Electric lamp and discharge devices – With optical device or special ray transmissive envelope – Reflector
Patent
1998-09-11
2000-12-12
Patel, Nimeshkumar D.
Electric lamp and discharge devices
With optical device or special ray transmissive envelope
Reflector
313110, 313573, 313634, 313635, H01J 6140
Patent
active
061603414
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention proceeds from an incandescent lamp, in particular a halogen incandescent lamp having an IR reflective layer in accordance with the preamble of claim 1.
This type of lamp is used both in normal lighting systems and for special lighting purposes and also, in combination with a reflector, in projection technology, for example.
In conjunction with a layer which is applied to its inner and/or outer surface and reflects IR radiation--referred to below for short as IR layer--, the rotationally symmetrical shape of the lamp bulb has the effect that a major part of the IR radiant power radiated by the luminous element is retroreflected. The rise thereby achieved in the lamp efficiency can be used, for one thing, to increase the temperature of the luminous element for a constant electric power consumption, and therefore to increase the luminous flux. On the other hand, a prescribed luminous flux can be achieved with a smaller electric power consumption--an advantageous "energy-saving effect". A further desirable effect is that because of the IR layer much less IR radiant power is radiated through the lamp bulb, and so the environment is heated much less than with conventional incandescent lamps.
Because of the unavoidable absorption losses in the IR layer, the power density of the IR radiation components inside the lamp bulb decreases with the number of reflections, and therefore so does the efficiency of the incandescent lamp, as well. Consequently, what is decisive for the increase in efficiency which can actually be achieved is to minimize the number of reflections required for returning the individual IR rays to the luminous element. The lamp bulb provided with the IR layer is specially shaped for this purpose.
PRIOR ART
This type of lamp is disclosed, for example, in U.S. Pat. No. 4,160,929, EP-A 0 470 496, DE-A 30 35 068 and DE-A 44 20 607. U.S. Pat. No. 4,160,929 teaches that optimization of the lamp efficiency requires the geometrical shape of the luminous element to be adapted to that of the lamp bulb. Moreover, the luminous element should be positioned as exactly as possible at the optical center of the lamp bulb. As a result, a wave front emanating from the surface of the luminous element is retroreflected undisturbed at the bulb surface. Aberration losses are thereby minimized. In the ideal case, a spherical lamp bulb, for example, should have a centrally arranged, likewise spherical luminous element. However, because of the restricted ductility of the tungsten wire generally used therefor, appropriate filament shapes can only be realized in a very limited fashion. A cubic filament is proposed as a coarse but feasible approximation to a sphere. In a further embodiment, the filament has the largest diameter at its center. Said diameter decreases successively towards both ends of the filament. It is proposed for an ellipsoidal bulb shape to arrange one luminous element each at the two focal points of the ellipsoid.
EP-A 0 470 496 discloses a lamp with a spherical bulb at the center of which a cylindrical luminous element is arranged. This reference teaches that the loss in efficiency owing to the deviation of the luminous element from the ideal spherical shape can be limited to an acceptable degree under the following preconditions. Either the bulb diameter and luminous element diameter or length must be tuned to one another carefully inside a tolerance range, or else the diameter of the luminous element must be conspicuously smaller (smaller by a factor of 0.05) than that of the lamp bulb. Moreover, a lamp with an ellipsoidal bulb is specified on whose focal line an elongated luminous element is axially arranged.
DE-A 30 35 068 specifies a teaching on minimizing the aberration losses, which are also unavoidable in the case of the last named embodiment. According to this reference, the two focal points of the ellipsoidal lamp bulb are on the axis of the cylindrical luminous element and at prescribed distances from the respective ends thereof.
Finally, DE-A 44 20 607 disclo
REFERENCES:
patent: 4041344 (1977-08-01), LaGiusa
patent: 4160929 (1979-07-01), Thorington et al.
patent: 4988911 (1991-01-01), Miller
Binder Ulrich
Mueller Sigbert
Bessone Carlo S.
Patel Nimeshkumar D.
Patent-Treuhand-Gesellschaft Fuer Elektrische Gluehlampen MBH
Williams Joseph
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