(19)

(11)

EP 0 061 494 A1

(12)

(43) Date of publication: 06.10.1982 Bulletin 1982/40 (21) Application number: 81902877.0 (22) Date of filing: 05.10.1981

(51) International Patent Classification (IPC):  E21B 43/ 24( . ) E21B 36/ 02( . ) (86) International application number: PCT/US1981/001331 (87) International publication number: WO 1982/001214 (15.04.1982 Gazette 1982/10)

(84) Designated Contracting States: DE FR GB NL (30) Priority: 07.10.1980 US 19800194820 28.08.1981 US 19810296321 28.08.1981 US 19810296322 (60) Divisional application: 86105864.2 / 0200195 (71) Applicant: FOSTER-MILLER ASSOCIATES, INC. Waltham, MA 02154 (US)	(72) Inventors: BURRILL, Charles E., Jr. Billerica, MA 01821 (US) SMIRLOCK, Martin E. Brimfield, MA 01010 (US) KREPCHIN, Ira P. Newton Upper Falls, MA 02164 (US) DOHERTY, Brian, J. Marblehead, MY 01945 (US) (74) Representative: Heidrich, Udo, Dr. jur., Dipl.-Phys.  Rechtsanwalt & Patentanwalt Dipl.-Phys. Dr. jur. U. HEIDRICH Franziskanerstrasse 30 D-81669 München D-81669 München (DE)