US2191507A - Discharge device - Google Patents

Description

F eb.27,1940. H,J, PANNER 2,191,507

DISCHARGE DEVICE Filed Aug. 14, 1937 INVENTOR I A/ /v I PAN/V5 2% I I ATTO YS Patented Feb. 27, 1940 PATENT OFFICE 2,191,507 DISCHARGE DEVICE Hans J. Spanner, Berlin-Kladow, Germany Application August 14, 1937, Serial No. 159,042 In Germany February 16, 1933 4 Claims.

This invention relates to gaseous electrical discharge devices'and especially to those in which discharge occurs through-a vapor at a pressure sufllciently above that existing at atmospheric 5 temperatures so that-the characteristics of the discharge are substantially varied by evaporation within the device.

This application is a continuation in part of my prior copending application Serial No. 107,190,' filed October 23, 1936.

In my prior application Serial No. 558,148, filed August 19, 1931, and in a prior application of Edmund Germer, Serial No. 500,346, filed December 5, 1930, there are described high temperature metal vapor lamps, both of the type in which the amount of metal is limited to that which is wholly evaporated during normal operation of the lamp and of the type in which an excess of mercury is provided. Both of these 20 types of lamps have been found to operate with great advantage under proper conditions and have gone into wide and commercial use. It is found, however, that both types have certain disadvantages which become apparent if certain 86 undesirable conditions are encountered. Thus, in the lamps with limited dosage if the design of the envelope is such that some small parts thereof during operation are at relatively low temperature, it is found that there may occur a more I) or less appreciable condensation of the mercury thereon and to the extent that this occurs the condensed metal is withdrawn from the vapor atmosphere and the operating characteristics of the discharge are therebylchanged.

' II This disadvantage is overcome by having an excess of the metal present as in the second type v of lamp mentioned above. In that case, however, it is essential that the excess be protected against overheating in order that the lamp may a continue in stable operation and if, .ior example, the lamp should be moved or turned so that the excess metal drops onto a more'highly heated portion of the envelope wall or onto the hot electrode, there may occur such a sudden evap- 45 oration of the excess metal as to seriously change the characteristics of the operating discharge or even to completely extinguish the discharge.

It is accordingly an object of the present invention to avoid these disadvantages and to pro- 50 vide a lamp or other vapor discharge device adapted to operate stably under all conditions and with a uniformly regulated discharge.

This and other objects I attain according to my invention by confining the excess in a narrow tube where it is held securely away from the discharge path and from other more highly. heated parts of the discharge tube and advantageously a sufliciently narrow tube-so that the mercury is held therein by surface tension, e. g., a. capillarypeifect, even though the tube may be 5 moved or turned. Further advantage may be obtained according to my invention by associating with this tubular appendage an electrical resistance heater serving as a ballast for the discharge or otherwise made responsive to the 10 potential drop of the discharge so that when a change of vapor density occurs with its resultant change in the potential drop of the discharge a corresponding increase or decrease in the electrical heater associated with the tubular appendage occurs, with the result that the temperature of the mercury in the appendage is increased or decreased until a correction of the vapor density in the discharge path is achieved. In this way the lamp is made automatically regulating. I

Other means for regulating the heating of the material in the appendage may be used instead of the resistance heater shown, and the heater means may be controlled in other ways from the density of the filling directly or indirectly by other factors which vary with the density, e. g., current loading, electrode temperature, etc., as well as voltage gradient in the discharge path.

I have found it most convenient to use as a 3 tubular appendage for holding the excess mercury the pumping tip through which the envelope is exhausted in the process of its manufacture. This, however, is not essential and an additional tube or tubes may be provided, or, if the lamp is designed with a capillary space between the leadin wire and the wall of the envelope this space may be utilized for the purposes of my present invention; In this latter arrangement the condensed mercury helps to protect the seal against 0 over-heating and against minute leakage; while the lead-in wire, by heat transmitted from the electrodes and/or heat generated therein by resistance, serves the function of the heater to control .evaporation of excessmercury.

In the accompanying drawing and in thisspecification I, have shownand described several preferred embodiments of my invention and certain modifications thereof. These are not intended to be exhaustive or limiting of the invention but are chosenior purposes of illustration in order that others skilled in the art may fully .understand the principles of the invention and theirapplication in practical use and that they may have no difliculty in applying the inven- ,1,

, heat conserving jacket I4, e. g., by means of a tion in numerous other forms, according to the requirements of various conditions and special problems.

In the drawing:

Fig. 1 is a view partly in section and partly in elevation of a typical high pressure mercury vapor lamp embodying my invention; and

Fig. 2 is a view in longitudinal section with cir cuit connections shown diagrammatically of a quartz burner designed particularly for ultraviolet purposes.

Referring first to Fig. 1, I have shown there the significant portion of a lamp for general illumination purposes. of high pressure mercury vapor lamps, which are now in common commercial use, of an inner sealed envelope I0, e. g., of refractory glass, having at each end thereof solid, activated, selfheating electrodes II mounted on lead-in wires I2 which are sealed to and through the wall of the tube by means of an extended sealing tip I3. The envelope I0 is mounted within a protective and supporting frame work I5 of nickel or other refractory metal.

The lead-in wire I2 at the lower end of the tube is connected to one of the contacts of an ordinary connector base and the corresponding lead-in wire of the upper end of the tube is connected through the frame I5 to the other contact of the connector base.

As these lamps are customarily manufactured there is provided beside the seal I3 in the process of manufacture a pumping tip I6 through which the desired filling gases are inserted before the lamp is completed. Ordinarily thispumping tip has been sealed. off as close as possible to the wall of the envelope so as to provide a smoothly rounded end and to prevent condensation in the pumping tip. According to the present invention a contrary practice is provided and this pumping tip is sealed all at a substantial distance from the other walls of the envelope so as to leave an appendage I6 as shown in Fig. l.

