US2215300A - High-pressure metal-vapor electric discharge device - Google Patents

Description

Sept. 17, 1940- J.W. RYDE 2,215,300

HIGHYRE-SSURE METAL-VAPDR ELECTRIC DISCHARGE DEVICE Filed July 26, 1939 INVENTOR John W]? de BY 6M TORNEY Patented Sept. 17, 1940 UNITED STATES PATENT OFFICE HIGH-PRESSURE METAL-VAPOR ELECTRIC DISCHARGE DEVICE John W. Ryde, Wembley, England, assignor to General Electric Company, a corporation of New York Application July 26, 1939, Serial No. 286,697 In Great Britain July 29, 1938 2 Claims.

This invention relates to high-pressure metalvapor electric discharge devices of the type wherein, in full operation, the pressure of the vapor exceeds five atmospheres and the distance between the terminations of the discharge path is much less than any internal dimension of the envelope in a plane perpendicular to and passing through the straight line joining the said terminations. It relates also to their'manufacture.

Devices of this type may burst in operation under abnormal conditions. It is easy to make the main part of the envelope strong enough to stand the internal pressure so long as it is in its original state; but convection currents playing on it are apt to devitrify or otherwise weaken it.

Damage by convection streams could be prevented by providing shields which disperse the streams and prevent them impinging on the envelope. The shields might be of the same material as the envelope and therefore be damaged by the streams incident on them; but this damage would not matter, since the shields are subject to little stress and can be placed out of the path of the useful light. On the other hand, it is difiicult to provide adequate shields; for they are to be introduced through apertures in the envelope; if these apertures are wide enough to admit the shields, they may themselves introduce weakness.

The object of this invention is to provide shields that can be introduced through narrow apertures in the envelope subsequently filled, for example, by the seals carrying the leading-in-conductors and that yet protect the envelope sufllciently. Another object of the invention is to provide a method of manufacture for lamps of the above type. Still further objects and advantages attaching to the device and to its use and operation will be apparent to those skilled in the art from the following particular description.

According to the invention a device of the type specified comprises one or more strips of vitreous material, of substantially the same coemcient of thermal expansipn as the envelope, fused to the envelope and located so that, in some position (not necessarily or preferably all positions) of the device, they lie above the line between the terminations of the discharge path. A strip may be fused to the envelope at its edges or corners; or beads or the like may be inserted between the envelope and the strip, fused on one side to the envelope and on the other to the strip.

The strips can be introduced lengthwise through a narrow aperture, guided into position and fixed thereby heating the envelope where they rest on it. Several strips may be thus arranged side by side and/or end to end, so that they make up a continuous shield of area greater than that of any single strip. Again several isolated strips, or combinations of strips, may be provided at different parts of the envelope, so as to receive the convection streams when the lamp is operated in different positions. The strips must not be so close to thedischarge path that they are raised to a temperature at which they evaporate appreciably.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in a side elevational, partly sectional view. The lamp illustrated in the drawing is capable of dissipating 500 watts during operation and comprises a spherical envelope l of quartz, for example, having an internal diameter of about 40 mm. and a wall thickness of about 3 mm. The thermionic electrodes 2, 2 lie along a diameter and are spaced 5 mm. apart symmetrically about the centre. The apertures, finally closed by the seals 3, 3 carrying the main electrodes, were originally 8 mm. in diameter. Each shield 4 or 5 consists of a strip of quartz of approximately 8 x 25 x 1.5 mm., introduced through one of these apertures. A single strip of this kind is usually sufficient to protect the envelope from the convection streams in any one position of the lamp; but two shields mounted end to end are sometimes preferable. Strips 4 and 5 are in mutually perpendicular planes, so that the lamp can be operated in two positions diflering in rotation through a right angle about a diameter of the envelope. The strips are fixed to the envelope at their corners by fusion.

The envelope tcontains a starting gas, such as argon or neon, and a quantity of mercury in an amount such that the lamp is capable of operation with a mercury vapor pressure inexcess of five atmospheres.

While I have shown and described and have pointed out in the annexed claims certain novel features of the invention, it will be understood 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.

What I claim as new and desire to secure by Letters Patent of the United States, is:

l. A gaseous electric discharge lamp comprising a generally spherical container which is constituted of vitreous material and which encloses spaced electrodes, said' container having in the wall thereof an opening of a diameter which is only a minor fraction 01' the diameter of the container itself, a lead-in conductor for one 01' said electrodes extending through the opening and supported therein by a body of vitreous material which completely closes the opening, a quantity of an ionizable medium in the container in an amount such that the lamp is capable of operation with an internal pressure of at least several atmospheres, and a narrow strip oi vitreous material mounted in the container substantially parallel to and oi'i'set from a straight line drawn between the said electrodes for preventing devitriflcation-oi the portion of the container subtended bythestrimthesaidstripbeingofsuchlimited dimensions that it is capable of being introduced into the container through the said wall opening prior to sealing the said closure body therein.

2. A gaseous electric discharge lamp comprising a generally spherical container which is constituted of vitreous material and which encloses spaced electrodes, said container having in the wallthereoianopeningoiadiameterwhichis only a minor traction of the diameter of the container itself, a lead-in conductor for one or said electrodes extending through the opening and supported therein by a body 0! vitreous material which completely closes the opening, a quantity of an ionizable metal in the container in an amount such that the lamp is capable or operation with an internal pressure of at least five atmospheres, and a substantially planar strip of vitreous material fused at its extremities to the inner wall oi the container so that the portion of the container subtended by the strip is shielded from convection currents occurring in the gaseous atmosphere of the lamp during operation thereof, the said strip beingoisuchlimited dimensionsthatitiscapabie 01! being introduced into the container through thesaidwallopeningpriortosealingthesaid closure body therein and having approximately the same coemcient of expansion as the material of said container.

JOHN W. RYDI.

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