(19)

(11)

EP 0 505 423 A1

(12)

(43) Date of publication: 30.09.1992 Bulletin 1992/40 (21) Application number: 91900875.0 (22) Date of filing: 11.12.1990

(51) International Patent Classification (IPC):  G01P 15/ 09( . ) G01P 21/ 00( . ) (86) International application number: PCT/GB1990/001931 (87) International publication number: WO 1991/009315 (27.06.1991 Gazette 1991/14)

(84) Designated Contracting States: AT BE CH DE DK ES FR GB GR IT LI LU NL SE (30) Priority: 11.12.1989 GB 19890027927 (71) Applicant: KELLETT, Micheal, Andrew Stevenage, Hertfordshire SG1 4HA (GB)	(72) Inventor: KELLETT, Micheal, Andrew Stevenage, Hertfordshire SG1 4HA (GB) (74) Representative: Russell-Rayner, Albert Patrick  Business Centre Avenue One Business Park Letchworth Garden City Hertfordshire SG6 2HB Letchworth Garden City Hertfordshire SG6 2HB (GB)