(19)

(11)

EP 0 263 106 A1

(12)

(43) Date of publication: 13.04.1988 Bulletin 1988/15 (21) Application number: 86904038.0 (22) Date of filing: 20.06.1986

(51) International Patent Classification (IPC):  E21D 9/ 12( . ) (86) International application number: PCT/AU1986/000183 (87) International publication number: WO 1987/000237 (15.01.1987 Gazette 1987/01)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 08.07.1985 AU 19850001360 (71) Applicant: BURTENSHAW PTY. LTD. Perth, Western Australia (AU)	(72) Inventor: ROBERTS, William Michael Balga W.A. (AU) (74) Representative: Pacitti, Pierpaolo A.M.E.  Murgitroyd and Company 373 Scotland Street Glasgow G5 8QA Glasgow G5 8QA (GB)