US1688777A

US1688777A - Gas-filled electric incandescent lamp

Info

Publication number: US1688777A
Application number: US231130A
Authority: US
Inventors: Bergmans Jan; M Theodorus Josephus Alphonsus
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1926-12-21
Filing date: 1927-11-04
Publication date: 1928-10-23
Anticipated expiration: 1945-10-23
Also published as: GB359712A; DE535089C; BE374146A; FR703655A

Description

Oct. 23, 1928.

J. BERGMANS El'AL GAS FILLED ELECTRIC rncmmzscam' mu? Filed Nov. 4, 1927 Inventor's Jan B ergmans Theodorus J. AMand Their Attorney.

Patented Oct. 23, 1928.

UNITED STATES PATENT OFFICE.

JAII BERGMANS AND 'I'HEODORUS JOSEI'HUS JACOIBUS ALPHONSUS MANDERS, OF EIND- HOVEN, NETHERLANDS, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPO- BATION 01? NEW YORK.

GAS-FILLED ELECTRIC INCANDESCEN'I LAMP.

Application filed November 4, 1927, Serial No. 231,130, and in the Netherlands December 21, 1928.

The invention relates to an electric incandescent gas filled lamp, such as a projection lamp with a highly concentrated filament and a filling of gas inert to the filament. The filament in such lamps, which have an extremely high light intensity, is heated to very high temperature, with the result that evaporation occurs during which particles emitted from the filament deposit on the inside of the surrounding bulb. Owing to this precipitation of these particles, the inside of the bulb becomes blackened or covered by a soot-like layer, which decreases the brightness of the lamp and causes the lamp to become unsuitable for purposes of illumination. Naturally, this blackening greatly diminishes the efficiency of the lamp and methods have been sought to prevent or diminish it.

One method which has been suggested is to divide the lamp into sections in such a way that the differences in temperature in the different sections cause inside the lamp a flow of gases suifieient to conduct the particles thrown ofi' by the filament into the comparatively large bulb around the filament to some other part of the bulb where they do not have a detrimental influence on the radiation of light. However, this method requires that separate artitions be constructed inside the lam itse f in order to divide it into sections.

T e purpose of the present invention is to secure a forced draft inside the lamp without the use of partitions and without requiring that the lamp be divided into separate sections. To this end the part of the bulb through which the light rays originating from the filament pass has been designed in such a way that it is tubular, surrounds the filament closely and is of comparatively small bore. The concentrated filament is located at the end of the tubular part of the bulb, through which the leads for supplying current to the filament extend. In use the bulb is positioned in such a way that the filament is located in the lower part of the bulb.

The gases, heated directly by the filament, will rise and will be conducted by means of the hot leads which carry the current to the filament to a part of the bulb where these gases may cool off. After this cooling has occurred the comparatively cool gases move downwards, following the inside of the tubular part of the bulb, and thus return to the filament. The cool gases moving downward act as though they surround the upward current of hot gases, and when reaching the lower part of the bulb the cool gases will move with some force along the inside of this lpart which surrounds the filament closely, as

as been mentioned above. Due to the small bore of the tubular part of the bulb immediately surrounding the filament no eddies or vortex motions occur in the currents of gases and, in addition, the desirable result is secured that the currents of gas are extremely swift at this spot so that any black material which tends to deposit there will be scoured off and carried along by the current of gases to another spot where the current is less swift.

In order to secure a good cooling effect at a selected place the tubular part of the bulb may be expanded reatly to form a bulbous or spherical chamdier in the neighborhood of the stem, while the filament is mounted in the end of the tubular part remote from this chamber and as far as possible from the stem.

Two functions result from the expanding of the tubular bulb into a chamber, viz in the first place a cooling chamber is formed, and in the second place a space is secured in which the fast moving gases lose their speed and permit preci itatlon of the particles thrown ofi by the fi ament. In order to increase the cooling artificial cooling may be applied to the bulb in the neighborhood of the stem.

The construction also has the advantage that the filament is surrounded by a tubular glass envelope occupying very little space, while the expanded part of the bulb is located at considerable distance from the filament. Owing to this feature the lamps are very suitable for use for projection purposes. This construction has certain advantages in optical systems using a lens or condenser, as well as in those using a mirror. In the first place, the lens or condenser can be placed much closer to the light source, allowing a more compact construction, and in the second place the expanded part of the bulb is outside the cone of light, so that the light rays are less deformed or weakened. It is, of course, understood that the bulb must be manufactured of a kind of glass which can withstand the high temperatures which are present in the immediate proximity of the filament.

In the accompanying drawing which shows one embodiment of the invention, a concentrated filament 1 is mounted on the ends of a pair of strai ht

parallel leads

2 and 3 which support the filament and also supply current to it through the leading in wires 5 and 6 in the stem and the base 7 which is connected by a socket to a source of current. The filament and the leads are enclosed in a sealed gas filled bulb which contains an inert as and has a bulbous tubular part 8 of smalldiore closely surrounding the filament 1, and. which is expanded into a spherical part or cooling chamber 9 in the neighborhood of the base 7.

