(19)

(11)

EP 0 208 770 A1

(12)

(43) Date of publication: 21.01.1987 Bulletin 1987/04 (21) Application number: 86900913.0 (22) Date of filing: 15.01.1986

(51) International Patent Classification (IPC):  E21B 47/ 18( . ) F04B 9/ 111( . ) (86) International application number: PCT/US1986/000049 (87) International publication number: WO 1986/004383 (31.07.1986 Gazette 1986/17)

(84) Designated Contracting States: AT BE CH DE FR GB IT LI LU NL SE (30) Priority: 16.01.1985 US 19850692319 05.08.1985 US 19850762426 (71) Applicant: BIRDWELL, J.C. Houston, TX 77061 (US)	(72) Inventor: BIRDWELL, J.C. Houston, TX 77061 (US) (74) Representative: Patentanwälte Grünecker, Kinkeldey, Stockmair & Partner  Maximilianstrasse 58 D-80538 München D-80538 München (DE)