(19)

(11)

EP 0 506 728 A1

(12)

(43) Date of publication: 07.10.1992 Bulletin 1992/41 (21) Application number: 91900820.0 (22) Date of filing: 21.12.1990

(51) International Patent Classification (IPC):  G01R 21/ 133( . ) (86) International application number: PCT/FI1990/000312 (87) International publication number: WO 1991/010146 (11.07.1991 Gazette 1991/15)

(84) Designated Contracting States: AT CH DE DK ES FR GB IT LI NL SE (30) Priority: 22.12.1989 FI 19890006216 (71) Applicant: VALTION TEKNILLINEN TUTKIMUSKESKUS SF-02150 Espoo 15 (FI)	(72) Inventor: SEPPÄ, Heikki SF-02150 Espoo (FI) (74) Representative: Smulders, Theodorus A.H.J., Ir., et al  Vereenigde Octrooibureaux Nieuwe Parklaan 97 NL-2587 BN 's-Gravenhage NL-2587 BN 's-Gravenhage (NL)