Electric lamp and discharge devices – With gas or vapor – Incandescent filament lamp
Patent
1996-11-25
1998-09-22
Oen, William L.
Electric lamp and discharge devices
With gas or vapor
Incandescent filament lamp
313344, 313580, H01K 150
Patent
active
058119345
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an electric incandescent lamp, and more particularly to an incandescent halogen lamp having a rotation-symmetrical bulb or envelope, and to filaments that are suitable for such incandescent lamps.
BACKGROUND
Incandescent halogen lamps, both in general lighting and for special lighting purposes, are often used in combination with a reflector, such as in projection technology.
The rotationally symmetrical form of the lamp bulb or envelope, combined with an infrared-radiation-reflecting coating--hereinafter called an IR layer for short--applied to the inner and/or outer surface of the bulb has the effect that a majority of the IR radiation power produced by the filament is reflected back. The resultant increase in lamp efficiency can be utilized to increase the temperature of the filament and consequently the light flux, if the electrical power consumption is constant. On the other hand, a given light flux can be attained with less electrical power consumption--an advantageous "energy-saving effect". Another desirable effect of the IR layer is that markedly less IR radiation power is emitted through the bulb, heating the environment, than in conventional incandescent lamps.
Because of unavoidable absorption losses in the IR layer, the power density of the IR radiation components inside the bulb decreases with the number of reflections, and consequently the efficiency of the incandescent lamp drops also. It is therefore decisive for the actually attainable increase in efficiency to minimize the number of reflections required to return the individual IR rays to the filament.
This type of lamp is disclosed for instance in U.S. Pat. No. 4,160,929Thorington et al., European Patent EP A 0 470 496, and German Patent Disclosure DE-OS 30 35 068. U.S. Pat. No. 4,160,929 teaches that to optimize lamp efficiency, the geometric shape of the filament must be adapted to that of the bulb. Moreover, the filament must be positioned as exactly as possible in the optical center of the bulb.
As a result, a wave front originating at the surface of the filament is reflected back, unimpeded, by the bulb surface. Aberration losses are consequently minimized. A spherical bulb, for instance, should in an ideal case have a centrally located and likewise spherical filament. Because of the limited ductility of the tungsten wire that is used as a rule, however, coil shapes for this purpose are attainable only to a greatly limited extent. A cubelike coil has been proposed as a rough but practical approximation for a sphere. In another embodiment, the coil has its largest diameter in its middle. That diameter decreases successively toward the two ends of the coil. For an ellipsoid bulb shape, it has been proposed that one filament be located at each of the two focal points of the ellipsoid.
EP A 0 470 496 discloses a lamp with a spherical bulb, with a cylindrical filament located in the center. This reference teaches that the losses of efficiency from the deviation of the filament from the ideal spherical shape can be kept acceptably low on the following preconditions. Either the bulb diameter and filament diameter or length must be adapted carefully to one another within a tolerance range, or the diameter of the filament must be markedly less (less than a factor of 0.05) than that of the bulb. A lamp with an ellipsoid bulb in whose focal line an elongated filament is axially arranged is also disclosed.
German Patent Disclosure DE-OS 30 35 068 provides teaching for the sake of minimizing the aberration losses, which even in the last embodiment above are unavoidable. In this disclosure, the two focal points of the ellipsoid bulb are located on the axis of the cylindrical filament and at predetermined distances from its respective ends.
THE INVENTION
The object of the invention is to overcome the disadvantages mentioned and to disclose an incandescent lamp that excels in having an efficient return of the emitted IR radiation to the filament and consequently high efficiency. Moreover, compa
REFERENCES:
patent: 2462858 (1949-03-01), Glauber
patent: 3134691 (1964-05-01), Kopecky
patent: 3255375 (1966-06-01), Ward
patent: 4283653 (1981-08-01), Brett
patent: 4375605 (1983-03-01), Fontana
patent: 5550423 (1996-08-01), Oughton
Binder Ulrich
Bunk Axel
Hollstein Andreas
Noori Max H.
Oen William L.
Patent-Treuhand-Gesellschaft fur elektrische Gluhlampen mbH
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