Halogen incandescent lamp with heat transfer by conduction

Details Halogen incandescent lamp with heat transfer by conduction Halogen incandescent lamp with heat transfer by conduction

1996-06-13

1999-04-20

Patel, Vip

Electric lamp and discharge devices

With gas or vapor

Incandescent filament lamp

313579, 313628, 313631, H01K 150

Patent

active

058960074

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to incandescent halogen lamps closed on one end, particularly for general lighting (AB), but also for photographic or projection purposes (FO) or other applications. In particular, it is applicable to low-voltage lamps with low power, but it can also be used for high- and medium-voltage lamps.


BACKGROUND

Lamps of the type to which the invention relates are known for instance from German Patent Disclosure DE-OS 22 31 520. Their cold fill pressure is typically approximately 5 to 15 atm of an inert gas, predominantly noble gases (argon, krypton, xenon), which optionally have a slight proportion (5 to 10%) of nitrogen. Traces of one or more halogen compounds are also added, whose partial pressure amounts to only a few millibars.
In such lamps, predominantly for general lighting purposes, the attainment of a relatively long service life (AB: 2000 hours, FO 200 hours and more) is a major goal. To achieve this, the assumption is generally made that the evaporation rate of the tungsten material of the luminous element must be damped by means of the highest possible fill pressure (in halogen lamps approximately 2.7 to 10.7 bar (approximately 2000 Torr), according to H. particularly page 35. At the same time, the halogen compound present as a fill component, with the aid of the convection occurring in the bulb, supports a cycle process for the tungsten particles evaporating from the luminous element (S. M. Correra, Int. J. Heat Mass Transfer 30, p. 663, 1987). However, the convection also causes a considerable heat loss, which is on the order of magnitude of 10% of the lamp power.
In general, it has until now been considered indispensible to maintain such operating conditions, in order to be able to achieve a high light yield (up to 25 lm/W) with a simultaneously high lamp life (at least 2000 hours).
For special reasons, it is true that special lamps with a low cold fill pressure have been individually developed (European Patent Disclosure DE-A 295 592), but on the precondition that nevertheless the convection that drives the halogen cycle takes place. A further example of this is French Patent Disclosure FR-A 2 436 495. It describes a photographic lamp pinched on both ends, in which the cold fill pressure is lowered to about 0.2 bar in order to reduce the risk of explosion. This is achieved at the usual cost of reducing the service life. Moreover, in U.S. Pat. No. 4,463,277, an incandescent halogen lamp with a cold fill pressure of about 0.8 to 0.93 bar is described. The low pressure is intended to enable the use of hard glass.
An essential role in the theoretical discussion of incandescent lamps is played by the concept of the Langmuir layer, which has been explained in detail, for instance in Techn. Wissenschaftl. Abhandlungen der OSRAM GmbH 125-136, 1967, Springer-Verlag, Berlin. Here the existence of a horizontal stationary gas layer, in fact the Langmuir layer, adjacent to the luminous element, which is considered to be a cylinder, is assumed, and is observed to be homogeneous and of constant diameter. In it, heat removal takes place solely by heat dissipation, while outside this layer the heat losses are determined by free convection. In incandescent halogen lamps, the Langmuir layer thickness is on the order of magnitude of a few millimeters (see also the aforementioned German Patent Disclosure DE-OS 22 31 520). It is dependent on the fill pressure.
From European Patent Disclosure EP-A 0 241 911, an incandescent halogen lamp with a luminous element with a wire diameter on the order of magnitude of 100 .mu.m is known.
Special conditions pertain in soffit lamps, that is, elongated incandescent lamps pinched on both ends with an axially arranged luminous element. Here, if there is a deviation from the horizontal position (and particularly in a vertical burning position), severe problems arise in operation, having to do with the demixing that occurs between the fill gas and the halogen additive inside the bulb. In U.S. Pat. No. 3,435,272 and in an article in Illum

REFERENCES:
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patent: 3626236 (1971-12-01), Robinson et al.
patent: 4280076 (1981-07-01), Walsh
patent: 4338540 (1982-07-01), Sovilla
patent: 4463277 (1984-07-01), DeCaro
patent: 4480212 (1984-10-01), Monahanet et al.
patent: 4524302 (1985-06-01), Berlec
patent: 4703220 (1987-10-01), Walsh
patent: 4959585 (1990-09-01), Hoegler
patent: 4965485 (1990-10-01), Tarumi et al.
Int. J. Heat Mass Transfer, vol. 30, No. 4, pp. 663-672, 1987, article by M. Corea: "Fluid flow and heat transfer in incandescent lamps".
"Technisch-wissenschaftliche Abhandlungen der Osram-Gesellschaft" ("Technological-scientific papers of the Osram Company"), vol. 9, published by Springer, Berlin Heidelberg New York, 1967, article by H. Schirmer, I. Stober and J. Friedrich: "Uber die Methode von Langmuir zur theoretischen Behandlung gasgefullter Gluhlampen" ("With regard to the method of Langmuir for the theoretical treatment of gas-filled incandescent lamps"), pp. 125-136.

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