(19)

(11)

EP 0 546 050 A1

(12)

(43) Date of publication: 16.06.1993 Bulletin 1993/24 (21) Application number: 91915976.0 (22) Date of filing: 06.09.1991

(51) International Patent Classification (IPC):  E21B 17/ 00( . ) G07F 7/ 10( . ) E21B 17/ 046( . ) (86) International application number: PCT/GB1991/001523 (87) International publication number: WO 1992/004525 (19.03.1992 Gazette 1992/07)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU NL SE (30) Priority: 07.09.1990 GB 19900019554 (71) Applicant: FRAMO DEVELOPMENTS (U.K.) LIMITED London SW20 OAY (GB)	(72) Inventor: MOHN, Frank London SW20 0AY (GB) (74) Representative: Jones, Ian  W.P. THOMPSON & CO. Celcon House 289-293 High Holborn London WC1V 7HU London WC1V 7HU (GB)