(19)

(11)

EP 0 853 521 A1

(12)

(43) Date of publication: 22.07.1998 Bulletin 1998/30 (21) Application number: 96917192.0 (22) Date of filing: 04.06.1996

(51) International Patent Classification (IPC):  B23B 51/ 00( . ) E21B 10/ 44( . ) B23P 15/ 32( . ) E21B 10/ 58( . ) (86) International application number: PCT/US1996/008927 (87) International publication number: WO 1996/040461 (19.12.1996 Gazette 1997/03)

(84) Designated Contracting States: DE FR (30) Priority: 07.06.1995 US 19950475034 19.10.1995 US 19950545272 (71) Applicant: CREDO TOOL COMPANY Woodburn, OR 97071 (US)	(72) Inventor: SCHIMKE, Thomas, O. Louisville, KY 40243 (US) (74) Representative: Grünecker, Kinkeldey, Stockmair & Schwanhäusser Anwaltssozietät  Maximilianstrasse 58 80538 München 80538 München (DE)