US1374647A - Arc incandescent electric lamp - Google Patents

Description

E. A. GIMINGHAM.

ARC INCANDESCENT ELECTRIC LAMP.

APPLICATION flLED OCT-15, I915.

Patented Apr. 12, 1921.

UNITED STATES PATENT OFFICE.-

EDWARD ALFRED GIMINGHAM, OF LONDON, ENGLAND.

ARC INCANDESCENT ELECTRIC LAMP.

Specification of Letters Patent.

Patented Apr. 12, 1921.

Application filed October 15, 1915. Serial No. 56,016.

cent Electric Lamps, of which the following is a specification.

This invention relates to improvements in arc incandescent lamps, that is to say lamps which have substantially the outward appearance and construction of the ordinary incandescent electric lamp and a bulb which is of such form and is so closed as to allow of its being properly exhausted; while the lamp is furnished with means for forming or maintaining an are within the bulb between two poles of tungsten or other suitable highly refractory material, such means being of simple construction which will allow of the complete exhaustion of all oxygen from the bulb. In hitherto known constructions of lamps with tungsten pole ieces in an inclosed globe the poles have een moved apart or held apart by mecha-- nism within the globe which have made complete exhaustion impossible. The invention relates more particularly to lamps 'of the type specified which after exhaustion are filled with an inert gas such as nitrogen or argon for example. A minute quantity of oxygen may be constantly supplied within the lamp by heating some suitable substance such as barium chlorate byexposing it to the heat ofthe are. This facilitates gthe starting of the are.

' In one constructioirof nitrogen filled lamp passing of the, type referred to two poles of electrodes are fixedf'permariently apart'and the in orhood foi the oles "lS ionipedf by a heater ,,'where=f' .a ar can readily. be formedbetweeng r,

' terminates {in an electr u ent. t r n upon = 'the-;poles=.with j,low tension currents asP-com-t monly 'in use for ordinary lighting. According to the present invention, the heater which serves to ionize the gases also serves to carry one pole of the arc and, on ionization being completed, the arc is formed between an electrode in parallel with one end of the heater and a point on the heater or an electrode in arallel with the other end of the heater. ccording to one form'of this invention the heater is arranged in close proximity to one electrode and it has upon it a shield, of tungsten for example, at a point suitable to form another electrode, so that an arc of the desired size may be formed between the two electrodes. The heater therefore serves first as in ionizer and then at one point as one of the electrodes. In-

stead however of the shield above referred to being actually formed upon the heater, it may be carried upon one of the leading in wlres of the heater so as to be electrically in one piece therewith, and in such proximity thereto that the gas between the electrodes is properly ionized. In either case the current passed through the heater for the purpose of ionizingthe gas and start: ing the arc-is cut off, either automatically or by a hand operated switch, after a few moments, andthe current then passes from one electrode to the other across the arc gap.

The invention as applied to a lamp on a di- In the construction shown in Fig.' 1, three leads A, B, C, are introduced into a globe D,-containing an inert gas. by means of the ordinary-"Edison stem. Outside the globe s'A andBareconnected-together' 1 f lead, and the connectBdthrough t nitable re- I The-lead h gnrhe stem and Oils-E, of tungsten.

the-"tWfe'lead 7 wan-the molybdenum or other suitable highly re- The other lead A, terminates in an expansion strip F, (formed fractory substance.

for example of two metal strips having different co-efi'icients of expansion such as molybdenum and nickel or molybdenum and nickel copper alloy fused together) the head of which F normally'makes contact with a head G on a lead A carried by an extension of the Edison stem. The lower end of the lead A is connected with one end of the heater H, which is looped and at its other incandescent will end joins the lead 0. Around the end of the heater H which is nearest to the elec trode E is arranged a spiral I of stout wire, of tungsten for example, which is secured to I the lead C at the same point as the heater H.

