(19)

(11)

EP 0 543 806 A1

(12)

(43) Date of publication: 02.06.1993 Bulletin 1993/22 (21) Application number: 90911460.0 (22) Date of filing: 12.07.1990

(51) International Patent Classification (IPC):  B25D 9/ 12( . ) E21B 4/ 14( . ) B25D 9/ 16( . ) (86) International application number: PCT/SE1990/000490 (87) International publication number: WO 1992/001138 (23.01.1992 Gazette 1992/03)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB IT LI LU NL SE (71) Applicant: G-DRILL AB S-11849 Stockholm (SE)	(72) Inventor: GUSTAFSSON, Per CH-1009 Pully (CH) (74) Representative: Aslund, Roland European Patent Attorney  PO Box 99 S-77501 Krylbo S-77501 Krylbo (SE)