US2187860A

US2187860A - Lead-in conductor for mercury vapor tubes

Info

Publication number: US2187860A
Application number: US109177A
Authority: US
Inventors: Lauster Franz
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-11-04
Filing date: 1936-11-04
Publication date: 1940-01-23
Anticipated expiration: 1957-01-23

Description

7 F. LAUST ER LEAD-IN CONDUCTOR FOR MERCURY VAPOR TUBES Jan. 23, 1940.

Filed Nov. 4, 1936 Patented Jan. 23, 1940 UNITED STATES PATENT OFFICE LEAD-IN CONDUCTOR FOR MERCURY VAPOR TUBES In high pressure mercury vapor tubes, as is known, the output of radiation increases as the specific load of the discharge is increased. An object of this invention is to provide a lead-in s conductor for tubes adapted to carry high current loads.

This high current load necessitates that all dead spaces which might act as condensation points for the mercury vapor be avoided. The

to familiar tungsten wire leads, which are fused into quartz by using a single transition glass, avoid dead spaces but can only carry a low current load and are therefore unsuitable. In the present invention metal foils of less than 0.02 mm. thick- 16 ness are used as current leads. Such toils can be fused directly into the quartz tube and can carry current loads up to ten amperes. Thus a high order or radiation output is obtained with tubes made according to this invention and a satisfac- U tory operating life is achieved atthe same time owing to the comparatively low vapor pressure developed.

with high pressure mercury vapor tubes there is a danger that part of the mercury required for 85 operation may condense in the pole chambers, where the temperature is considerably lower than in the remainder of the tube. To prevent such condensation, the wall thickness of the pole chambers is made greater than that of the reso mainder of the tube, thereby increasing the temperature on the inner walls of the pole chambers. As a further precaution the section of the tube available to the arc may be constricted in the viclnity oiLthe pole chambers.

' In some cases the enlargement of the wall thickness may be limited by the external or the internal diameter of the pole chambers. In this event, the pole chambers may be screened oi! from the remainder of the tube by means of flanges which will cause more electrical energ to be converted into heat in the pole chambers. The provision of constrictions and/or flanges as such is known. but these have hitherto been employed for different reasons. It is only when tubes. ac-

cording to the invention. develop vapor pressures in excess or live atmospheres that a constriction in the vicinity of the pole chambers will produce any considerable increase in the potential gra-" dients with the accompanying conversion into 50 heat within the pole chambers.

In the accompanying drawing, Fig. 1 is asomewhat diagrammatic longitudinal sectional view of showing the lead-in foil. Fig. 3 is a perspective view of part of a lead-in foil and part 01 an electrode connected therewith. Fig. 4 is a perspective view similar to Fig. 3 of a modified embodiment of the leadein foil and electrode. The 5 tube I consists of quartz. The are tube portion 2 is screened off from the

