(19)
(11) EP 0 335 617 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
20.03.1991 Bulletin 1991/12

(43) Date of publication A2:
04.10.1989 Bulletin 1989/40

(21) Application number: 89302961.1

(22) Date of filing: 23.03.1989
(51) International Patent Classification (IPC)4: H05B 3/26, H05B 3/74
(84) Designated Contracting States:
AT BE CH DE ES FR GB GR IT LI LU NL SE

(30) Priority: 25.03.1988 GB 8807139

(71) Applicant: THORN EMI plc
London W1A 2AY (GB)

(72) Inventor:
  • Balderson, Simon Neville
    Nr. Reading, Berkshire, (GB)

(74) Representative: Marsh, Robin Geoffrey et al
THORN EMI Patents Limited Central Research Laboratories Dawley Road
Hayes, Middlesex UB3 1HH
Hayes, Middlesex UB3 1HH (GB)


(56) References cited: : 
   
       


    (54) Current source limitation for thick film heating elements


    (57) A heating element (1) comprises a plurality of thick film electrically resistive tracks (2, 4, 6), of which at least one has a temperature coefficient of resistance in excess of 0.006 per degree C. A first track (2) is for electrical connection to a power supply. Means (12, 14) for electrically connecting the first track (2) to a second track (4, 6) comprise a component which depends on temperature such that, in use, the current flowing in the second track (4, 6) increases with the temperature of the first track (2).







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