US2178326A - Method of and means for eliminating occluded gases from an enclosure - Google Patents

Description

m1. 31,1939. J. LECORGUILLIER 2 8.32 METHOD OF AND MEANS FOR ELIMINATING OCCLUDED GASES FROM AN ENCLOSURE Filed Dec. 50, 1936 zzyz Patented Oct. 31, 1939 UNITED STATES METHOD OF AND MEAN FOR ELIMINATING QCCLUDED GASES FRQM AN ENCLOSURE .lean Leccrguillier, Suresnes, France, assignor to Socit Anonyme pour les Applications dc lElectricit et des Gaz Bares, Etablissements Claude-Paz & Silva, Paris (Seine) France, a

corporation of France Application December 30, 1936, Serial No. 118,358 In Great Britain February 15, 1936 i Claims.

The present invention relates to a method of and means for eliminating occluded gases from an enclosure, for example a tube intended for electric discharges, inter alia for the clean-up of discharge tubes having an atmosphere of vapour under high pressure.

In the method at present employed for cleaning-up or degassing of tubes havinga discharge in an atmosphere of mercury and provided at each end with an electrodecoated with emissive oxides, a certain quantity of mercury (Figure l) is placed beforehand in the tube A or (Figure 2) in a pocket B provided in the exhaust tube C connecting the discharge tube to the vacuum 5 pump. To free the discharge tube and the electrodes of their occluded gases, the said tube is caused to operate, if necessary after the introduction of one or more rare gases, while maintaining the vacuum under an electrical load greater than normal. At the same time the pocket B is heated and if necessary the tube by an external source of heat. In practice, however, diificulties are encountered due to the hot mercury vapour carried off into the exhaust tube, resulting more particularly in drops of mercury descending into the tube which may lead to the fissuration of cracking of its glass.

This disadvantage may be partly remedied, as shown'in Figure 3, by disposing the exhaust tube C at the base of the discharge tube on the fixed branch of a mercury filling device D having a rubber tube and funnel. By raising the said device D, a certain quantity of mercury is introduced into the tube A. The tube is operated under an electrical overload. The mercury distils and its vapour redescends into the branch D where it condenses, thus obviating any obstruction of the exhaust tube C. When all the mercury introduced into A has been almost entirely distilled, the mercury is re-introduced into A by manipulating D, and so forth. These operations, however, necessitate rather lengthy manipulations and moreover, in the case of the production of high-pressure atmospheres, it is not possible to maintain a sufficiently high tension of mercury Vapour, which is detrimental to the subsequent good behaviour of the electrodes.

The present invention remedies all the abovementioned disadvantages. It comprises, for eliminating the occluded gases from an enclosure by the application of. heat and a vacuum, efiecting, externally of the said enclosure, the heating of a liquid furnishing a readily condensable vapour such as mercury, in order to cause the latter to circulate in the enclosure in question, then condensing the said vapour after its circulation in the enclosure and returning the condensed liquid into the heating vessel.

Figure 4 shows diagrammatically and by way of example an apparatus for carrying out the method according to the present invention. The discharge tube A which has to be degassed is provided at each end with an exhaust tube C and C respectively. The lower exhaust tube C is connected to the mercury vaporising vessel V, which is, if necessary, lagged or heated externally, and the exhaust tube C is connected by a tube E to the vessel V in which it is immersed in the liquid for forming a liquid seal. On the course of the tube E, it is surrounded by a cooling jacket (condenser) R and is provided in the part below R with a tube G connected to the vacuum pump.

The apparatus operates as follows: The liquid in V and if necessary the exhaust tube C and the tube A are heated, a vacuum being produced at the same time. The mercury vapour evolved by the liquid in V ascends through C into the tube A, passes through the latter and leaves through the tube C, to return through the tube E into the vessel V in the form of liquid which is condensed during the passage of the said vapour through the portion E which is surrounded by the condenser R. It will be seen that this part of the apparatus constitutes a vacuum pump acting by diffusion and carrying away the gases liberated by the discharge tube until they reach the outlet of the condenser R where they are pumped away through G. During the operation, a discharge is passed through the tube A and, if desired, one or more rare gases may be introduced and evacuated. The pressure in the tube A during the operation depends chiefly upon the rate of vaporization and the cross-section of the exhaust tube C.