pole chambers

5 and 6 by means of flanges 3 and 4. The thermionic electrodes 1 and 8 can, for example, consist oi. tungsten wire wound round a thicker timgsten wire, or other metals with high melting points may be used to advantage in some circumstances. Substances having a low work function, e. g. alkaline earth oxides, are applied to the electrodes inknown manner, the electrodes preferably being heated to the necessary incandescence by the discharge itself. On the thick tun sten wires arefastened metal toils 9 and I which are fused into quartz capillaries of suitable section to form a high vacuum-tight seal. In doing this, it is advanta eous to lay the ends of the tungsten wires in a fold oi the toil so as to obtain a good electrical contact with the drawing in of the quartz. The i'nils are protected against the discharge it. as shown in the illustration. the ends of the pole chambers have an opening only exacti.v sumcient for the passage or the tungsten wires. The metallic lead in foils are made of a refractory metal such as tungsten or molybdenum and. or a width of about 3 to mm., are of a thickness which is less than 0.02 mm. and preferably less than 0.01 mm. Such thin foils can be fused directly into the quartz. They form a completely vacuum tight seal, requiring no further sealing means. The outer current leads may not be connected directly to these foils since the latter are not or great mechanical strength and, moreover. are often damaged where they are not embedded in quartz. by oxidation during operation. It is. therefore. necessary to attach a strong wire to 40 these foils and to connect the external current leads thereto. As shown on the drawing, this is done by folding the foils over once and placing the wire between the foils. The foils may be penetra ed at the folds so that the connector wire is positioned axially, as shown by the drawing. Current connection to the electrodes is accomplished in similar manner. The connection between the tails andthewiremaybeeflectedby welding. if desired. In general, however, welding is not necessary. The fusing of the foils into the quartz must be carried out in vacuum. It is. therefore, convenient to place the foils and the folded-in connector wires in a quartz tube having a suitable inside diameter and to evacuate the interior thereof. Alter softening of the quartz, the quartz tube is completely pressed together by meansoiexternalairpressuresothatitislndirect contact throughout with the foil, includinz the folded parts. Upon cooling of the quartz, the rigid material encom the toil prevents the connection from becoming loose. This joint is thus adequate even for large currents. To avoid condensation of the mercury, the wall I! of the pole chambers 5 and i is made thicker than the wall II o! the arc tube .2. Owing to the greater fall of temperature within the walls or the pole chambers, even the smaller transformation of electrical energy around the incandescent elsetrodes will produce sufllcient heating on the inner walls of the pole chambers. The eflect of this improvement is further enhanced by the screening flanges 1 and 4. As a. result of these two measures, condensation of themercury inside the pole chambers is prevented. The internal diameter of the arc tube 2 is made as large as possible to ensure that the arc is kept away from the walls of the arc tube, limited however to a certain extent as otherwise the arc becomes unstable in operation. It is also important to fix the dimensions of the arc tube so that the coldest spot therein is maintained at such a temperature so as to produce a vapor pressure in excess otfive atmospheres. For instance 1118!! Pressure mercury vapor tubes, according to the illustration have proved satisfactory with an internal diameter of 8 mm., a wall thickness or 1.5 mm. and a distance between electrodes of 40 mm., operating with a voltage drop of about 26 volts/cm. and a current load of 1.0 ampere. The wattage is about 100 watt.

In some cases it is advantageous to use electrodes heated by external means. In this event, a further fusion lead is required and this can be provided by using two thin metal ioils of about equal thickness, one as the lead-in for the current and the other for the heating of the electrode.

What I claim is:

A lead-in conductor for conducting currents of up to 10 amperes to high pressure mercury vapor tubes made of quartz and having solid end portions comprising a strip metal foil having its ends folded back and wires connected to said foil by passing between the layers of the folded baclrends of the foil, the foil including at least a portion of the folds embedded in quartz.

FRANZ LAUS'I'ER.

CERTIFICATE OF CORRECTION Patent No. 2,1 7, 60. January 25, 19mg.

- 'Fmnz IAUSTER.

It is herebylcertified that'error appears ip'the above m mbered patent requiring cprrection as follows In' the heading tpthqprihtfed specification,

' after line 5,- insert; in Germany Novemper' 15, 1935"; and that the and Letters Patent should be read, with this correction therein that the aam e may confom to the reord 0! F116. ca'se' in the fatal 1t .Offibe.

Signed. and sealed thia'lhth day- 0'! may, A. D. 1911.0.

--Henry Vain Ara dfile, (Seal) Acting Gomhiaaioner o; Ptents.

' after line 5, insert In Germany Novemper' 15, .1935",

CERTIFICATE OF CORRECTION:

' J m 2;. 19m;- rmuz IAUS'I'ER. 7 It is herebylcertified thaterror appears ipthe abovo n'fimb requiring cprrection as foliowa In the heading tp-thqprihtfed specification, and that the sa id Patent No. 2,187,860.

ered patent .Letters Patent should be read with tibia-correction therein that the 5am? may. confoim to the rebord of tgh'e case in the Paterit .Offi'ce."

Signed and sealed thia'lhth 1 0'! May, A. n. 191p.

Agting Gmm'niaasloneg' qr Ptexits.