Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
1999-09-17
2001-11-06
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
C313S625000, C313S626000, C313S578000, C313S570000
Reexamination Certificate
active
06313582
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a ceramic lamp having a lamp vessel made of translucent ceramic and using a hermetically sealing body of electrically conductive cermet to route current into the lamp vessel, the sealing body being hermetically sealed relative to sealing portions of the lamp vessel via a sealing material.
2. Description of Related Art
In a ceramic lamp, in which the lamp vessel is made of a translucent ceramic and an electrically conductive cermet is used for the hermetically sealing body, and thus current is routed into the lamp vessel, and in which the lamp vessel is hermetically sealed relative to the sealing body using a sealing material, conventionally several sealing processes are performed.
FIG. 11
shows, for example, an arrangement in which a hermetically sealing tube portion
3
is connected on opposite ends of a bulb portion
2
, and the periphery of a hermetically sealing bodies
4
of electrically conductive cermet are sealed relative to the inside wall of the tube portions
3
of the lamp vessel
1
using a sealing material
5
, and thus, hermetically sealed portions
7
are formed. One such lamp is described, for example, in laid-open Japanese Patent Application HEI 8-264155.
Furthermore, a process is known in which, in one of the hermetically sealed ends of a lamp with bilateral hermetic seals (of the double-end type), a hermetically sealing body of electrically conductive cermet and a hermetically sealed tube portion of the lamp vessel are sintered to one another in one part, and in which the other hermetically sealed end, upon evacuation of the lamp, is sealed with a sealing material.
Moreover, a process is known in which thin molybdenum tubes are pushed through the hermetically sealing bodies of electrically conductive cermet, embedded and sintered in part with the lamp vessel, and in which evacuation is performed through the molybdenum tube.
However, if the hermetically sealing bodies of electrically conductive cermet are enclosed with a sealing material in a hermetically sealed tube, there are differences in the coefficients of linear expansion between the respective components of the hermetically sealed portions, i.e., between the hermetically sealed tube, the hermetically sealing body, the sealing material and the electrically conductive supply component, such as the upholding part of the electrode and the like. Therefore, there are cases in which cracks form in these hermetically sealing portions, or as a result of these cracks, leaks occur. In the hermetically sealed portions of a conventional ceramic lamp in which the electrically conductive cermet which is conventionally present is used as the hermetically sealing body, to date sufficiently reliability could not be achieved.
SUMMARY OF THE INVENTION
Therefore, a primary object of the present invention is to provide a ceramic lamp in which the hermetically sealing bodies of electrically conductive cermet in the hermetically sealed tube portion of the lamp vessel are sealed with a sealing material in a manner which reduces the difference of the coefficients of linear expansion between the components of the lamp, and at the same time, and to otherwise insure that the arrangement and material components of the hermetically sealed portions have a high reliability and are tight.
In a discharge lamp of translucent ceramic which has a lamp vessel which has a bulb portion and hermetically sealed tube portion which is connected to the bulb portion, in which furthermore, in the bulb portion, there are electrically conductive supply components, and in which, by seal welding of the hermetically sealing bodies of electrically conductive cermet on the hermetically sealed tube portion with a sealing material, a hermetically sealed arrangement is obtained, the base parts of the above described electrically conductive supply components being inserted into the hermetically sealed bodies of electrically conductive cermet, the indicated object of the invention is obtained by an intermediate layer being formed in the area of the surface layers of the respective hermetically sealing body, the intermediate layer having components of the electrically conductive cermet of the hermetically sealing body intermixed with components of the sealing materials.
The expression “electrically conductive supply component” in a discharge lamp is defined as electrodes and the upholding parts of the electrode, and in an incandescent lamp, such as a halogen lamp or the like, filaments and inner lead pins.
The object is also achieved in accordance with the invention, in a ceramic lamp, by providing the electrically conductive cermet with components which melt at a temperature at which the sealing material melts and welding the hermetically sealing body to the hermetically sealed tube portion.
Furthermore, the object is achieved according to the invention in a ceramic lamp by having the noted intermediate layer have an area with a relatively small concentration gradient which is formed by a diffusion of the components of the sealing material into the intermediate layer and an area with a steep concentration gradient thereof.
Additionally, the object is advantageously achieved in accordance with the invention by the intermediate layer being an area with a thickness of at least 20 microns in which the concentration of the components of the sealing material is at least half the concentration in the pure sealing material.
Here, the expression “area of the intermediate layer with a thickness . . . ” is defined mainly as the area in which the surface layers of the electrically conductive cermet are caused to melt, and in this way, components of the sealing material in a larger amount are able to diffuse into the molten material. This thickness, furthermore, represents the distance from a position at the outer surface of the cermet before seal welding to the inside as far as the position where the concentration of the components, which are distributed in the intermediate layer and which are contained in the sealing material, however are not contained in the electrically conductive cermet, reaches ½ of the initial concentration of these components in the sealing material.
The object is advantageously achieved in accordance with the invention especially in that the sealing material and the electrically conductive cermet contain the same component, specifically silicon dioxide.
Still further, the object is advantageously achieved according to the invention, in a ceramic lamp, by the sealing material filling at least a gap between inside faces of the hermetically sealing body and bordering outside faces of the hermetically sealed tube of the lamp vessel.
The object is also advantageously achieved in accordance with the invention, in a ceramic lamp, in that the surface of the electrically conductive cermet which faces outward of the lamp is at least partially covered with the sealing material.
Additionally, the object is advantageously achieved according to the invention, in a ceramic lamp, by the following conditions being met at the same time:
|&agr;
1
−&agr;
2
|≦1×10
−6
(1/K)
|&agr;
2
−&agr;
3
|≦1×10
−6
(1/K)
|&agr;
3
−&agr;
1
|≦1×10
−6
(1/K)
where &agr;
1
, &agr;
2
, and &agr;
3
are, respectively, the average coefficients of linear expansion of the ceramic of the lamp vessel, the electrically conductive cermet of the hermetically sealing body and the sealing materials at 25° C. to 350° C.
Furthermore, the object is advantageously achieved in accordance with the invention by holes of the hermetically sealing body of electrically conductive cermet into which the base parts of the electrically conductive supply components are inserted each having a widened entry opening.
The object is also advantageously achieved according to the invention, in a ceramic lamp, by the condition |y−u|×d≦1.2×10
−9
(m/K) being met where d (m) is the diameter of
Ikeuchi Mitsuru
Miyanaga Shouji
Mori Kazuyuki
Tagawa Yukiharu
Nixon & Peabody LLP
Patel Ashok
Safran David S.
Ushiodenki Kabushiki Kaisha
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