Title:
Electric discharge lamp
United States Patent 2207133


Abstract:
This invention relates to electric discharge lamps and more particularly to lamps of the high vapor pressure type similar to those disclosed in the United States Patent 2,094,694 issued r October 5, 1937. Such lamps are usually made with envelopes of quartz or high melting point glass, and...



Inventors:
Scott, William J.
Bourne, Harry K.
Application Number:
US23865038A
Publication Date:
07/09/1940
Filing Date:
11/03/1938
Assignee:
GEN ELECTRIC
Primary Class:
Other Classes:
313/239, 313/242, 313/595, 313/623
International Classes:
H01J61/10
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Description:

This invention relates to electric discharge lamps and more particularly to lamps of the high vapor pressure type similar to those disclosed in the United States Patent 2,094,694 issued r October 5, 1937. Such lamps are usually made with envelopes of quartz or high melting point glass, and we have observed that the material in the neighborhood of the electrodes is frequently attacked and devitrifled.

11i The object of this invention is to provide means for preventing this devitrification, and to that end it consists in providing means for protecting the wall of the envelope in the vicinity of the cathode from sputtering which may cause de1 . vitrification and from heat radiation from the cathode. This means may consist of a shield between the cathode and the wall of the lamp such as a cylinder or sleeve of refractory material, for example, of tungsten, molybdenum or quartz. The material forming the wall of the envelope will then be protected from sputtered material from the cathode, and the devitrification will be reduced owing to the temperature of the wall being reduced, and owing to the shielding from the discharge and the sputtered material.

In the drawing accompanying and forming part of this specification three embodiments of the invention are shown in which 80 Fig. 1 is a side elevational, partly sectional view of one embodiment of the invention, Fig. 2 is a similar view of another embodiment of the invention, and Fig. 3 is a similar view of still another embodi3s ment of the invention.

Referring to the drawing the gaseous electric discharge device comprises a tubular envelope I of quartz, into which an electrode 2 is sealed.

Before sealing the electrode into the envelope it is first sealed into a cylinder 3 of quartz, which is then sealed into the envelope I in such manner that the walls of the cylinder are in close proximity to but not in actual contact with, the walls of the envelope 1. It will be understood, of course, that the other end of the device is similar in structure to the end shown in the drawing.

The electrodes are preferably thermionic, activated electrodes which serve alternately as anode and as cathode when the device is operated on alternating current. The sealed envelope I has a starting gas therein, such as argon, and a quantity of metal, such as mercury, the vapor of which is luminosity producing during the operation of the device. In Fig. 2 a sleeve 4 of tungsten or molybdenum is inserted in the envelope I, so that it surrounds the electrode 2. When* the sleeve is made of metal, as in this case, it may be utilized as a starting or auxiliary electrode by providing a current lead therefor.

In the construction illustrated in Fig. 3 a thin sleeve of molybdenum or other suitable refractory metal 4 is sealed between an inner quartz sleeve 3 and the outer envelope I so that it forms U a barrier which will prevent devitrification from spreading from the inner quartz shield to the outer envelope. In this case the metal sleeve may be utilized as an electrode.

What we claim as new and desire to secure by 0 Letters Patent of the United States, is: 1. An electric discharge lamp of the high pressure type comprising a tubular envelope of vitreous material, electrodes sealed therein at the ends thereof, a vaporizable material therein, and U a sleeve of refractory metal fused into the end of said envelope and surrounding one of said electrodes, part of the vitreous material of said envelope being interposed between said electrode and said metal sleeve and covering the major 00 portion of the inner surface of said sleeve, said sleeve preventing devitrification of said envelope in the region of said electrode.

2. An electric discharge lamp of the high pressure type comprising a tubular envelope of vitre- U ous material, electrodes sealed therein at the ends thereof, a vaporizable material therein, and a sleeve of refractory metal fused into the end of said envelope and surrounding one of said electrodes, part of the vitreous material of said envelope being interposed between said electrode and said metal sleeve and covering the major portion of the inner surface of said sleeve, said sleeve being an auxiliary electrode and preventing devitrification of said envelope in the region of said electrode.

WILLIAM J. SCOTT.

HARRY K. BOURNE.