Plugging structure for vessels

Details Plugging structure for vessels Plugging structure for vessels

1998-09-24

2000-08-22

Patel, Vip

Electric lamp and discharge devices

With gas or vapor

Having electrode lead-in or electrode support sealed to...

313626, 313623, H01J 1718

Patent

active

061077402

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a sealing part arrangement of various tube lamps, such as a mercury lamp, a metal halide lamp, and halogen lamp and the like.


DESCRIPTION OF RELATED ART

Recently a functional gradient material has been used more and more often for a sealing body of a discharge lamp in which in a silica glass arc tube there is a pair of electrodes opposite one another. In this sealing body one of its ends is rich with a dielectric component such as silicon dioxide or the like, and in the direction to the other end the portion of an electrically conductive component such as molybdenum or the like increases continuously or gradually. In the sealing body consisting of silicon dioxide and molybdenum therefore one end is dielectric and has a coefficient of thermal expansion which is roughly equal to the coefficient of thermal expansion of the silica glass forming the arc tube, while the other end is electrically conductive and has the property that its coefficient of thermal expansion approaches the coefficient of thermal expansion of the tungsten forming the upholding parts of the electrodes. These properties are suitable for a sealing body of a discharge lamp. This sealing body can furthermore be used not only for a discharge lamp, but also for a halogen lamp provided with a luminous filament or halogen heating apparatus provided with a luminous filament.
Since a sealing body using this functional gradient material consists of a dielectric component, such as silicon dioxide or the like, and of an electrically conductive component, such as molybdenum or the like, it however happens that as a result of different coefficients of thermal expansion cracks form in the sealing body when the upholding parts of the electrodes of a metal such as tungsten or the like come into direct contact with the dielectric component. After producing the lamp, the size of these cracks grows; this also leads to failures such as fractures and the like.
To eliminate this defect, for example, in Japanese patent disclosure document HEI 9-125186 it was proposed that within the sealing body the dielectric component and the upholding parts of the electrodes not come into direct contact with one another, but there be gaps or the like present here.
These gaps are however connected to the discharge space and therefore form the coolest portion. When filled substances such as mercury and metal halides condense in this coolest portion, an undesirable phenomenon such as a change of the emission color of the lamp or the like occurs.


DISCLOSURE OF THE INVENTION

With respect to the above described circumstances, as claimed in the invention a sealing part arrangement (hereinafter also called "sealing body") for a tube lamp is given.
(1) In a sealing part arrangement of a tube lamp which seals a side tube which is connected to an arc tube and which securely holds the upholding parts of the electrodes by a shrink seal and which consists of a functional gradient material, in which an electrically conductive component and a dielectric component in the axial direction of the tube have a continuous or gradual concentration gradient, and in which one side is dielectric and the other side is electrically conductive, the invention is characterized in that the upholding parts of the electrodes are located in an opening of the above described functional gradient material without a gap in a shrink seal, and that the surface of the area of the upholding parts of the electrodes which are located in the opening of the functional gradient material is coated at least partially with a thin layer of a metal with a high melting point.
(2) The invention is furthermore characterized in that in the above described design (1) the metal with a high melting point is tungsten or molybdenum.


BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a schematic of a discharge lamp for which sealing bodies as claimed in the invention are used; and
FIG. 2 shows a schematic of the sealing body as claimed in the invention.


BEST MODE FOR CARRYING OUT THE INVENTI

REFERENCES:
patent: 5424609 (1995-06-01), Geven et al.

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