Compact coiled coil incandescent filament using pitch for sag control

(19)

(11)

EP 0 271 859 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	09.05.1990 Bulletin 1990/19

(43)	Date of publication A2:
	22.06.1988 Bulletin 1988/25

(21)	Application number: 87118491.7

(22)	Date of filing: 14.12.1987

(51)	International Patent Classification (IPC)⁴: H01K 1/14, H01K 1/18

(84)	Designated Contracting States:
	BE DE FR GB NL

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Priority:

16.12.1986 US 942332

(71)	Applicant: GTE PRODUCTS CORPORATION
	Wilmington Delaware 19801 (US)

(72)	Inventor:
	Johnson, Pierce, Jr. Topsfield, MA 01983 (US)

(74)	Representative: Butler, Michael John
	Frank B. Dehn & Co., European Patent Attorneys, 179 Queen Victoria Street London EC4V 4EL London EC4V 4EL (GB)

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References cited: :

(54)	Compact coiled coil incandescent filament using pitch for sag control

(57) This invention provides an improved compact fine wire incandescent lamp filament and method for making the same. The filament has a primary mandrel ratio in the range of about 1.40 to about 3.00 and a secondary mandrel ratio which in the range of about 3.0 to about 10.0.
The improved filament design exhibits an increase in compactness and retains or increases structural rigidity while exhibiting minimal sag when the filament is incorporated into an incandescent lamp of the tungsten halogen type variety.
The compact coiling method is particularly useful in designing compact filaments for high voltage applications where it is desirable to eliminate the use of rectifying means to lower the effective voltage across the filament.

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