(19)

(11)

EP 0 523 101 A1

(12)

(43) Date of publication: 20.01.1993 Bulletin 1993/03 (21) Application number: 91906825.0 (22) Date of filing: 22.03.1991

(51) International Patent Classification (IPC):  G01P 15/ 13( . ) (86) International application number: PCT/GB1991/000436 (87) International publication number: WO 1991/015774 (17.10.1991 Gazette 1991/24)

(84) Designated Contracting States: DE ES FR GB IT SE (30) Priority: 03.04.1990 GB 19900007483 (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)