(19)

(11)

EP 0 094 939 A1

(12)

(43) Date of publication: 30.11.1983 Bulletin 1983/48 (21) Application number: 82901853.0 (22) Date of filing: 25.06.1982

(51) International Patent Classification (IPC):  A01B 33/ 02( . ) A01B 49/ 02( . ) (86) International application number: PCT/GB1982/000187 (87) International publication number: WO 1983/000001 (06.01.1983 Gazette 1983/01)

(84) Designated Contracting States: DE FR (30) Priority: 25.06.1981 GB 19810019564 (71) Applicant: NATIONAL RESEARCH DEVELOPMENT CORPORATION London SW1E 6SL (GB)	(72) Inventors: PATTERSON, David Eric Ampthill, Bedford (GB) RICHARDSON, Charles David Bromham, Bedford (GB) (74) Representative: Trevor-Briscoe, David William  Patents Department British Technology Group Ltd 101 Newington Causeway London SE1 6BU London SE1 6BU (GB)