(19)

(11)

EP 0 537 156 A1

(12)

(43) Date of publication: 21.04.1993 Bulletin 1993/16 (21) Application number: 91907630.0 (22) Date of filing: 02.04.1991

(51) International Patent Classification (IPC):  H01T 13/ 32( . ) H01T 21/ 02( . ) H01T 13/ 39( . ) (86) International application number: PCT/US1991/002239 (87) International publication number: WO 1991/015887 (17.10.1991 Gazette 1991/24)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU NL SE (30) Priority: 04.04.1990 GB 19900007659 (71) Applicant: Cooper Industries Inc. Houston TX 77210 (US)	(72) Inventor: LENK, Michael B-3090 Overijse (BE) (74) Representative: MacDougall, Donald Carmichael  Cruikshank & Fairweather 19 Royal Exchange Square Glasgow G1 3AE, Scotland Glasgow G1 3AE, Scotland (GB)