(19)

(11)

EP 0 077 336 A1

(12)

(43) Date of publication: 27.04.1983 Bulletin 1983/17 (21) Application number: 82901041.0 (22) Date of filing: 26.03.1982

(51) International Patent Classification (IPC):  E21B 17/ 042( . ) (86) International application number: PCT/SE1982/000091 (87) International publication number: WO 1982/003653 (28.10.1982 Gazette 1982/26)

(84) Designated Contracting States: AT DE FR GB (30) Priority: 24.04.1981 SE 19810002626 (71) Applicant: Fagersta AB S-773 01 Fagersta (SE)	(72) Inventor: GUSTAFSSON, Gösta Christer S-778 00 Norberg (SE) (74) Representative: Uusitalo, Isak  Carminger, Uusitalo & Nyberg Patentbyra AB, P.O. Box 7274 S-103 89 Stockholm S-103 89 Stockholm (SE)