(19)

(11)

EP 0 162 107 A1

(12)

(43) Date of publication: 27.11.1985 Bulletin 1985/48 (21) Application number: 85900310.0 (22) Date of filing: 15.11.1984

(51) International Patent Classification (IPC):  E21B 10/ 12( . ) E21B 10/ 14( . ) (86) International application number: PCT/US1984/001898 (87) International publication number: WO 1985/002223 (23.05.1985 Gazette 1985/12)

(84) Designated Contracting States: AT BE CH DE FR GB LI LU NL SE (30) Priority: 18.11.1983 US 19830553298 (71) Applicant: ROCK BIT INDUSTRIES U.S.A. INC. Fort Worth, TX 76140 (US)	(72) Inventor: GARNER, Lloyd, L. Fort Worth, TX 76109 (US)