(19)

(11)

EP 0 532 647 A1

(12)

(43) Date of publication: 24.03.1993 Bulletin 1993/12 (21) Application number: 91911481.0 (22) Date of filing: 05.06.1991

(51) International Patent Classification (IPC):  A01H 4/ 00( . ) (86) International application number: PCT/GB1991/000895 (87) International publication number: WO 1991/018499 (12.12.1991 Gazette 1991/28)

(84) Designated Contracting States: BE CH DE DK FR GB IT LI NL (30) Priority: 07.06.1990 GB 19900012708 (71) Applicant: BRITISH TECHNOLOGY GROUP LTD London SE1 6BU (GB)	(72) Inventors: BILLINGTON, William Peter Flitwick, Bedfordshire MK45 1LP (GB) GRUNDON, Peter Michael Haynes, Bedfordshire MK45 3QQ (GB) (74) Representative: Laight, Martin Harvey, et al  W.H. Beck, Greener & Co. 7 Stone Buildings Lincoln's Inn London WC2A 3SZ London WC2A 3SZ (GB)