US2415895A

US2415895A - Manufacture of gaseous discharge tubes

Info

Publication number: US2415895A
Application number: US540770A
Authority: US
Inventors: Lopez Francisco Gonzalez
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1944-06-17
Filing date: 1944-06-17
Publication date: 1947-02-18
Anticipated expiration: 1964-02-18

Description

Feb. 18, 1947.

F. G. LOPEZ MANUFACTUBE OF GASEOUS DISCHARGE TUBES Filed June 17, 1944 iii .5

, smmualz M61560 FONZALEZMPEZ IN VEN TOR,

ATTORNEY Patented eb. 18, 1947 .iJNlTE-D srArEs PAT ENT joFriCs MANUFACTURE OF GASEOUS nrscnAitGE y i TUBES I Francisco (iionzalez Lopea Buenos Air-es, Argentina, assignor, by mesne assignments, to Gen- Elwtflc m ny. Schenectady, N. Y., a I corporation of New York 2 Application mm, 1944, Serial No. 540,770

This invention relates to electric discharge tubes comprising a mercury'va'pour filling and more particularly to a means for dosing the mercury filling within these tubes; f1

In the prior art /of manufacturing electric In orderto obviate the above dimcultie it, has

been suggested by J. L. Cox in his U. S. Patent No. 2,283,189 to enclose the quantityof mercury required for the correct operation of the discharge tube in a roughly sealed metal container or bomb and to mount this container in heatreceiving relationship with respect to one of the filamentary electrodes of the tube. By heating the filament to a convenient temperature the metal containers or bombs are exploded and the enclosed mercury is liberated and penetrates into the tube envelope. 4

But, as already explained hereinabove, the metal containers are only roughly sealed so that during exhaustion mercury vapours may escape and penetrate into the vacuum pumping system unless precautions are taken by inserting mercury traps at adequate points of the exhausting system. Furthermore, the filament used for exploding the metal container has to be overdimensioned in order to withstand the passage of the current necessary for generating the high temperature required. 1

I have now found that the difiiculties referred to above are avoided in a simple manner by making use of an evacuated and hermetically sealed glass ampule enclosing the required quantity of mercury and placed in a metal casing closed by a metal gauze. The metal casing is supported by one of the lead-in wires of the discharge'electrade of the tubes and the mercury is liberated by subjecting the casing to a high-irequency field of considerable intensity so that the ampule cracks open due to the heat generated by the currents induced in the casing.

In the present invention I retain all the advantages deriving from the utilization of the roughly sealed metal container disclosed in the abovementioned patent and in addition provide a means whereby discharge electrodes having normal filaments may be used. Furthermore, since the mercury is enclosed in an evacuated and 4 Claims. (Cl.

hermetically sealed container, the

xhaustion of the tube can be carri ed out as if no mercury were present and the final'fdegree of vacuum .ob-

tained will not be;substan-tiall y altered after the liberation ofQthe mercury; since the dosing ampule "has been evacuated to'the same degree or vacuum as the discharge tube.

' The main ob ector mylinvention is toi provide an improved means. for do the'mercury vapour filling withinjelectricjjdischarge 'tubes in a more accurate and simpler way than has been the caseheretofore.

This and further objects antif'advantages of my invention will become apparentfrom theconsideration of the following detailed description taken in connection with the accompanying drawing which forms part of the specification andin which: v

Fig. 1 isan enlarged longitudinal sectional view through the metal casing containing; the" glass ampule made in accordance 'with this invention.

Fig. 2 is a cross section taken on the lines 2-2 indicated in Fig. 1.

Fig. 3 illustrates a longitudinal section of an electric discharge tube envelope including the mercury vapour dosing means according to the present invention; and finally Fig. 4 is a'lateral view of the portion of the tube envelope including the dosing'ampule according to the present invention.

Referringnow tov the drawing, wherein the same reference characters'indicate like or corresponding parts or elements, it can be seen that the dosing means according to the present invention comprises an evacuated and hermetically sealed glass ampule i0 enclosing a small quantity of mercury ii and placed in a metal casing i2 which is closed .by means of av nickel gauze cover it. A wire it welded to metal casing 52 and to one of the lead-in wires lb of the discharge electrode it, supports the dosing ampule ill and casing 12 within glass envelope ll of the electric discharge tubes. Discharge electrode 18 and opposite electrode I6 are formed of a coil-coiled i of electricdischarge containing dosing ampule I is introduced in a high-frequency field generated within a coil 20 connected to a high-frequency generator 2| and metal casing I2 is heated to relatively high temperature by the eddy currents induced therein, the generated temperature causing dosing ampule to crack open and to liberate the enclosed mercury H which penetrates into the interior of glass envelope I! through the orifices I! of cover l3.

in: discharge electrodes, a source of mercury in said envelope comprising a hermetically sealed glass ampule containing a quantity of mercury and evacuated to the same degree as said envelope, a metal casing enclosing said ampule and having a perforated wall whereby heating of said casing will cause said ampule to befractured to liberated the mercury; and means to support said casing within said envelope.

hermetically sealed envelope containing dis- The cracking of dosing ampule l0 may be facilitated by marking the outer surface thereof with a diamond cutter, as indicated with lines 22 in the drawing of Fig. l.

Thehigh-frequency field to which the metal casing with dosing ampule I0 is subjected is normally adjusted to a value at which only small cracks in ampule III will be produced. However,

- this adjustment is not critical and even an intensity causing dosing ampule ill to break into two or more parts can be used, since these parts will be held together by metal casing I2 and cover l3 and will not penetrate into the interior of envelope II.

It will be appreciated that modifications of the disclosed embodiment of my invention are possible without departing from the spirit of my invention or the scope of the appended claims.

1.'In an electric discharge tube comprising a hermetically sealed envelope containing discharge electrodes, a source of mercury in said envelope comprising an evacuated and hermetically sealed glass ampule containing a quantity of mercury, a metal casing enclosing said ampule and having a perforated wall whereby heating of said casing will cause said ampule to be fractured to liberate the mercury, and means to supportsaid casing within said envelope.

2. In an electric discharge tube comprising a charge electrodes, 2. source of mercury in said envelope comprising an evacuated and hermetically sealed glass ampule containing a quantity of mercury, a sheet metal casing enclosing said ampule and having an open side covered by a metal gauze whereby heating of said casing will cause said ampule to be fractured to liberate the mercury, and means to support said casing within said envelope.

4. In an electric discharge tube comprising an elongated hermetically sealed envelope containing discharge electrodes at its ends. a source of mercury in said envelope comprising an evacuated and hermetically sealed glass ampule containing a quantity of mercury, a metal casing enclosing said ampule and having a perforated wall whereby heating of said casing will cause said ampule to be fractured to liberate the mercury, and means to-support said casing within said envelope adjacent to one end wall of said envelope and with its perforated wall facing said envelope end wall. FRANCISCO GONZALEZ LOPEZ.

REFERENCES CITED The following'references are of 'record in the file of this patent:

hermetically sealed evacuated envelope contain- UNITED STATES-PATENTS 3. In an electric discharge tube comprising a