(19)

(11)

EP 0 263 833 A1

(12)

(43) Date of publication: 20.04.1988 Bulletin 1988/16 (21) Application number: 87900226.0 (22) Date of filing: 22.12.1986

(51) International Patent Classification (IPC):  E21B 47/ 12( . ) H04B 5/ 00( . ) (86) International application number: PCT/GB1986/000787 (87) International publication number: WO 1987/004028 (02.07.1987 Gazette 1987/14)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 20.12.1985 GB 19850031368 (71) Applicant: MISSON, Pierre Glasgow G63 9PD (GB)	(72) Inventor: MISSON, Pierre Glasgow G63 9PD (GB)