(19)

(11)

EP 0 536 287 A1

(12)

(43) Date of publication: 14.04.1993 Bulletin 1993/15 (21) Application number: 91912790.0 (22) Date of filing: 27.06.1991

(51) International Patent Classification (IPC):  A01H 4/ 00( . ) (86) International application number: PCT/GB1991/001043 (87) International publication number: WO 1992/000004 (09.01.1992 Gazette 1992/02)

(84) Designated Contracting States: BE CH DE DK FR GB IT LI NL (30) Priority: 28.06.1990 GB 19900014387 (71) Applicant: BRITISH TECHNOLOGY GROUP LTD London SE1 6BU (GB)	(72) Inventors: DAVIS, Paul Frank Upper Gravenhurst, Bedfordshire MK45 4HY (GB) TILLETT, Robin Deirdre Flitwick, Bedfordshire MK45 1AE (GB) MARCHANT, John, Arthur Bedford MK41 8DB (GB) (74) Representative: Laight, Martin Harvey  W.H. Beck, Greener & Co. 7 Stone Buildings Lincoln's Inn London WC2A 3SZ London WC2A 3SZ (GB)