The operation of the lamp is as follows The current passes through the leads A, A and the expansion strip F, tothe heater H and thence to the lead C. Immediately the heater is incandescent the gas between it and the posit-ive pole is ionized and a small current passes between the pole E and the heater. Upon the expansion strip becoming heated by the hot gas rising from the heater it warps and breaks the contact between F and G. This has the effect of allowing the current at the full potential of the external supply to operate in breaking down the resistance of the are gap, and the current forming the arc flows by means of the lead B through the electrode E across the gap to the coil or shield I. The current now passes no longer through the heater H proper. The heater H and the shield I are however practically one, as they are both carried by the end of the lead C, this being one convenient method of mounting the shield instead of directly on the heater H.

In the arrangement of heater and electrodes shown in Fig. 2 the electrode E is a solid sphere of fused tungsten, which when ive practically equal illumination in all directions, and the heater H between the leads A and C- is straight and. has a thickened portion I of tungsten for example to serve as protection and form the negative electrode in the middle.

In the arrangement shown in Fig. 3 the ionizer H is also straight, but here it is surrounded by a coil I as in Fig. 1 serving as a shield andforming the negative electrode. The ositive electrode E is here again of the flat orm shown in Fig. 1.

In Fig. 4 is shown another arrangement, somewhat similar to that of Fig. 2, but having an additional device for insuring that the arc shall burn between the actual thickened or heavy portions forming the electrodes E, I. The positive electrode E in the form of a sphere is carried upon a portion B of the lead B, which is connected with the lead .B

by an expansion strip K. On the are being struck in the manner described in connection with Fig. 1, the expansion strip warmed by the heat conducted from the hot electrode the electrode E and the heater H, instead of between E'and the thickened portion I, owing toithe latter being less hot than the heater of smaller section. I The mdvement of the electrode E toward the negative elecare with it until it is maintained between E and I as desired.

This expansion strip may be set at such an angle with the heater that while the arc is drawn along to. the desired position between E and .I, the length of the arc gap is also increased. Such an arrangement enables the electrode to be placed nearly touching the heater when the lamp is out and facilitates the starting of the are by reason of the short gap to be ionized. By careful construction of the ex ansion strip any desired length of arc ma be formed.

In Fig. .5 is shown a positive electrode in the form of a hollow sphere having a thickened portion which is intended to act as a protection against premature burning through at the point of arcing. This form may be made in two or more parts fused together. The two halves are molded and the edges held together and fused in an electric are for example. By careful construction of the thickened portion the whole surface of the sphere is by conduction brought to approxlmately uniform temperature,

1 The electrode shown in Fig. 6 has fiat surfaces and is triangular in section; such an electrode would when incandescent throw the maximum beam in a direction at right angles to its largest fiat surface, the are striking at the apex of the triangular shaped electrode."

The electrode may also be rectangular in section, as in Fig. 1, in which case the maximum beam will be in a direction at right angles to the face opposite that on which the arc strikes.

In Fig. 7 is shown a lamp similar in construction to that shown in Fig. 1, but furnished with a tube L in position and containing barium chlorate orsimilar chemical which at thetemperature of the lamp when a burning gives off a minute quantity of o xygen. It is found that this device assists the The ogygen attacks.

formation of the arc. the surfaces of the electrodes on cooling. IWhen the lamp is again started the slight film of oxid formed on the electrodes is easily volatilized by the passing of the current. It is this action apparently which assists in breaking down the resistance of the arc gap. Probably the resistance of the around the electrodes is 'lowered,by the dis turbing action of the volatilized particles of oxid, and the arc is thus more easily established. The presence of the oxid 'cannot be detected with the naked .eye, but its presence on the electrodes is established by the momentary wandering of the are when the lam is restarted. The volatilized oxid is not in sufficientquantity to discolor the bulb ofthe lamp, such thin films which may be deposited on the glass being white in color.

In this figure the lead C is shown furnished with a sleeve of silica M. This has been found to be of advantage when there is any tendency for the arc to run up the leads. The lead B may also be so protected if required. In mercury vapor. lamps a quartz sleeve has been used surrounding the lead in wire passing through a body of mercury and carrying the anode, so that the arc may. not run to the mercury.

Instead of the expansion strip break F, F, G described, any other convenient form of break, such as a magnetic break may be employed. The are may if desired be started by means of a hand operated switch outside the lamp.

