(19)

(11)

EP 0 277 169 A1

(12)

(43) Date of publication: 10.08.1988 Bulletin 1988/32 (21) Application number: 87904924.0 (22) Date of filing: 03.08.1987

(51) International Patent Classification (IPC):  E21B 47/ 12( . ) H01F 38/ 14( . ) (86) International application number: PCT/GB1987/000554 (87) International publication number: WO 1988/001096 (11.02.1988 Gazette 1988/04)

(84) Designated Contracting States: DE FR GB NL (30) Priority: 07.08.1986 GB 19860019316 (71) Applicant: CONTROLOGY PRODUCTS LIMITED East Kilbride, Glasgow G75 0TF (GB)	(72) Inventors: HALE, John, Christopher East Kilbride Glasgow G75 8BJ (GB) HALE, Christopher, Charles, Harold Dunfermline Fife KY11 3AJ (GB) (74) Representative: Wotherspoon, Graham  FITZPATRICKS 4 West Regent Street Glasgow G2 1RS Scotland Glasgow G2 1RS Scotland (GB)