Electric lamp and discharge devices – With gas or vapor – Envelope with particular structure
Patent
1998-12-23
2000-10-31
Patel, Vip
Electric lamp and discharge devices
With gas or vapor
Envelope with particular structure
313493, H01J 6130
Patent
active
061407690
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an electric incancescent lamp comprising:
a moulded glass plate which is connected in a gastight manner to current conductors and to a metal tube which extend through said plate;
an incandescent body occupying a predetermined position relative to the moulded plate and connected to the current conductors;
a glass bulb around the incandescent body, connected in a gastight manner to the moulded plate by means of enamel;
a filling gas having a pressure of at least 1 bar inside the bulb,
said metal tube having a gastight seal outside the bulb.
Such an electric incandescent lamp is known from FR-B-913,579.
The known lamp has a moulded or pressed glass plate with a circular edge with a locating stud thereon. The lamp is designed for being passed with its bulb in front through an opening in a reflector and for being pressed home with the edge of the plate against a boundary of said opening. The reflector with the lamp may be used as a motor vehicle headlamp for generating a passing beam and a driving beam.
It is a disadvantage of the known electric lamp that the glass plate can only be manufactured with wide dimensional tolerances. This means that the position of the incandescent body is also badly defined.
It is desirable in other applications of incandescent lamps, for example at the rear of vehicles such as motor cars, to have available electric incandescent lamps which can be moved backwards, i.e. with a lamp cap or base in front, against a carrier, and whose incandescent body then occupies an accurately defined position relative to this carrier with the bulb facing away from the carrier. Such lamps may be used for the stop light, the tail light, the reversing light, the rear fog lamp, the indicator lights, etc.
Known electric incandescent lamps for these functions are provided with lamp caps. The incandescent body thereof has a position which is defined within no more than wide limits relative to said lamp cap, and the lamps have a comparatively short life. In addition, there is a comparatively high early failure rate owing to lamp leaks.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an electric incandescent lamp which renders possible an accurate, predetermined position of the incandescent body relative to the glass plate as well as a compact construction.
According to the invention, the glass plate is a sintered body which has a composition which corresponds to the composition of the glass of the bulb.
The sintered glass plate can be manufactured to a high dimensional accuracy. The current conductors and the metal tube may be present right from the start and may be passed through the glass in a gastight manner in that case. The sintered glass plate has the further advantage that it has a light color, for example white or a pale grey, so that it reflects incident light. It is prevented thereby that the light incident thereon is lost to the light beam which may be formed by means of a reflector. The correspondence in glass compositions avoids glass strain.
The lamp has a comparatively long life thanks to the filling gas pressure above 1 bar. It is favorable to choose the pressure of the filling gas at room temperature to lie between 2 and 15, in general between 2 and 8 bar, for example between 3 and 5 bar. It is furthermore favorable for lamp life and also for counteracting a decrease in the luminous flux of the lamp caused by blackening of the bulb owing to deposits of tungsten evaporated from the incandescent body when the filling gas comprises Xe, Kr, or a mixture thereof, for example in the ratio in which they are present in the air, i.e. approximately 6% Xe by volume. The evaporation of tungsten is strongly hampered by the high molecular weight of these gases and by their pressure, so that it is possible to use a comparatively small bulb while achieving a high luminous maintenance. This renders it possible to give the lamp a very small constructional height, so that luminaires in which the lamp will be accommodated may be com
REFERENCES:
patent: 4703227 (1987-10-01), Takeda et al.
Bruggemann Ursula
Geboers Jacques M.J.
Kohlmann Wilfried L.
Van Hees Antonius J.M.
Faller F. Brice
Patel Vip
U.S. Philips Corporation
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