Gaseous electric discharge device

Nov. 21, 1933.

L. J. DAVIES ET AL

GASEOUS ELECTRIC DISCHARGE DEVICE

Filed July 7, 1932

1,935,697

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INVENTORS

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ATTORNEY

Patented Nov. 21, 1933

1,935,697

UNITED STATES PATENT OFFICE

1,935,697

GASEOUS ELECTRIC DISCHARGE DEVICE

Leonard John Davies and Henry de Boyne Knight, Rugby, England, assignors to General Electric Company, a corporation of New York

Application July 7, 1932, Serial No. 621,256, and in Great Britain July 28,1931

Claims. (Cl. 176—122)

The present invention relates to gaseous electric discharge devices generally and more particularly the invention relates to such devices having a thermionic cathode.

Discharge devices of the kind in which a current of electrons from a thermionic cathode is passed through a gas at a suitable pressure and chemical nature, form a light source of high luminous efficiency, but in the more usual forms 10 of tube are of low intrinsic brilliancy. It is frequently desirable, however, to have a source of small dimensions of high intrinsic brilliancy in order that proper advantage may be taken of reflectors and other light concentrating devices.

It is known that the arc in a discharge device as above set forth can be made to assume small dimensions by a proper adjustment of the gas pressure. Another method is to pass a large , arc current through a tube of small internal di20 ameter. When this is done the device possesses several disadvantageous features. The concentration of the arc into a tube of small dimensions results in the contribution of a considerable amount of energy to the walls of the 25 tube which assume a temperature so high that they are dangerous to touch, and if of glass, soften and eventually collapse. This latter difficulty can be avoided by using quartz as a bulb material, but as is well known, this material is 30 costly and difficult to fabricate into a bulb with lead-in wires.

The object of the present invention, is to provide a discharge device of the kind above set forth which enables a discharge of high intrinsic 35 brilliance to be obtained without the above disadvantages and which is cheap and easy to construct.

In accordance with the invention we provide a tube independent of the enclosing envelope of 40 the device and of small diameter for confining the arc to obtain high intrinsic brilliancy.

In the drawing accompanying and forming part of this specification two embodiments of the invention are shown in which,

Fig. 1 is a front elevational view of one embodiment of the invention, and

Fig. 2 is a similar view of an alternative embodiment of the invention.

Like numbers denote like parts in both figures. 50 Referring to Fig. 1 of the drawing the new and novel gaseous electric discharge device comprises a glass container 1, such as a lead or lime glass container having a gaseous atmosphere therein, such as neon, and a thermionic cathode 55 3 of the Pirani type sealed in at one end thereof and a metal anode 2 sealed into the opposite end thereof. Current inleads 4 and 5 for said electrodes 2 and 3 respectively are sealed into stems 10 and 11 respectively. A shield 6 consisting of the same glass as said container 1 is fused to 6* said stem 10 at the anode end of said container 1 and a spiral tube 7 of quartz or other light transmitting, heat resisting material is joined to said shield 6 and supported by the frictional joint represented at 16 between said shield 6 and eo said tube 7. Said shield 6 encloses the anode 2 and the current inlead 4 thereof and the tube 7 joined thereto extends up to within a short distance of said cathode 3. By virtue of this structure the arc current must pass to said anode 2 70 through said tube 7 and not outside said tube 7. The internal diameter of said tube 7 from the joint 16 to the end thereof is comparatively small so that the luminous arc confined therein is of liigh intrinsic brilliancy. Since the junction or 75 joint 16 between the quartz tube part 7 and the glass shield 6 need not be a vacuum tight junction, but only close fitting, fabrication is easy.

The embodiment of the invention shown in Fig. 2 is in all respects similar to that shown in so Fig. 1 except the shield 6 is fused to the wall of said container 1, said tube 7 is straight and terminates at a greater distance from the cathode 13 and in the constricted part 8 of said container 1. The device shown in Fig. 2 is adapted to 35 operate on alternating current, and two thermionic electrodes 13 and 15 are provided at each end thereof for this purpose. Said electrode 13 is of the Wehnelt type and said electrode 15 is of the self-heating Pirani type. Both 90 electrodes are of the same type where that is desired.

while we have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood 95 that various omissions, substitutions and changes in the forms and details of the device illustrated and in its use and operation may be made by those skilled in the art without departing from the broad spirit and scope of the invention. 100