Electric lamp and discharge devices – Incandescent lamps – Plural filaments or glowers
Reexamination Certificate
2001-03-29
2004-08-31
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Incandescent lamps
Plural filaments or glowers
C313S579000, C313S272000, C313S344000, C313S569000
Reexamination Certificate
active
06784605
ABSTRACT:
This application bases priority on Japanese applications 2000-095806 filed Mar. 30, 2000 and 2000-286218 filed Sep. 20, 2000. The contents of both of these applications are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates to a halogen incandescent lamp using a triple-coiled filament, and a lighting apparatus using the lamp.
2. Description of Related Art
In general, a halogen incandescent lamp utilizes a coiled-coil filament, which is formed into a shorter length than that of a coiled filament. Such a filament, however, is required to be even shorter when it is used in a compact halogen incandescent lamp, for example. In order to shorten the length of a coiled-coil filament, it is known to make a coiled-coiled-coil or a triple-coil filament by winding a coiled-coil filament around a mandrel.
Such a triple-coiled filament can generate radiation close to a point source of visible light. When a lighting apparatus including a reflector is provided with such a halogen incandescent lamp having the triple-coiled filament, it is easy to position the triple-coiled filament around a focus of the reflector. Therefore, visible light generated by the triple-coiled filament is accurately reflected by the reflector. Furthermore, the visible light can accurately irradiate a predetermined area, so that the lighting apparatus has an improved light output ratio. In contrast, the lamp life of such a triple-coiled filament is occasionally short because of sagging and therefore, shorting, during lamp operation.
Japanese Laid Open Utility model Application SHO 58-6369, U.S. Pat. No. 4,499,401 (the '401 patent), and U.S. Pat. No. 4,316,116 (the '116 patent) disclose such a triple-coiled filament for an incandescent lamp. In particular, a triple-coiled filament, described in the '401 patent, has dimensions selected so that it does not require re-crystallization prior to the triple-coiled filament being arranged within the incandescent lamp, simplifying manufacturing. That is, an outer diameter of the triple-coiled filament is in a range of
20
d
to
26
d
, wherein d is a diameter of the tungsten wire. As a result, the triple-coiled filament does not sag during lamp operation, because of its small outer diameter. Therefore, separated windings of the triple-coiled filament do not easily come into contact with each other, avoiding a short circuit. However, when the outer diameter of the triple-coiled filament is in the range of
20
d
to
26
d
, the length of the filament tends to become long because the outer diameter of the filament is shortened. Therefore, it is not easy to apply this filament to a compact halogen incandescent lamp or to position the triple-coiled filament around the focus of the reflector.
Furthermore, the '401 patent explains that the triple-coiled filament of the '116 patent having an outer diameter
27
d
, wherein d is a diameter of a tungsten wire, necessitates a re-crystallization process to eliminate sagging during lamp operation. That is, the grain size of the crystals in the filament grows, so that the re-crystallized triple-coiled filament becomes stronger. However, the elasticity of such a re-crystallized triple-coiled filament decreases excessively, so that it more likely to be damaged by impact. Therefore, when the re-crystallized triple-coiled filament receives an impact from the outside, for example, the re-crystallized triple-coiled filament may vibrate and occasionally break, for example, at the interface of the grains of the crystal.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a halogen incandescent lamp comprises a light-transmitting envelope filled with a gas including a halogen gas and an inert gas. A pair of inner conductive wires are arranged in the envelope. A triple-coiled filament, which has a first coiling, a second coiling, and a third coiling having about 1.5 to about 4 turns, is re-crystallized, arranged in the envelope, and connected between ends of the inner conductive wires. The triple-coiled filament is held by a support member.
According to another aspect of the invention, a lighting apparatus comprises the halogen incandescent lamp described above having a reflector, and a housing accommodating the lamp.
REFERENCES:
patent: 4283653 (1981-08-01), Brett
patent: 4316116 (1982-02-01), Graves et al.
patent: 4686412 (1987-08-01), Johnson, Jr.
Bessho Makoto
Ikejiri Kazuhiro
Mochizuki Hideto
Sakai Makoto
Takahashi Masayuki
Leurig Sharlene
Patel Ashok
Pillsbury & Winthrop LLP
Toshiba Lighting & Technology Corporation
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