(19)

(11)

EP 0 223 813 A1

(12)

(43) Date of publication: 03.06.1987 Bulletin 1987/23 (21) Application number: 86903493.0 (22) Date of filing: 30.05.1986

(51) International Patent Classification (IPC):  G01F 25/ 00( . ) (86) International application number: PCT/GB1986/000305 (87) International publication number: WO 1986/007146 (04.12.1986 Gazette 1986/26)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 31.05.1985 GB 19850013783 (71) Applicant: SKELTONHALL LIMITED Sheffield S4 7SD (GB)	(72) Inventors: PIX, Keith, Anthony Sheffield S11 7AQ (GB) SPENCER, Colin, John Derbyshire S44 5XF (GB) HALL, Anthony Sheffield (GB) (74) Representative: Garratt, Peter Douglas, et al  Mathys & Squire 100 Grays Inn Road London WC1X 8AL London WC1X 8AL (GB)