When the lamp is lighted the filament 1 located near the sealed end of the tubular part 8 of the bulb will glow and consequently the surrounding inert gas will be heated. A similar heating of the gas takes place between the

leads

2 and 3 which are preferably proportioned to be brought by the normal current flowing through them to a temperature high enough to heat the adjoining and surrounding gas sufiiciently to cause it to ow upwards along the leads. If the lamp is mounted base up so that the base 7 is above the filament 1, either in a slanting or in a vertical direction, then the heated gas will flow upwards along the leads with a velocity great enough to carry alon the particles of filament material and W51 flow into the spherical part or cooling chamber 9 which has a bore so much greater than that of the tubular part 8 that it loses velocity and deposits the particles of filament material. The heated gas is cooled off at the surface of the spherical chamber, whereupon it flows downwards along the sides of the tubular part 8 until it reaches the lower end of the tubular part 8 of the bulb, where it will be again reheated by the filament. As the tubular part of the bulb which immediately surrounds the filament is of small bore, no eddies or vortex motions occur in the currents of gas, which attain a comparatively high velocity, thus preventing the deposition on the bulb walls at this place of articles emitted by the filament. By means 0 this invention the glass of the lampris kept clear for the entire life of the lamp exactly at those places through which the light rays have to pass.

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

1. A gas filled incandescent electric lamp comprising a pair of parallel leads propor- "tioned to be heated by the normal current flowing through them to a temperature sufiicient to cause a flow of the adjoining gas when the lamp is lighted, a concentrated filament on the end of said leads, and a sealed tubular bulb containing inert gas and enclosing said leads and said filament with one end ad acent said filament and of a bore such that when the lam is lighted currents of gas free from eddies ow along said leads and along said bulb walls with a velocity so great that blackening of the bulb walls in the vicinity of the filament is substantially absent.

2. An incandescent electric lamp comprising a sealed bulb having a straight tubular portion closed at one end and expanded near the other end into a bulbous chamber of considerably greater diameter than said tubular portion, a pair of straight parallel leads mounted in said tubular portion and extending from near its closed end into said chamher, and a concentrated filament mounted on the ends of said leads near the closed end of said tubular portion of the bulb, said tubular portion having a bore small enough to cause the currents set up in the gas in the bulb when the lamp is lighted to flow with suflicient velocity to maintain the bulb walls adjacent said filament substantially free from blackenll'l A gas filled incandescent electric lamp comprising a sealed bulb containing an inert gas and having a straight tubular ortion and a portion at one end enlarged to orm a cooling chamber, a stem extending into said cooling chamber, a base on said coolin chamber adjoining said stem, a pair of straight leads secured to said stem to extend through said cooling chamber and into said tubular portion and proportioned to be heated by the normal current flowing through them to a temperature sufiicient to cause the gas to flow along them, and a concentrated filament connected to said leads adjacent the other end of said bulb with a clearance between aid filament and the walls of said tubula portion so slight as to cause high velocity currents of gas free from eddies to flow along the walls of said tubular portion while the lamp is lighted.

4. An incandescent lam com rising a stem, a pair of straight para lel lea s extending from said stem, a concentrated filament on the free ends of said leads, and a sealed bulb containing inert gas and enclosing said leads and filament, said bulb having a bulbous chamber adjacent said stem and surrounding said leads near said stem and a straight tubu lar portion extending from said chamber to enclose said leads and said filament with the opening into said chamber obstructed onl by said leads, said tubular portion having a bore small enough to cause currents in the gas free from eddies and of sufiicient velocity to prevent blackening of its walls near the filament, and said chamber having a bore sufficiently greater to permit the currents to decrease in velocity sufliciently to deposit in said chamber particles of filament material carried by the currents.

' 5. An incandescent electric lamp comprising a sealed bulb having a straight tubular leads near th 1 d d portlonpf small bore closed at one end and tion of the blil en of Sald tubular pm a spherical chamber of conslderable grester In witness whereof, we have hereunto set 10 diameter at the other end, a, pair of straight our hands this 8th day of October 1927.

5 leads extending through the opening of said JAN BERGMANS.

tubular portion lnto said tubular portion, THEODORUS JOSEPHUS JACOBUS and a concentrated filamentmounted on said ALPHONSUS MANDERS.

CERTIFICATE or CORRECTION.

Patent'No. 1,688,777. in Granted October 23, 1928, to

JAN BERGMANS ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, line 15, strike out the word "bulbous" and insert the same before the word "spherical" in line 17; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Oftice.

Signed and sealed this 27th day of November. A. D. 1928.

M. J. Moore, (Seal) Acting Commissioner of Patents.