(19)
(11) EP 0 271 857 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
16.05.1990 Bulletin 1990/20

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

(21) Application number: 87118489.1

(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

(30) Priority: 16.12.1986 US 942339

(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)


(56) References cited: : 
   
       


    (54) Compact coiled coil incandescent filament with supports


    (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 4.00 and a secondary mandrel ratio which is greater than or equal to the primary mandrel ratio. The length between supports is kept less than or equal to 20 times the secondary diameter.
    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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