US3435272A

US3435272A - Tubular halogen cycle incandescent lamp with inner cylinder for universal operation

Info

Publication number: US3435272A
Application number: US565457A
Authority: US
Inventors: David H Green
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1966-07-15
Filing date: 1966-07-15
Publication date: 1969-03-25
Anticipated expiration: 1986-03-25

Description

March 25, 1969 Fig 3/? IOD/NE CO/VCENTEflT/ON Fig). 4

D. H. GREEN 3,435,272 TUBULAR HALOGEN CYCLE INCANDESCENT LAMP WITH INNER CYLINDER FOR UNIVERSAL OPERATION Filed July 15, 1966 UPPEEEND a 2 a INTERN/9L LENGTH, [NC/1'55 ITWVEETWTOT'I David HGT-sen y am .f"

His Adv-kc neg United States Patent US. Cl. 313-222 5 Claims ABSTRACT OF THE DISCLOSURE In an elongated tubular incandescent lamp of the halogen cycle type, with an axial filament and containing an inert fill gas and a halogen getter, thermal separation of the halogen and the fill gas in vertical operation of the lamp, is effectively minimized by a transparent cylinder concentrically arranged between the filament and the lamp envelope.

This invention relates generally to electric incandescent lamps, and more particularly to incandescent lamps of the halogen cycle type comprising an elongated tubular envelope containing an axially extending tungsten filament and a filling of inert gas together with halogen gas or vapor which functions as a regenerative getter to return to the filament tungsten vapor evolved therefrom during operation of the lamp to thereby prevent deposition of the tungsten vapor on the envelope wall as a dark coating. Such lamps, in which the halogen is iodine, are more fully disclosed and claimed in Patent 2,883,571 to Fridrich and Wiley.

Although such lamps have come into use with eminently successful results, when they are operated in positions inclined from the horizontal the iodine and inert gas separate, with the iodine tending to go to the bottom of the lamp. In some cases there is not enough iodine at the top of the lamp to prevent tungsten blackening. This problem is particularly acute in lamps having desirable internal diameters of less than about 20 mm. and greater than about 4 mm. and a length greater than about three times the diameter wherein there is a laminar flow of the inert gas upwardly along the filament and downwardly along the envelope wall. The phenomenon apparently occurs because the lamp when burned vertically, or inclined as little as about 4 from the horizontal, acts as a thermal separation column. The iodine tends to diffuse radially toward the envelope wall and the convective motion of the inert fill gas tends to pump it toward the bottom.

It is therefore an object of the present invention to provide a novel construction which will permit operation of the lamp in any position, including the vertical, by making the distribution of halogen more uniform along the length of the lamp. It is a further object to achieve that result without the need for excessive amounts of halogen which tend to minimize the difficulty by simply providing more halogen throughout the envelope, but which can absorb a significant amount of light or, in some cases, attack portions of the filament and support members.

In accordance with the invention the halogen separation is effectively decreased by providing a light-pervious cylinder or sleeve concentrically disposed in the lamp envelope between the upward and downward path of the gas flow. The cylinder efiectively blocks one of the mechanisms of the separation phenomenon. Convective fiow of the fill gas still occurs with the gas moving upwardly within the inner cylinder and downwardly in the annular space between the cylinder and the inner envelope wall. However, the difiusion of the halogen radially toward the Patented Mar. 25, 1969 envelope wall is blocked by the inner cylinder, thereby preventing the downward moving stream of fill gas from carrying the halogen to the bottom of the envelope.

Further features and advantages of the invention will appear from the following detailed description and from the drawing wherein:

FIG. 1 is a side elevation, in section, of a lamp comprising the invention;

FIG. 2 is a schematic pictorial view of the lamp illustrating the convective flow of the fill gas;

FIG. 3 is a chart showing an experimental determination of the distribution of halogen over the length of a lamp containing iodine as the halogen; and

FIG. 4 is a cross section of the lamp.

Referring to FIG. 1 of the drawing, the lamp illustrated therein comprises a tubular envelope 1, preferably of essentially fused silica or quartz, having therein an axially extending filament 2 of helically coiled tungsten wire. The filament is connected at respective ends, in this case, by straightened end or leg portions 3 of the filament wire, to extremely thin strips of foil 4, preferably of molybdenum, which are hermetically sealed in pinch seal portions 5 at respective ends of the envelope, and which are, in turn, connected to outer lead wires 6 which may also be of molybdenum.

