Electric lamp and discharge devices – With gas or vapor – Having electrode lead-in or electrode support sealed to...
Reexamination Certificate
1998-11-12
2001-07-17
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With gas or vapor
Having electrode lead-in or electrode support sealed to...
C313S318070, C313S026000, C313S315000
Reexamination Certificate
active
06262534
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a lamp of the type having a light source including a bulb having a pair of outer leads extending therefrom, a glass envelope surrounding the light source, and a glass stem fixed to the glass envelope. A pair of input leads sealed in the glass stem are electrically connected to the outer leads of the light source. More particularly, the invention relates to a lamp having a protective shroud surrounding the light source.
U.S. Pat. No. 5,670,840 discloses a lamp having a tungsten halogen light source with a filament connected to electrodes connected to metal foils in pinches at opposite ends of a bulb, and outer leads connected to the foils. The outer leads are welded to mounting legs sealed in the glass stem, the mounting legs serving as input leads. One of the mounting legs supports a tubular shroud of glass or quartz which surrounds the light source and protects the glass envelope from fragments in the event of bulb failure. The shroud is fixed to the mounting leg by means of glass connector brackets adjacent opposed open ends of the tube.
The lamp described in U.S. Pat. No. 5,670,840 requires connecting the shroud to a mounting leg at two places by relatively fragile glass connections, subsequently welding the outer leads of the light source to the mounting legs, followed by sealing the mounting leg to the stem.
U.S. Pat. No. 4,888,517 in
FIG. 6
discloses a metal halide light source having a pair of electrodes connected to metal foils in a pinch at one end of the bulb, and side-by-side outer leads connected to the foils. The outer leads are welded to input leads sealed in the glass stem. A glass shroud surrounds the light source, the shroud having a cylindrical wall, an open end toward the stem, and an opposed closed end. The shroud is supported by mounting legs which are also welded to respective input leads, the legs being fixed to metal straps surrounding the shroud adjacent respective ends. While the closed end of the shroud provides additional protection for the envelope in the event of bulb failure, multiple welding steps are required to connect the light source to the input leads and to complete the shroud support. Further, since it is necessary to support the shroud by means of a strap adjacent the closed end, the corresponding leg must be loaded against the lamp envelope for stability.
It would be desirable to provide a unified mount structure for supporting the light source, and further to provide simplified and reliable means for positioning a protective shroud about the light source.
SUMMARY OF THE INVENTION
According to the invention, the outer leads extending from the bulb of the light source are sealed directly to the glass stem without any intervening welds. The outer leads are thus one and the same as the input leads sealed in the glass stem.
The invention is most applicable for outer leads which extend in parallel from a pinch at one end of the bulb.
According to another aspect of the invention, a protective shroud surrounding the light source is supported by a metal member having a lower end fixed to one of the leads, and an upper end fixed to a strap surrounding the shroud. The shroud is preferably in the form of a glass vial having a substantially cylindrical wall, an open end adjacent to the stem, an opposite closed end, and a circumferential constriction in the wall adjacent to the open end. The support strap is seated in the circumferential constriction, providing good vertical positioning for the shroud. The metal member may be extended to an additional strap positioned around the upper end of the shroud for improved lateral stability.
A vial having a circumferential constriction is a readily available staple in commerce, thus providing failure protection which is both economic and simple to fix to the support structure.
According to another embodiment, a pair of horseshoe-shaped mounts with mutually opposed concavities are welded to respective leads between the light source and the stem, and a protective glass shroud has a circumferential constriction which is formed into the concavities. The shroud is conveniently a small test tube which is placed about the light source and heated, causing it to shrink into the concavities.
It is also possible to shrink the shroud directly against the pinch sealing the outer leads of the light source, avoiding the need for individual shroud supports fixed to the leads. The shroud preferably converges from the cylindrical portion all the way to the open end so that it also engages the outer leads. This embodiment provides good stability at low cost.
The mount structure of the invention thus provides a simple but sturdy support for both the light source and the shroud by sealing the outer leads of the light source directly to the stem.
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Heijmans Chris
Johnson, Jr. Pierce
Morrell Mark
Gerike Matthew J.
Halajian Dicran
Patel Ashok
Philips Electronics North America Corp.
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