US1976149A - Lamp - Google Patents

Description

Patented Oct. 9, 1934 LAMP George Sperti, Covington, Ky., assigner to Sperti Lamp Corporation, New York, N. Y., a corporation of Delaware Application January 25, 1932, Serial No. 588,748

8 Claims.

This invention relates to lamps of the type combining a source of visible radiation and an arc constituting a source of ultra-violet radiation and to an electrode for use particularly in such a 6 lamp but adapted for use in any electric arc lamp.

, In the prior application of George Sperti, Serial No. 572,394, led October 31, 1931, there is disclosed a lamp embodying an outer bulb containing an incandescent lament which provides a 10 source of visible radiation and an inner bulb wherein an arc is established between suitable electrodes in an atmosphere of ionized gas or vapor. The resultant spectrum of such a lamp is that of the incandescent filament having superimposed thereon the spectrum from the arc, the latter providing preferably a substantial amount of energy in the ultra-violet regiorr of the spectrum. By separately enclosing the incandescent filament and the arc, the two sources may be operated substantially independently as regards conditions such as vapor or gas pressure and the arc is prevented from striking to the filament so that it is possible to operate the lamp successfully` at normal house lighting voltages and currents. For such purposes, the lamp and particularly the arc element therein is entirely self-contained and requires no external starting or controlling devices.

As described in the aforesaid application, the arc is established between a pair of spaced electrodes and in order to render the arc self-starting, the electrodes are heated by suitable filaments and the gas or Vapor in the arc chamber is ionized to start the operation of the arc. In order to assist in this ionization, the electrodes preferably embody one or more oxides of material such as thorium, strontium, barium and the like which on being heated have substantial electronic emission. Since one of the necessary attributes of a lamp of this type is long life, the electrodes must be so constituted that they do not evaporate or disintegrate at operating temperatures regardless of age. Moreover, the electrodes should be of a material which does not disintegrate and deposit on the 45 walls of the bulb so as to cause blackening. Moreover, the electrodes should be such that the oxides referred to above are not subjected to unnecessary disintegration during ordinary operation of the lamp but are used only for starting purposes.

One of the objects of the present invention is to provide a novel form of electrode for use in lamps of the above type or in any electric arc lamp whereby the electrode is substantially non-vaporizable during operation and hence can be used -these electrodes are heated by means of laments for long periods and is not harmed by prolonged operation.

Another object is to provide an electrode having an arcing surface of an oxide such as zirconium oxide on which the arc is maintained duringnormal operation and also embodying oxides such as strontium and barium which are effective in starting the arc but are substantially not affected during normal operation of the arc.

Only one embodiment of the invention has been illustrated in the accompanying drawing, but it is to' be expressly understood that said drawing is for purposes ,of illustration only and is not to be construed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawing,

Fig. 1 is a perspective view of a lamp embodying the invention; and

Fig. 2 is a sectional view of a part of the lamp 75 shown in Fig. 1.

As shown in Figs. 1 and 2, the lamp embodies a bulb 1 :of any suitable size and Shape and the usual orany suitable base 2. Where the lamp is intended to emit ultra-violet light, the bulb 1 80 should be of material which transmits ultra-violet radiations of the desired wave lengths, which ordinarily will include only wave lengths longer than about 2800 to 2900 Angstrom units. Sealed in the neck of the bulb is a standard 3 whereby the usual conductors 4 and 5 are introduced into the bulb and whereby the various elements are supported within the bulb. An incandescent lament 6 is supported by means of wires 7 and 8 from the stem 3, the Wire 7^constituting aconnection between one end of said filament and the conductor 4. Said filament is further supported by one or more wires 9 which are carried by a bead 10 formed on the upper end of an inner bulb 11 which is also supported on the stem 3 by suitable means such as a supporting band l2 and supports 13 and 14.

Within the bulb 1l are electrodes 15 and 16 which are described more fully hereinafter, and

17 and 18. The lament 17 is connected at one end with the filament 6 by means of a wire 19 and at the other end to the lament 18 by means of a wire 20 and resistance 21. The filament 18 is connected by a wire 22 with the support 13, the latter being connected to the conductor 5j When current is supplied to the lamp, it ilows in series through the filament 6, filament 17, resistance 2l, and filament 18. The filament 6 heats up to incandescence and provides a source of visible radiation while the filaments l'l-and 18 heat the electrodes 15 and I16. The potential drop through filaments 17 and 18 and resistance 21 is impressed across the electrodes in any suitable manner, so that the arc is established in the inner bulb 11. It will be understood that the construction thus far described constitutes no part per se of the present invention but is shown merely to illustrate one practical form of lamp to which the invention may be applied.

As shown more clearly in Fig. 2, the electrodes 15 and 16 each have the form of a tube bent into a U and they are so supported in the inner bulb l1 that the bights of the tubes are adjacent. These electrodes are formed of materials which are substantially non-vaporizabie at operating temperatures, and they may be of second-class conductor material, that is, of material which has high resistance and is substantially a nonconductor when cold but which has low 'resistance and becomes a good conductor on heating. An example of such non-vaporizable second-class material is zirconium oxide. which is preferably molded into the bent tube form shown in the drawing to constitute thev electrodes.