The envelope 1 also contains a filling of inert gas such as nitrogen, argon, krypton or xenon, or mixtures thereof, preferably at a pressure of at least several hundred torr (mm. Hg), and also a small quantity of halogen. The filling of gas and halogen may be introduced by way of an exhaust tube the residue of which is shown at 7. When the halogen is iodine, it is preferably introduced in elemental form along with a small amount of oxygen which is usually added with the inert fill gas as disclosed, for example, in Patent 3,160,454 to Zubler et a1. When -a halogen other than iodine is used, it is preferably introduced as a compound containing hydrogen, such as hydrogen bromide, or a halogen derivative of hydrocarbons, such as methyl or methylene bromide.

In accordance with the invention, in the vertical operation of lamps having tubular envelopes, especially those of internal diameters within a range greater than 4 millimeters and less than 20 millimeters, separation of the iodine or other halogen from the inert gas is significantly prevented or minimized, and early bulb blackening is avoided, by placing within the envelope 1 a concentrically arranged, open ended, cylinder 8 which may also be of quartz and which preferably extends along at least the full length of the coiled filament 2. The cylinder or sleeve 8 is herein illustrated as being supported by a pair of short quartz rods or spuds 9 which are tacked or fused to the envelope 1 and cylinder 8. When desired, the filament 2 is provided with conventional auxiliary tungsten wire spiral supports spaced along the length of the filament and engageable with the inner wall of the cylinder 8.

As illustrated in FIG. 2, during operation of the lamp there is a laminar flow of the fill gas upwardly along the filament 2 within the cylinder 8 and downwardly along the envelope 1 and outside the cylinder 8, as indicated by the arrows. However, diffusion of the halogen radially toward the wall of the envelope 1 and into the downward flow of the fill gas, is blocked by the cylinder 8 so that vertical separation of the halogen is effectively decreased and much more uniformly distributed along the length of the lamp.

The cylinder 8 is correctly positioned when the annular cross sectional area A1 (FIG. 4) between the filament 2 and cylinder 8 is approximately equal to the annular cross sectional area A2 between the cylinder 8 and envelope 1.

By way of example, a 500 watt, volt lamp as shown in FIG. 1 and having an envelope 1 of inch nominal outside diameter (about 7.5 millimeter inside diameter) and an inner envelope length, between the seals 5, of 3 inches, was provided with an inner cylinder 8 of about 5 mm. inside diameter and 5.5 mm. outside diameter. The lamp was filled with argon at a pressure of 1,760 torr, and a small amount (about 3 micromoles) of iodine were added. The iodine had been doped with a trace of iodine-131 which is a radioactive gamma ray emitter. Thus the iodine distribution could be measured while the lamp was lighted by counting the gamma rays.

The iodine distribution during vertical operation of the lamp was found to be quite uniform along the length of the cylinder 8 as shown in the FIG. 3 chart wherein the abscissa is internal lamp length, in inches, and the ordinate is iodine concentration in arbitrary units. The upper end of the lamp is to the right in FIGS. 1 and 3. The iodine concentration of the improved lamp comprising the invention is shown by the dotted line curve A, in comparison with the concentration in an otherwise similar standard lamp without the cylinder 8 as shown by the solid line curve B. The standard lamp would tend to blacken at the top because of insutficient iodine. The concentration of the improved lamp remains effectively uniform for all lamp orientations from vertical to horizontal, so that the lamp is universally operable in any position.

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

1. A halogen cycle electric incandescent lamp comprising a light-pervious elongated tubular envelope containing a coiled tungsten wire filament extending axially of said envelope and a filling of inert gas and halogen wherein, in a position of the lamp inclined from the horizontal, there is a laminar flow of the gas in opposing paths upwardly along the filament and downwardly along the envelope wall together with migration of the halogen radially toward the envelope wall to a position to be swept downward to the bottom of the envelope by the downward flow of the gas, and means to block the radial migration of the halogen comprising an open ended lightpervious imperforate cylinder concentrically disposed in said envelope between the upward and downward paths of the gas flow and coextensive With the coiled filament and providing a generally uniform distribution of the halogen along the length of said cylinder irrespective of the inclination of the lamp during operation.

2. A halogen cycle electric incandescent lamp as in claim 1 wherein the halogen is iodine.

3. A halogen cycle electric incandescent lamp as in claim 1 wherein the halogen is iodine and the inert gas is argon.

4. A halogen cycle electric incandescent lamp as in claim 1 wherein the halogen is bromine.

5. A halogen cycle electric incandescent lamp as in claim 1 wherein the halogen is bromine and the inert gas is argon.

References Cited UNITED STATES PATENTS 2,211,597 8/1940 Dorgelo et al 3l3222 X 2,530,990 11/1950 Peters. 2,883,571 4/1959 Fridrich et a1 313222 X JAMES W. LAWRENCE, Primary Examiner.

DAVID OREILLY, Assistant Examiner.

U.S. Cl. X.R.