This appendage as shown, is of narrow diameter so that it contains a relatively large radiating surface in comparison to its volume, and furthermore, so that the mercury condensed therein tends to hold its position within the tube by capillary attraction or surface tension even if the lamp is turned to a position in which mercury would roll from 'a larger tube.

In the example shown in Fig. l, a further departure has been made from the common construction in that the frame I5 is discontinuous, the member II terminating short of the member I8 by which it is connected to the contact of the connector base and the two being connected through the resistance heater I9 on the tube I6. The heater I9, therefore, serves, at least in part, as a ballast resistance and the heat developed therein depends necessarily upon the potential drop within the tube. The details of construction are shown and described more fully in my prior application No. 107,190.

If the lamp is provided with an incandescent filament ballast within the jacket I4 as more fully described and claimed in my copending application Serial No. 107,190, the heater I9 may be connected in parallel therewith either permanently'or by means'of a thermostatic switch so that the heater operates only until such time as the desired vapor pressure and, therefore, the

This consists, as in the case If an additional ballast is connected in the circuit into which the lamp is inserted the heater I9 will, of course, be in series connection with that part of the ballast. In either case, however,

'its attained temperature will be dependent upon the operating voltage consumed by the discharge. The arrangement as shown in the drawing with the heater wire substantially intimately associated with the tube and without excess heat capacity is an advantageous one because it serves to make the temperature of the mercury in the tube more quickly responsive to the heating developed in the heater wire. The heater wire in this case operates not only to evaporate the mercury when it is heated, but also to assist in condensation of the mercury in the tube after the discharge is extinguished, since the relatively high thermal conductivity of the wire and its connection with the cooler parts of the frame I5 serve to conduct away the excess heat resulting from condensation of the mercury vapor.

In Fig, 2 is shown a similar arrangement. In this case, however, the discharge device is designed primarily as a quartz burner for ultraviolet purposes and is intended to be used in horizontal position as shown in the drawing. For this reason the capillary tubular appendage Ilia is attached to one side; instead of to one end of the envelope Illa. In this case also the heater I9 is shown partly in series and partly in parallel with the resistance ballast 20.

In the operation of either device the applica tion of the voltage when the tube is started first produces a low pressure arc discharge at low potential and the potential may be further decreased by the initial evaporation of the metal vapor. At this stage the ballast resistance consumes a relatively large proportion of the total voltage drawn from the supply line, and accordingly the heater I9 is supplied with increased voltage and current. As the evaporation of the metal vapors proceeds beyond a certain point the potential drop of the discharge begins to increase and as this increase continues the current loading of the discharge decreases and the proportionate voltage consumed by the ballast also decreases with the consequence that the heater I9 is less and less strongly heated until a condition of equilibrium is reached at which no further depletion by evaporation of the metal in the appendage occurs.

When the lamp is extinguished a reverse condition exists in that the heater wire serves to conduct the heat away from the appendage and thus to hasten the condensation of metal vapor therein. This not only serves to restore the excess of mercury to the appendage, but also serves to decrease the restarting period or delay which is required for condensation of, the metal vapors before the discharge can be restarted upon the available voltage.

It will be appreciated from what has been said above that the examples shown in the drawing are particularly adapted for high pressure operation; .that is.to say, operation at a vapor pressure well above the point at which increased vapor density results in increased potential drop of the discharge. The use of such an appendage, however, is not necessarily limited to high pressure devices and even in devices where an increase in pressure produces a substantial decrease in voltage this expedient may be used to produce stability. In such cases, however, the

heater connections would, of course, be changed 7 to be responsive to an increase in the potential drop of the discharge instead 01' to a decrease.

The use of the appendage and heater is important even in. lamps designed for total evaporation of the vaporizable filling inasmuch as the appendage collects the vaporizable material when the lamp is extinguished and, by hastening the condensation, hastens the restarting period of the lamp, and, when the lamp is started, its heater causes rapid vaporization and reduces the time required for heating-up before the lamp attains fullintensity.

What I claim is:

1. A vapor discharge device which comprises an envelope, solid activated electrodes spaced apart therein, a provision of a vaporizable material adapted to be vaporized in operation to provide an atmosphere for carrying the discharge but normally to leave an unvaporized excess, at least one hollow appendage on said envelope spaced from the path of the discharge between the electrodes positioned so that the excess vaporizable material collects therein by condensation, having a total capacity not less than the volume of excess vaporizable material which remains unvaporized during normal operation, and so narrow that said material may be held therein against gravity by surface tension, whereby any part of said vaporizable material which is not normally vaporized during operation of the device is retained in said narrow appendage.

2. The combination of a vapor discharge device as defined in claim 1, a heater in heat-exchange relation with the appendage on the burner, and means responsive to the degree of vapor density of the vaporizable material within the burner for regulating the heating by said heater. I

3. A vapor discharge device which comprises an envelope, solid electrodes spaced apart therein, at least one of which is activated, and a vaporizable material in the envelope adapted to supply during operation a vapor which is excited by the discharge but in amount in excess of that which is normally evaporated by the operation of the discharge, said envelope having at least one recess at a part of the envelope thermally remote from the discharge path so that the vaporizable material collects therein by distillation from hotter parts of the envelope when the discharge is operating and said recess being sufliciently narrow that the vaporizable material which is condensed therein during operation will be held therein against gravity by surface tension.

4. The combination as defined in claim 3 which includes means for heating the vaporizable material in said appendage variably in response to variation of vapor density in the discharge path.

' HANS J. SPAN'NER.

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