It is very necessary thatthe lamp should be thoroughly exhausted of all tracesof water vapor, and gases occluded by the elec trodes and leads before the inert gas is admitted.

The heater or ionizer H may consist of tungsten or molybdenum wire, or of tungsten mixed or in combination with refractory earths such as zirconia, thoria, calcium oxid, titanium oxid, tantalum oxid, or other highly refractory substances. Some of these refractory oxids possess the property of ionization to a very high degree when heated. For example, a satisfactory ionizer may be made by mixing zirconia and tungsten in equal parts and forming same into threads or filaments by any of the well known methods.

of obtaining light-giving bodies but in carrying out this invention the object is not to carry the process of reduction too far but, to maintain as far as possible within the filament the ionizing properties of the refractory earths, so that the repeated striking of the arc by means of the ionizer during the life of the lamp may be possible. Filaments such as those mentioned above, in which refractory oxids are present in any quantity, are not efficient light giving bodies, as their surfaces when viewed under the microscope show them to be dull and irregular, but they are active ionizers at a much lower temperature than similar filaments constructed of pure metals such as tungsten or molybdenum.

In the construction of the ionizer from mixtures of tungsten-and refractory earths, the well known method of using a carbon binder may be employed, which can be removed later by the passing of a current in an atmosphere of hydrogen or other reducing gas, or as only short thick filaments are rerequired they maybe formed without the addition of a carbonaceous binder.

The ionizer may be straight or spiral or may be mounted in the form of a loop, having thev protection acting as the negative electrode, common with the negative pole of the ionizer as illustrated in Figs. 1 and 3, or

Similar filaments have been previouslyconstructed with the object it may be straight, having as in Figs. 2 and 4 a protection acting as the negative electrode in the center of the ionizer. The negative electrode may be of hammered or drawn tungsten or an suitable'refractory conductor. In. fact t e same refractory materials may be used for both the ionizer and the protection acting as the negative electrode. The ionizer may be of such dimensions that no protection is required at the point of arcing. It is, however, desirable that the ionizer should be used as far as possible only as a means of starting the arc.

The shield on the heater may also be produced by burning the are at a high current density until a sufficient quantity of sputtered metal has been deposited on the surface of the ionizer. sputtered metal is a triangular needle and offers good protection to the ionizer at the point of arcing, besides assisting in strikingp the arc at a normal current. rect current lamps the major portion of the light of the lamp is obtained, may be constructed of fused tungsten or tungsten alloyed with other refractory metals, or tungsten mixed or in combination with refractory earths such as those specified above for use in the construction of the ionizer or. negative electrodes. By suitably arranging.

the ionizer the positive electrode may be wholly constructed from a fused oxid such as zirconia,which is a non-conductor when cold, but which when heated conducts electricity.

These positive electrodes may be formed in any desired shape, and may be so arranged in the lamp that the maximum illumination is thrown in any desired direction.

A satisfactory arc may be maintained at a pressure of approximately 1} an atmosphere but I wish it to be understood that the arc may be started and maintained at pressures of gas as low as approximately th of an atmosphere or even lower to pressure of 1 atmosphere or higher.

What I claim as my invention is 1. In an electric arc incandescent lamp a bulb containing an inert gas, a heater adapted to ionize the'gas, an electrode in parallel with one end of the heater, and a second Each particle of the electrode surrounding a portion of therent has been passed, the other electrode being'electrically connected with the heater and being, at least in part, interposed between the first electrode and heater.

4. In an electric arc incandescent lamp, a bulb containing an inert gas, a heater adapted to ionize the gas, an electrode in parallel with one end of the heater, and having means adapted to move it relatively to the other electrode upon a current passing, the other electrode being carried by the heater.

5. In an electric arc incandescent lamp, a bulb containing an inert gas, a heater composed oftungsten and a refractory earth in combination adapted to ionize the gas, an

bulb containing an inert gas, a heater adapt- -ed to ionize the gas, an electrode of tungsten in parallel with one end of the heater, and a second electrode of tungsten located, at least in part, between the heater and said first electrode.

EDWARD ALFRED GIMINGHAM.

Witnesses JOHN HENRY RUssoN, WALTER J. sKERTEN

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