' If, at the commencement of the formation ofthe discharge tube, a little oxide of mercury is formed on its walls, it is merely necessary to heat the latter in order to decompose the oxide,

the oxygen being immediately removed by 4 and any known manner with the desired gases or metallic vapours.

At the end of a certain length of time of operation of the apparatus, oxide of mercury may accumulate in the part E passing through the condenser R. In order to clean this part, a simple method, after the removal of the tube A, is to connect the two exhaust tubes C and C by tubing and filling the apparatus with hydrogen, preferably at the same time producing high-frequency discharges in the tube E by means of the small coil usually employed for finding leaks, or producing a luminous discharge therein by means of electrodes suitably placed.

I claim:

1. A process for removing gases evolved from electrodes of a gaseous electric discharge tube during the manufacture of the latter, while the discharge is maintained between said electrodes, which comprises circulating mercury unidirectionally in a closed circuit including the discharge tube, successively converting said mercury from liquid to vapor state in a separate vaporizing receptacle, passing it through substantially the whole longitudinal section of the discharge tube in the vapor state, condensing it by passing downwards through a cooled condensing chamber, and returning it as liquid to the vaporizing receptacle, while causing the gases to flow in the same direction as the condensed liquid, and sucking them from the closed circuit at a point between the condensing chamber and the vaporizing receptacle.

2. A process for removing gases evolved from electrodes of a gaseous electric discharge tube during the manufacture of the latter, while the discharge is maintained between said electrodes, which comprises circulating mercury unidirectionally in a closed circuit including the discharge tube, successively converting said mercury from liquid to vapor state in a separate vaporizing receptacle, passing it through substantially the whole longitudinal section of the discharge tube in the vapor state, condensing it by passing downwards through a cooled condensing chamber, and returning it as liquid to the vaporizing receptacle, while causing the gases to flow in the same direction as the condensed liquid, sucking them from the closed circuit at a point between the condensing chamber and the vaporizing receptacle, and breaking the closed circuit between the vaporizing receptacle and the discharge tube by sealing ofi when the circulation has been continued long enough so that substantially pure mercury vapor issues from the discharge tube.

3. A process for removing gases evolved from electrodes, provided with an electron emissive coating, of a gaseous electric discharge tube and. especially of a high-pressure mercury vapor tube during the manufacture of said tube, while the discharge is maintained between said electrodes, which comprises circulating mercury unidirectionally in a closed circuit including the discharge tube, successively converting said mercury from liquid to vapor state in a separate vaporizing receptacle, passingv it through substantially the whole longitudinal section of the discharge tube in the vapor state, condensing it by passing it downwards through a cooled condensing chamber, and returning it as liquid to the vaporizing receptacle, while causing the gases to flow in the same direction as the condensed liquid, sucking them from the closed circuit at a point between the condensing chamber and the vaporizing receptacle, and maintaining the pressure in the tube sufficiently high to prevent deterioration of the electrodes.

4. An apparatus for removing gases evolved from electrodes of a gaseous electric discharge tube during the manufacture of the latter, while the discharge is maintained between said electrodes, comprising in combination a vaporizing receptacle containing liquid mercury, means comprising a conduit to connect said receptacle to substantially an end of a discharge tube, a second conduit to connect substantially to the opposite end of said tube, the diameters of the two conduits being adapted for their convenient sealing off at said ends, a third conduit, turned downwards, connected to the free end of the second conduit and having its free end submerged in the mercury in the vaporizing receptacle, means for heating the vaporizing receptacle, means for cooling a portion of said third conduit, and a vacuum pump connected to said third conduit at a point between its cooled portion and the vaporizing receptacle.

JEAN LECORGUILLIER.

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