(19)

(11)

EP 0 163 727 A1

(12)

(43) Date of publication: 11.12.1985 Bulletin 1985/50 (21) Application number: 85900342.0 (22) Date of filing: 29.11.1984

(51) International Patent Classification (IPC):  E21B 10/ 38( . ) E21B 10/ 58( . ) (86) International application number: PCT/US1984/001949 (87) International publication number: WO 1985/002442 (06.06.1985 Gazette 1985/13)

(84) Designated Contracting States: AT BE CH DE FR GB LI LU NL SE (30) Priority: 29.11.1983 US 19830556005 (71) Applicant: GRAESSLE, Clement F. Mt. Clemens, MI 48043 (US)	(72) Inventor: McKNIGHT, Herman Romeo, MI 48065 (US)