US2166951A - Discharge device - Google Patents

Description

July 25, 1939. E. GERMER DISCHARGE DEVICE Filed Jan. 25, 1936 INVENTOR Patented `luly 25, 1939 UNITED STATES DISCHARGE DEVICE Edmundl'Germer, Berlin, Germany, assigner of eighty-seven and one-half per cent to Ulrich W. Deering and Hans Joachim Spanner, both of Berlin, Germany Application January 25, 1936, Slil N- 60,774

In Germany July 1, 1929 i Claims.

This invention relates to gaseous electrical discharge devices and more particularly to such devices in which a metal vapor constitutes at least a part of the gaseous atmosphere through 5 which the discharge occurs. A

The present application is a continuation in part of my prior applications: Serial No. 500,346, filed December 5, 1930, and Serial Nos. 397,428 and 397,429, filed October 4, 1929. In these applications I have described and claimed devices in which a discharge occurs between fixed electrodes through an atmosphere of a gas or vapor. The electrodes as described in my prior application are specially activated with the result that l5 there is only a very small electrodel drop and consequently the electrode operates at relatively low temperatures except for the actual arcing point, and the ends of the tube behind the electrode are therefore the coolest part oi the tube at which condensation is most likely to occur. l

Furthermore, as set forth in my prior application, the electrodes in such a tube are advantageously made of nickel, but even at the relatively low temperatures of operation nickel tends to evaporate very slowly from the electrode to the wall of the enclosing envelope, where the nickel deposit produces a darkening and a consequent loss of luminous efficiency of the tube.

According to the invention which forms the subject of the present application, condensation of vapors on the ends of the enclosing'envelope and darkening of the principal luminous portion ofthe envelope are avoided by so constructing and/or mounting the envelope that currents in the gas or vapor are set up within the electrode chambers near the path of the discharge from the electrode. These currents at once tend to sweep any evaporated or sputtered electrode material away from the luminous portion of the tube and back into the electrode chambers where it will condense on the cooler parts of the tube; and, in the case of vapor discharges, serve by heating of these cooler parts of the tube to prevent excessive condensation of the vapor filling.

In the drawing I have shown:

In Figure l a partial longitudinal sectional View of preferred embodiment of my invention;

In Figure 2 a longitudinal sectional view of another embodiment of my invention;

In Figure 3 a fragmentary sectional view of a tube having the lower part of its electrode chamber insulated;

In Figure 4 a view in elevation of a therapeutic ultra-violet radiator embodying my invention;

and

In Figure 5 a. view on an enlarged scale partially in longitudinal section and partially in elevation of a gas discharge device such as that used in Figure 4. i

In Figure l, I have shown a lamp designed for standard installation and replacement for general illumination purposes. The gas discharge device proper is mounted Within a protective jacket I0 on a standard connector base II. Activated, self-heating, cold-emissive electrodes I2 are mounted on lead-in wires I3 at each end of the envelope I4 and the envelope is filled with a fixed gas at low pressure to start the discharge and a vaporizable material, which when vaporized becomes the principal agent of the luminous discharge.

The electrodes I2 are conductive bodies of refractory metal such as Ni, W, Ta, Pt,etc.and associated therewith a mass of at least partially reduced oxide of an emissive metal such as BaO with or without other more refractory oxides.

The filling gas is preferably one of the rare inert gases, and the vaporizable material, a metal e. g., Hg, Ti, Ga, alkali metals, etc.

This lamp is described more in detail in the copending application of Hans J. Spanner, Serial No. 744,206. filed September 15, 1934.

The lamp of Figure 1 is burned in vertical position and generally baseup, thus giving in the upper end the special convection action hereinafter described. U

When the lamp is thus operated in vertical position, the constrictions I5 in the wall of the envelope have a special function closely related to that of the vertical positioning already mentioned, namely to break up the space within the envelope into more or less separate convection zones. These constrictions turn the convection currents which pass down along the cooler Walls inwardly toward the hot Zone of the discharge where, becoming heated and entrained in upward currents, the gases or vapors are again turned upward. Only the coolest part of the gases, from which all electrode material will have been deposited on the electrode chamber or the constriction, will escape from the upper chamber into the principal luminous portion of the tube below. These cyclic currents over the electrodes tend to carry any material which is vaporized or sputtered from the electrodes directly to the Wall of the electrode chamber, and there to 'deposit it on the relatively cool surfaces where it does not interfere with the major luminous radiation from the tube. Y

At the bottom of this lamp the action is less I5 produces a downward convection current toward the electrode end. Without the constriction these currents pass smoothly along the wall to the bottom of the envelope where they are caught-in the upward draught due to the heating oi the electrode and the discharge path, and then pass rapidly up into the center of the tube eventually to return to the vicinity of the wall and the downward convection current. At this return there will always be some tendency to deposit sputtered or evaporated electrode material. The constriction l5, however, intercepts this smooth ilow of convection current and turns the downward current from the wall of the tube Il inwardly toward the intensely heated arc path. Thus the cooler convection current from the wall of the tube tends to impingeupon the intensely hot current in the arc path just above the electrode with the consequence that they are suddenly expanded, thus creating a lateral blast toward the Walls of the electrode chamber and further opposing the smooth downward ilow of the cool convection current. As a consequence of this action more of the sputtered and evaporated electrode material will be deposited in the electrode end of the tube and left in the principal luminous portion between the constriction l5.

As will be evident to those skilled in the art, from what has already been said, these lamps are adapted for operation on either direct or alternating current, but with direct current it is preferable to operate the lamp with the cathode end uppermost.