It will be understood however that the electrodes may also be formed of metal such as tungsten and the like or of any other material which is non-vaporizabie at operating temperatures, said material being suitably formed into the U-shaped tubes shown in the drawing. The filaments 17 and 18 extend through the tubes and are thus protected from the arc. These tubes may be supported in any suitable manner, and as shown. the ends of each tube are provided with supporting bands 23 to which are secured supports 24 that are fused in the walls of the inner bulb 11. As clearly shown in Fig. 2. one of the supports 24 of each tube serves as a means for connecting the heating filament 17 with the filament 6in one instance and the heating filament 18 with the support 13 in the other instance, and due to this fact. the voltage drop through the heating filaments is applied across the electrodes to establish and maintain the arc.

To assist in starting the arc. the electrodes are provided as above stated with oxides having electronic emission. Preferably these oxides are located adjacent the ends of the tubes and remoto from the bights thereof. In this way as the tubes are heated. the electronic emission of such oxides is effective to assist in ionization of the gas or vapor in the inner bulb and thus to assist in starting the arc. As soon as the arc strikes. however, it establishes and maintains itself on the adjacent bights of the tubes which constitute arcing surfaces. At the same time, the resistance of the arc path is decreased. most of the current flows through the arc, and the heating filaments 17 and 18 cool off. The oxides at the ends of the tubes are thus no longer subject to the full heating of the filaments 17 and i8 and are not affected by the arc itself. the outside of the tubes, as indicated diagrammaticaliy at 25, or they may be incorporated with the zirconium oxide during the manufacture of the electrode. The filaments 1'7 and 18 are insulated fi'om the electrodes in any suitable manner as by coating them with an insulating cement.

zirconium oxide is particularly suited for use in such electrodes because it does not melt or vaporize until temperatures much higher than normal operating temperatures of the lamp are The oxides may be coated on4 reached. Thus not only do these electrodes have 'long life, but they do not evaporate and cause deposits to form on -the walls of the bulb. Substantially no disintegration of such an electrode can be observed after long periods of operation.

The inner bulb l1 should be of material which transmits the desired ultra-violet radiations produced by the arc. Where mercury or other vapor is employed in the inner bulb which produces radiations shorter than those desired. the inner bulb 11 may be of any suitable material which absorbs and does not transmit the undesired short waves, or the inner` bulb may be provided with a filter 36 of mica or the like which does not transmit the undesired radiations.

While only one embodiment of the invention has been described and illustrated in the drawing, it is to be expressly understood that the invention is not limited thereto but is capable of considerable variation. Moreover, the use of the novel electrode is not restricted to the particular type of lamp shown in the drawing, but may be employed in any electric arc lamp either with or without the incandescent filament 6. Furthermore. many of the advantages of the invention can be obtained with the heating filaments outside the electrodes, which in such case need not be hollow; and similarly as respects many features of the invention the electrodes need not be of second-class conductor material but may be of any substantially non-vaporizable material. Therefore reference is to be had to the appended claims for a. definition of the limits of the invention.

What is claimed is:

1. An electric arc lamp comprising apair of U-shaped electrodes disposed with their bight portions adjacent, said bight portions comprising arcing surfaces of material substantially nonvaporizabie during arc operation and the legs of said electrodes including an oxide having high electronic emission 'when heated, means for supplying potential to said electrodes, and means for heating said electrodes to start the are.

2. An electric arc lamp comprising a pair of hollow U-shaped electrodes disposed with their 'bight portions adjacent, said bight portions oomprising arcing surfaces of material substantially non-vaporizable during arc operation and the legs of said electrodes including an oxide having high electronic emission when heated. heating filaments within said hollow electrodes, and means for energizing said filaments and electrodes.

3. An electric arc lamp comprising a pair of U-shaped electrodes disposed withtheir bight portions adjacent. said bight portions comprising arcing surfaces of material substantially nonvaporizable during arc operation and the legs of said electrodes including an oxide having high electronic emission when heated, means for energizing said electrodes. and electrode heating means connected in parallel with said electrodes.

4. An electric arc lamp comprising a pair of hollow U-shaped electrodes disposed with their bight portions adjacent. said bight portions comprising arcing surfaces of material substantially non-vaporizable during arc operation and the legs of said electrodes including an oxide havin;r high electronic emission when heated. means for energizing said electrodes, and heating filaments within said electrodes, said heating filaments being connected in series with one another and in parallel with said electrodes.

5. An electric arc lamp comprising a pair of hollow U-shaped electrodes disposed with their bight portions adjacentsaid bight portions comprising arcing surfaces of zirconium oxide and the legs of said electrodes including one or more oxides having high electronic emission when heated, means for supplying potential to said electrodes, and heating filaments Within said electrodes, said filaments being connected in series with each other and in parallel with said electrodes.

6. An electrode of the class described comprising a U-shaped member of second class conductor material, the bight portion of said member comprising an arcing surface which is substantially non-vaporizable during arc operation, the legs o said member including an oxide having an arcing surface and the legs of said element having 'incorporated therein an oxide having high electronic emission when heated.

GEORGE SPERTI.

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