US2145105A - Electric incandescent lamp and similar device - Google Patents

Description

Jan. 24, 1939. J. AlscH ET AL 2,145,105

ELECTRIC INCANDESCENT LAMP AND SIMILAR DEVICE Filed April 27, 1937 Inventors: Johannes Aiscln,

Heinrich Asmus en,

Their Attorney.

Patented Jan. 24,1939

UNITED STATES ELECTRIC INCANDESCENT LAMP AND SIIHILAR DEVICE Johannes Aisch,- Falkensee, near Berlin, and Heinrich Asmussen, Bci-lin-Steglitz, Germany, assignors to General Electric Company, a corporation of New York Application April 27, 1937, Serial No. 139,290

Germany May 5,

2 Claims. (01. 176-38) Our invention relates to electric. incandescent lamps and similar devices comprising a sealed envelope containing an electric energy translation element. More particularly our invention relates to such devices provided with one or more fuses for preventing the formation of arcs.

In gas-filled electric lamps, particularly those having double or multiple coiled tungsten filaments, there is the possibility of the formation w of an arc within the envelope upon breakage of the filament with the resulting rise in current which may cause rupturing of the main line fuse thereby causing all the lamps connected in the same circuit to be extinguished. In order to avoid this, such gas-filled incandescent lamps have heretofore been equipped with fuses to limit the current. The said fuses are generally in the form of a very thin wire of, for example, a nickel alloy, which is incorporated in one or more of 20 the leading-in wires. In one such construction a portion of a lead wire between the envelope and the base terminal constitutes a fuse. When this fuse melts a small arc is frequently formed within the base and this are may lead to explo- 25 sions if the lamp is located in a gaseous atmosphere such as in mines or factories, since the gas enters the base which is not hermetically sealed.

According to this invention, the'above-men- 3o tioned disadvantages are obviated by surrounding the fuse with a tube of vitreous material such as glass which is sealed preferably by fusion at both ends to the lead wire to form a hermetically sealed enclosure for the fuse. With such an arrangement a high gas and vapor pressure is formed within the tube at the instant that the fuse wire is ruptured. This high gas and vapor pressure is produced by the intense heating of the air and also from the evaporation of the fuse 40 wire. Generally the high gas and vapor pressure entirely prevents the formation of an arc within the vitreous tube, but in any case the arc is extinguished immediately upon its formation thereby eliminating the danger of an explosion of the 45 gases which have penetrated into the base from the space surrounding the lamp.

It has been suggested heretofore to cover the fuse within the base with an insulating coating of zirconium silicate, or to embody it in the solidified basing cement which serves as an insulator. Such materials, however, are somewhat porous and therefore do not entirely eliminate the danger of explosions. There is also danger of the said coatings being fractured upon rup- 55 turing of the fuse.

Other features and advantages of this invention will appear from the detailed description thereof and from the drawing.

The drawing is an elevation broadly in section of an incandescent lamp comprising my invention.

Referring to the drawing, the lamp comprises a glass bulb I which is filled with an inert gas or gases such as a mixture of argon and nitrogen or, carbon and nitrogen. The lamp is provided with the usual mount comprising a stem tube 2, arbor 3 and exhaust tube 4. The ends of the coiled coil filament 6, which is supported on support wires 5, are attached to the inner ends of lead wires 1, I which are in turn secured to the press leads 9, 9' which are sealed in the stem press 8. Two thin wires l0, H) of an alloy having a low melting point, such as a nickel alloy, are secured to the opposite ends of the said press leads 9, 9'. The said thin wires l0, Ill constitute the fuses for the'lamp. The outer ends of u said wires III, III are connected to the base shell l2 and end contact l3 by means of wires H, II

of copper, for example. Glass tubes M, It surround the said fuse wires Ill, Ill and have their ends sealed by fusion to the adjacent ends of the wires 9, 9' and H, II' so that the said fuse wires are wholly enclosed in the said tubes l4, l4 and are surrounded by a relatively small quantity of enclosed air.

The invention may of course be used in various types of lamps such as tungsten arc lamps, vapor discharge lamps and photofiash lamps, and also for discharge tubes, high capacity rectifiers and X-ray tubes. Instead of incorporating a fuse in each of the lead wires, it is of course possible to incorporate a fuse in only one of the said wires, or when there are more than two lead wires, to employ fuses in only a few of them. Each fuse may consist of a thin metal strip having a low melting point instead of being made of thin wire.

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

1. An electrical device comprising a. sealed envelope, a base on said envelope, an electric energy translation element in said envelope, lead wires 5 extending through said envelope and electrically connected to said translation element, the outer ends of said lead wires extending to terminals on said base, a portion of at least one of said lead wires between said envelope and said base constituting a fuse, and a tube of vitreous material surrounding said fuse and sealed by fusion at both ends to said lead wire at points beyond the ends of said fuse portion to hermetically enclose said fuse. u

between said envelope and said base constituting a fuse. and a tube of vitreous material surroundmg each of said fuses and sealed by fusion at both ends to the lead wire surrounded thereby at points beyond the ends of the fuse portion to hermetically enclose said fuses.

J OHANNES AISCH. HEINRICH ASMUSSEN.

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