Double-end type metal halide bulb with low power consumption

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(11)

EP 0 978 864 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	21.11.2001 Bulletin 2001/47

(43)	Date of publication A2:
	09.02.2000 Bulletin 2000/06

(21)	Application number: 99115050.9

(22)	Date of filing: 04.08.1999

(51)	International Patent Classification (IPC)⁷: H01J 61/073, H01J 61/82, H01J 61/86

(84)	Designated Contracting States:
	AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU MC NL PT SE
	Designated Extension States:
	AL LT LV MK RO SI

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Priority:

04.08.1998 JP 22047098

(71)	Applicant: Stanley Electric Co., Ltd.
	Meguro-ku Tokyo 153-8636 (JP)

(72)	Inventors:
	Shibayama, Shigeru Aoba-ku, Yokohama-shi, Kanagawa-ken (JP) Nagahara, Toshiyuki Aoba-ku, Yokohama-shi, Kanagawa-ken (JP) Muto, Masaaki Aoba-ku, Yokohama-shi, Kanagawa-ken (JP) Iritono, Kimihiro Aoba-ku, Yokohama-shi, Kanagawa-ken (JP)

(74)	Representative: Wagner, Karl H., Dipl.-Ing. et al
	WAGNER & GEYER Patentanwälte Gewürzmühlstrasse 5 80538 München 80538 München (DE)

(54)	Double-end type metal halide bulb with low power consumption

(57) The double end type Scl₃-Nal metal halide lamp with rated power consumption smaller than 35 W, more specifically 20-30 W, of the present invention comprises a pair of electrodes (20) whose diameter ⊘ n is equal to or smaller than 0.25mm (⊘n ≤ 0.25 mm), and the diameter ⊘ P of the electrode tip portion (5) is equal to or larger than the diameter ⊘ S of the remaining electrode portion (⊘P ≥ ⊘S). The electrode tip portion (5) is spherical or cylindrical, and the cross section area of the electrode (20) increases as a cross section moves toward the tip portion (5) for mitigating thermal emission from the electrode tip portion (5) and preventing low light emission efficiency due to small input power. The arc chamber (6) is substantially a sphere, elliptic, or any similar shape to them, and comprises the pair of electrodes (20), mercury, rare gas, and at least one kind of metal halide sealed therein. Since rare gas, more specifically Xenon gas, is sealed within an arc chamber (6) in high pressure, when applied excessive current, instant lumen output is achieved.

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