(19)

(11)

EP 1 023 523 A1

(12)

(43) Date of publication: 02.08.2000 Bulletin 2000/31 (21) Application number: 98944082.1 (22) Date of filing: 22.09.1998

(51) International Patent Classification (IPC)7: E21B 33/035 (86) International application number: PCT/GB9802/864 (87) International publication number: WO 9920/872 (29.04.1999 Gazette 1999/17)

(84) Designated Contracting States: AT BE DE DK ES FI FR GB IE IT NL PT SE (30) Priority: 17.10.1997 GB 9721929 (71) Applicants: Overfield, Timothy Mark York YO6 6AS (GB) Cumming, Michael York YO6 6AS (GB)	(72) Inventors: Overfield, Timothy Mark York YO6 6AS (GB) Cumming, Michael York YO6 6AS (GB) (74) Representative: Wilson, Peter et al Markgraaf Patents Limited,The Crescent,54 Blossom Street York YO24 1AP York YO24 1AP (GB)