In Figure 2, I have shown a modiiled embodiment of my invention in whichl both ends oi.' the tube are positioned upwardly from the luminous portion of the tube so as to take fullest advantage ci the action speciilcally described above in connection with the upper electrode chamber and constriction.

The construction and form of the electrodes l2a, the electrode mountings I6, the lead-in wires I3a, and the seals II-IB, and the wall strip I9, as well as the particular ingredients and proportions of the filling gases and vapors have been fully disclosed in my said prior application Serial No. 500,346 and need not be discussed in detail herein. It is suihcient to say that the tube ida, its electrodes I2a, and other parts, are similar in principle and operation to the tube and electrodes etc. of Figure 1. They are constructed for high temperature operation and the electrodes I2a are activated electrodes.

The iilling of the lamp includes a vaporizable metal, e. g., mercury, thallium, gallium, alkali metals, etc.

'I'he wall of the envelope at the mouth of the electrode chambers is constricted as shown at a so that it projects inwardly close to the path or the arc or other discharge between the electrcdes, and consequently the wall will become most highly heated at this constriction. In consequence any gases which ilow down along the cooler wall of the electrode chamber will be deiected into a hot zone at this point, will be strongly heated and expanded and will be blown thereby back into the electrode chamber, as more fully described in connection with Figure 1.

The effect of the constriction is twofold; Firstly, it serves mechanically to deilect the gases toward the hotter central zone, and secondly, it serves by its own higher temperature to heat and therefore to expand the gases, and thus to blow them inwardly and back to the electrode chamber. y

Although this action will occur most readily with the pole vessels in the upright position as shown in Figures 2 and 3, since. in this position the natural gravity currents resulting from the diil'erencein density of' the heated and cool gases and vapors will coincide with the currents due to their expansion and contraction respectively at the hot and cool temperatures, nevertheless, a similar action will occur to some extent regardless of the position of the electrode ends.

In some cases and especially with smaller lamps, e. g., -up to 1.5 amps., current input, it is advisable to cover the lower parts of the electrode chambers with heat insulating materials such as asbestos, thus accentuating the effect of heating the gases at the mouth of the electrode chamber.

Figure 3.

In the example shown in Figure 2 this circulation within the electrode chambers is further iacilitated by provision of special cylinders surrounding the electrodes and spaced from the Walls of the electrode chamber. These in ei'- iect are stacks heated at the bottom by the discharge, which create an up-draft, while the cooler walls oi' the electrode chambers tend to contract the hot gases issuing from the top of these stad-rs" and thereby to produce a downdraft along these walls. This vstrong convection circulation results first in sweeping all sputtered electrode materials to the end of the tube behind the electrode and secondly in maintaining a, constant heating of the walls of the electrode chamber which prevents objectionable condensation thereon.

In the example of Figures 4 andA 5 that part 0l' the tube for the arc path does not enlarge again beyond the constrictions |522. 'I'his part of the tube being relatively small and close to the arc will all be highly heated and obviously its upper end at the constriction |5b will be at the highest temperature. In this case, therefore, as in the case illustrated in Figures 1 and 2, the constrictions l5b serve both mechanically and thermally to deilect the gases from their smooth down-iiow along the tube wall. y

Although I have shown in the accompanying drawing and described above one specific embodiment of my invention it should be understood, of course, that my invention is not limited to this particular form or construction and if the principles set forth above are born in mind those skilled in the art will have little diiliculty in designing other forms and constructions by which the desired blast or convection current may be produced.

What I claim is: f

.1. An electrical discharge device of the type which comprises a container having electrode chambers and a principal luminous portion between the electrode chambers, electrodes at least one of which is a fixed solid electrode spaced from the walls of its electrode chamber, and a lling in said container adapted to carry the discharge comprising a vapor condensable at ordinary room temperatures, which device is characterized by means adapted to deilect away from the container wall gases which tend to pass from the electrode chamber into the principal luminous part of the container and to turn them back toward the electrode chamber and thus to confine mainly within the electrode chamber the This is illustratedI for example, in

convection currents which pass over the electrode.

-2. An electrical discharge device as defined in claim 1 in which the deiiecting means is approximately beneath the solid electrode whereby the upward convection currents therefrom pass over the electrode and tend to sweep upward away from the principal luminous portion of the con-I tainer any materials which are given oil.' from the electrode.

3. An electrical device as defined in claim 1 in which the deflecting means comprises a constriction in the wall of the container adjacent the mouth of the electrode chamber.

4. An electrical discharge device as defined in claim 1 in which the deiiecting means comprises thermal insulation about the container adjacent the mouth of the electrode chamber adapted to maintain during normal operation a higher wall temperature near said mouth than at adjacent parts of the container wall.

5. In a vapor arc lamp the combination of ixed electrodes at least one of which is an activated arc electrode, an envelope enclosing an elongated space around and between said electrodes. and an arc carrying illling, comprising a material which is vaporized by heat from the discharge, and .said envelope having pole vessels surrounding said electrodes, but suiciently spaced therefrom Vso that their temperatures.will be lower than the condensation temperature of any material vaporized from the electrode by the heat of the arc, whereby to concentrate in the pole vessels away from the principal luminous portion of the enlvelope any darkening from such vaporized matelrial, and in which the pole vessel is a separate member carried by, but spaced over a major part of its area from the inner surface of the envelope whereby the wall of the pole vessel is insulated from the open atmosphere so as to be maintained at a temperature above that of the wall of the envelope around said pole vessel and any condensation of the metal vapor must occur on said envelope wall in preference to the wall of the pole vessel.

EDMUND GERMER.

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