by the said last-named arc-establishing circuit for controlling-the operation of the solenoid actuating circuit to cause the feeding of an additional amount of the vaporizable metal into the envelope by the said feed means upon nonexistence of a discharge of predetermined minimum intensity.

9. In combination, electromagnetically actuated feed means for feeding a quantity of vaporizable metal into an envelope, an electrical ac.- tuating circuit including a solenoid for operating said feed means, means for vaporizing the vaporizable metal introduced into the envelope and for establishing an arc discharge through the metal vapor, said last-named means-comprising an electrical heating element in the envelope and an electrical heating circuit for said element, and means controlled by said heating circuit for controlling the operation of the solenoid circuit to cause the feeding of an additional amount oi the vaporizable metal into the envelope by the said feed means upon nonexistence of a discharge predetermined minimum intensity.

10. In combination, electrically actuated al paratus for automatically feeding mercury into the envelope of an electrical device containin a resistance heating element, means for effecting a repeat operation of the feeding apparatus when its initial operation fails to introduce sufllcient mercury into the enevelope comprising an electrical circuit including an electric lamp connected in series with said heating element to a current source so that said heating element is heated to establish thereacross an arcdischarge through the mercury vapor whereby said lamp is lighted to a lower lever of brilliance when current is passing through the heating element and to a higher predetermined level when an arc is established, and light-sensitive relay means responsive to the light emitted by said lamp and connected to efl'ect a repeat operation of the feeding apparatus only upon failure of the lamp to be lighted to the higher predetermined level of brilliance.

11. An indexing type lamp exhaust apparatus comprising, in combination, a carrier member having a lamp-supporting head mounted thereon and indexed thereby to a plurality of worl: stations. mercury feed means on said head for feeding mercury into a lamp mounted in the head, actuating means at one of said stations for operating said feed means to thereby feed a quantity of mercury to the lamp, means at a subsequent station for determining the presence or absence of a predetermined minimum amount of mercury in the lamp, and means controlled by said last-named means for operating the said feed means at said subsequent station to feed an additional amount of mercury to the lamp when less than the said minimum amount of mercury is present therein.

12. An indexing type lamp exhaust apparatus comprising, in combination, a carrier member having a lamp-supporting head mounted thereon and indexed thereby to a plurality 01' work stations, electrically actuated mercury feed means on said head for ieeding mercury into a lamp mounted in the head, electrical actuating means for operating said feed means at one of said stations to thereby feed a quantity of mercury to the lamp, means for vaporizing the tion.

vaporizable metal introduced into the envelope, means including an electrical circuit for establishing an arc discharge through the mercury vapor in the lamp at a subsequent station, auxiliary actuating means for operating said feed means at the said subsequent station, and means controlled by the arc-establishing circuit for controlling the operation 01 said auxiliary actuating cury feeding device on said head for feeding mercury into a lamp mounted in the head, electromagnetic actuating means for operating said feeding device at one of said stations to thereby feed a quantity of mercury to the lamp, means for vaporizing the vapcrizable metal introduced into the envelope, means including a cathode in the lamp and an electrical heating circuit for said cathode for establishing an arc discharge through the mercury vapor in the lamp at a subsequent station, auxiliary electromagnetic actuating means including an electrical actuating circuit for operating said feed means at the said subsequent station, and a relay connected in said actuating circuit and controlled by the said heating circuit for-controlling the operation of said auxiliary actuating means to cause the feedmg of an additional amount of mercury to the lamp .by the said feed means upon'nonexistence of an arc discharge of predetermined minimum intensity in the lamp at the said subsequent sta- CHARLES E. OWINGS.

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